Ambac Financial (AMBC) 10-K27 Feb 242023 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2023	Feb. 26, 2024	Jun. 30, 2023	Apr. 30, 2013
Entity Information [Line Items]
Document Type	10-K
Document Quarterly Report	true
Document Period End Date	Dec. 31, 2023
Entity File Number	1-10777
Entity Registrant Name	AMBAC FINANCIAL GROUP, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	13-3621676
Entity Address, Address Line One	One World Trade Center
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10007
City Area Code	(212)
Local Phone Number	658-7470
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	AMBC
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Document Transition Report	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		45,195,370
Common Stock, Par or Stated Value Per Share				$ 0.01
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Central Index Key	0000874501
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Public Float			$ 623,109,150
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Documents Incorporated by Reference	Portions of the Registrant’s Proxy Statement related to its annual meeting of stockholders are incorporated by reference in this Form 10-K in response to Part III Items 10, 11, 12, 13, and 14.

Audit Information

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2023
Document And Entity Information [Abstract]
Auditor Name	KPMG LLP
Auditor Location	New York, NY
Auditor Firm ID	185

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Assets:
Available-for-sale Securities	$ 1,710	$ 1,395
Debt Securities, Trading and Available-for-Sale	27	59
Short-term Investments	426	507
Other Investments	475	568
Investments, Total	2,664	2,593
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	28	44
Restricted Cash	12	14
Premiums Receivable, Net	290	269
Reinsurance Recoverables, Including Reinsurance Premium Paid	195	115
Deferred ceded premium	204	124
Deferred Policy Acquisition Cost	11	3
Subrogation recoverable	137	271
Derivative assets	26	27
Intangible assets, less accumulated amortization	307	326
Goodwill	70	61
Other assets	129	112
Total assets	8,428	7,973
Liabilities:
Unearned premiums	422	372
Liability for Claims and Claims Adjustment Expense	893	805
Ceded premiums payable	90	39
Capitalized Contract Cost, Net	6	5
Long-term debt	508	639
Accrued interest payable	475	427
Derivative liabilities	35	38
Other liabilities	199	201
Liabilities	$ 6,997	$ 6,647
Preferred Stock, Shares Outstanding	0	0
Preferred stock, shares authorized	20,000,000	20,000,000
Stockholders’ equity:
Preferred Stock, Value, Issued	$ 0	$ 0
Common Stock, Value, Issued	0	0
Additional paid-in capital	292	274
Accumulated other comprehensive income (loss)	(160)	(253)
Retained earnings	1,246	1,245
Treasury Stock, Value	(17)	(15)
Total Ambac Financial Group, Inc. stockholders’ equity	1,362	1,252
Nonredeemable noncontrolling interest	53	53
Total stockholders’ equity	$ 1,415	$ 1,305
Preferred stock, par value	$ 0.01
Common stock, shares issued	46,659,144	46,658,990
Common stock, shares authorized	130,000,000	130,000,000
Redeemable Noncontrolling Interest, Equity, Carrying Amount	$ 17	$ 20
Total liabilities, redeemable noncontrolling interest and stockholders’ equity	$ 8,428	$ 7,973
Treasury Stock, Common, Shares	1,463,774	1,685,233
Variable Interest Entity [Member]
Assets:
Available-for-sale Securities	$ 2,167	$ 1,967
Restricted Cash	246	17
Loans, at fair value	1,663	1,829
Derivative and other assets	318	241
Derivative assets	226	239
Other assets	92	2
Total assets	4,394	4,054
Variable interest entity assets:
Loans, at fair value	1,663	1,829
Liabilities:
Long-term debt	2,967	3,107
Derivative liabilities	1,197	1,048
Other Sundry Liabilities, Current	240
Other liabilities	5	5
Liabilities	4,404	4,160
Stockholders’ equity:
Long-term Debt	2,710	2,788
Collateral Pledged [Member]
Assets:
Available-for-sale Securities	27	64
Short-term Investments	$ 27	$ 64

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Fixed income securities, amortized cost	$ 2,197	$ 2,041
Short-term investments, amortized cost	426	507
Other Investment Not Readily Marketable, Fair Value	463	556
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	0
Uncollectable premium receivables	4	5
Reinsurance Recoverable, Allowance for Credit Loss	$ 0	$ 0
Preferred stock, par value	$ 0.01
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred Stock, Shares Outstanding	0	0
Common stock, shares authorized	130,000,000	130,000,000
Common stock, shares issued	46,659,144	46,658,990
Common Stock, Shares, Outstanding	45,195,370
Treasury Stock, Common, Shares	1,463,774	1,685,233
Collateral Pledged [Member]
Short-term investments, amortized cost	$ 27	$ 64
Short-term Investments [Member]
Fixed income securities, amortized cost	426	507
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Short-term Investments [Member] \| Collateral Pledged [Member]
Fixed income securities, amortized cost	27	64
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Variable Interest Entity, Primary Beneficiary [Member]
Long-term Debt	2,710	2,788
Parent Company [Member]
Fixed income securities, amortized cost	14	13
Short-term investments, amortized cost	156	175
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Parent Company [Member] \| Short-term Investments [Member]
Fixed income securities, amortized cost	$ 156	$ 175

Consolidated Statements of Tota

Consolidated Statements of Total Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Net premiums earned	$ 78	$ 56	$ 47
Insurance Commissions and Fees	51	31	26
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	8	3	0
Net investment income:
Net investment income	140	17	139
Realized Investment Gains (Losses)	(22)	31	7
Derivative, Gain (Loss) on Derivative, Net	(1)	129	22
Net realized gains on extinguishment of debt	0	81	33
Other income	11	10	1
Income (loss) on variable interest entities	3	21	7
Gain (Loss) Related to Litigation Settlement		126	0
Total revenues and other income	269	505	282
Policyholder Benefits and Claims Incurred, Net	(33)
Expenses:
Losses and loss adjustment expenses		(396)	(88)
Deferred Policy Acquisition Costs, Amortization Expense	11	3	1
Insurance Commissions	29	18	15
Intangible amortization	29	47	55
General and Administrative Expense	156	141	111
Interest expense	64	168	187
Total expenses	257	(20)	281
Pretax income (loss)	12	525	2
Provision (benefit) for income taxes	7	2	18
Net income	5	522	(16)
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	(1)	(1)	(1)
Net income (loss) attributable to common stockholders	4	522	(17)
Other comprehensive income (loss), after tax
Net income	5	522	(16)
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Reclassification Adjustment from AOCI for Derecognition, after Tax	0	0	(1)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	2	(1)	(1)
Total other comprehensive income (loss), net of income tax	93	(310)	(21)
Total comprehensive income, net of income tax	98	212	(38)
Less: net (gain) loss attributable to noncontrolling interest
Total comprehensive income attributable to common stockholders	$ 96	$ 212	$ (38)
Basic	$ 0.18	$ 11.48	$ (0.61)
Diluted	$ 0.18	$ 11.31	$ (0.61)
Weighted Average Number of Shares Outstanding, Basic	45,636,649	45,719,906	46,535,001
Weighted Average Number of Shares Outstanding, Diluted	46,540,706	46,414,830	46,535,001
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	$ (1)	$ (1)	$ (1)
AMPS Gain on Purchase of Shares		1
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	51	(225)	(12)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	$ 40	$ (85)	$ (8)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Noncontrolling Interest [Member]	Treasury Stock, Common	Parent Company [Member]	Parent Company [Member] Accounting Standards Update 2016-13 [Member]	Parent Company [Member] Retained Earnings [Member]	Parent Company [Member] Retained Earnings [Member] Accounting Standards Update 2016-13 [Member]	Parent Company [Member] AOCI Attributable to Parent [Member]	Parent Company [Member] Additional Paid-in Capital [Member]	Parent Company [Member] Treasury Stock, Common
Beginning balance at Dec. 31, 2020	$ 1,140	$ 759	$ 79	$ 0	$ 0	$ 242	$ 60	$ (1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	(38)	(17)	(21)						$ (38)		$ (17)		$ (21)
Effect of New Accounting Principle										$ 0		$ 0
Stock-based compensation	14					14			14					$ 14
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	(6)	(4)						(2)	(6)		(4)				$ (2)
Ending balance at Dec. 31, 2021	1,098	726	58	0	0	257	60	(3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Noncontrolling Interest, Change in Redemption Value	(12)	(12)
Total comprehensive income (loss)	212	521	(310)						211		521		(310)
Stock-based compensation	17					17			17					17	0
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	(4)	(5)				0		2	(4)		(5)				2
Treasury Stock, Value, Acquired, Cost Method	14							14
Ending balance at Dec. 31, 2022	1,305	1,245	(253)	0	0	274	53	(15)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest, Total, Excluding Gain on AMPS Repurchase	211
Noncontrolling Interest, Change in Redemption Value	3	3							3		3
Proceeds from Noncontrolling Interests	2						2
AMPS Impact on Stockholders Equity	(8)	1					(9)
Total comprehensive income (loss)	98	4	93						96		4		$ 93
Stock-based compensation	17					17			17					$ 17
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	(5)	(8)						3	(5)		(8)				3
Treasury Stock, Value, Acquired, Cost Method	(5)							(5)	5						$ 5
Ending balance at Dec. 31, 2023	1,415	1,246	(160)	0	0	292	53	(17)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest, Total, Excluding Gain on AMPS Repurchase	96
Noncontrolling Interest, Change in Redemption Value	$ 5	$ 5	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 5		$ 5

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net income (loss) attributable to common stockholders	$ 4	$ 522	$ (17)
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	(1)	(1)	(1)
AMPS Gain on Purchase of Shares		1
Net income	5	522	(16)
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	2	2	2
Amortization of bond premium and discount	(15)	(11)	(13)
Share-based compensation	17	17	14
Unearned premiums, net	(30)	(58)	(82)
Losses and loss expenses, net	130	1,220	(147)
Ceded premiums payable	52	6	6
Premium receivables	(21)	54	48
Accrued interest payable	(1)	(134)	103
Amortization of intangible assets	29	47	55
Net investment gains (losses), including impairments	22	(31)	(7)
Net realized gains (losses) on extinguishment of debt	0	(81)	(33)
Income (loss) on variable interest entities	3	21	7
Other, net	13	(196)	(56)
Net cash provided by operating activities	200	1,335	(131)
Cash flows from investing activities:
Proceeds from sales of bonds	140	523	236
Proceeds from matured bonds	74	206	698
Purchases of bonds	(415)	(403)	(343)
Proceeds from sales of other invested assets	209	166	39
Purchases of other invested assets	(80)	(112)	(127)
Change in short-term investments	118	(52)	98
Change in cash collateral	(42)	44	9
Proceeds From Financial Guaranty Variable Interest Entity Assets	199	504	171
Payments to Acquire Businesses, Net of Cash Acquired	(7)	(18)	0
Other, net	6	9	(5)
Net cash provided by investing activities	435	866	776
Cash flows from financing activities:
Proceeds from Sale of Senior Surplus Notes			11
Proceeds from Issuance of Secured Debt			1,163
Proceeds from (Payments to) Noncontrolling Interests	(2)	(1)	(1)
Paydown of Ambac Note			(1,641)
Payments of Debt Issuance Costs			(12)
Payments for Repurchase of Common Stock	(5)	(14)
Payment, Tax Withholding, Share-based Payment Arrangement	(5)	(4)	(6)
Paydown of Financial Guaranty Variable Interest Entity Liabilities	(315)	(591)	(170)
Net Cash Provided by (Used in) Financing Activities	(423)	(2,163)	(657)
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Continuing Operations	1	(1)	0
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	213	38	(12)
Supplemental disclosure of cash flow information
Income Taxes Paid	11	6	15
Cash payments related to reorganization items:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	274	61	23
AMPS Exchange Cash Paid		(8)
Sitka AAC Note
Cash payments related to reorganization items:
Repayments of Secured Debt		1,210
5.1 % Surplus Notes Due 2020 [Member]
Cash payments related to reorganization items:
Payments for purchase of surplus notes	0	(191)
Tier 2 Notes [Member]
Cash payments related to reorganization items:
Repayments of Secured Debt	97	143
Ambac Financial Group, Inc Parent Company Only [Member]
Cash flows from operating activities:
Net income (loss) attributable to common stockholders	4	522	(17)
Net income	4	522	(17)
Adjustments to reconcile net income to net cash used in operating activities:
Amortization of bond premium and discount	0	(7)	(9)
Share-based compensation	9	12	14
Net investment gains (losses), including impairments	0	14	5
Other, net	2	1	(6)
Net cash provided by operating activities	2	46	(10)
Cash flows from investing activities:
Proceeds from matured bonds	0	68	33
Purchases of bonds	(1)	(1)	(34)
Proceeds from sales of other invested assets	(3)	(4)	(8)
Change in short-term investments	20	(51)	105
Net cash provided by investing activities	16	12	95
Cash flows from financing activities:
Payments for Repurchase of Common Stock	5	14
Net Cash Provided by (Used in) Financing Activities	(21)	(57)	(92)
Supplemental disclosure of cash flow information
Income Taxes Paid	0	0	0
Variable Interest Entity [Member]
Adjustments to reconcile net income to net cash used in operating activities:
Net investment gains (losses), including impairments	(1)	(2)	(2)
Cash flows from investing activities:
Change in cash collateral	$ 235	$ 0	$ 0

Background and Business Descrip

Background and Business Description	12 Months Ended
Background and Business Description	Dec. 31, 2023
Accounting Policies [Abstract]
Background and Business Description	1. BACKGROUND AND BUSINESS DESCRIPTION Ambac Financial Group, Inc. (“AFG”), headquartered in New York City, is a financial services holding company incorporated in the state of Delaware on April 29, 1991. References to “Ambac,” the “Company,” “we,” “our,” and “us” are to AFG and its subsidiaries, as the context requires. Ambac's business operations include: • Legacy Financial Guarantee Insurance — Ambac's financial guarantee business includes the activities of Ambac Assurance Corporation ("AAC") and its wholly owned subsidiaries, including Ambac Assurance UK Limited (“Ambac UK”) and Ambac Financial Services LLC ("AFS"). Both AAC and Ambac UK have financial guarantee insurance portfolios that have been in runoff since 2008. AFS provided interest rate derivatives to financial guarantee customers and used derivatives to hedge interest rate risk in AAC's insurance and investment portfolios. Since June 2023, AFS' only remaining derivative positions include a limited number of legacy customer swaps and their associated hedges. • Specialty Property and Casualty Insurance — Ambac's Specialty Property and Casualty Insurance program business includes five admitted carriers and an excess and surplus lines (“E&S” or “nonadmitted”) insurer (collectively, “Everspan”). Everspan carriers have an AM Best rating of 'A-' (Excellent). • Insurance Distribution — Ambac's specialty property and casualty ("P&C") insurance distribution business, which currently includes Managing General Agents and Underwriters (collectively "MGAs") and insurance brokers. Currently includes (i) Xchange Benefits, LLC (“Xchange”), a P&C MGA specializing in accident and health products, (ii) All Trans Risk Solutions, LLC ("All Trans"), an MGA specializing in specialty commercial automobile insurance for specific "for-hire" auto classes, (iii) Capacity Marine Corporation ("Capacity Marine"), a wholesale and retail brokerage and reinsurance intermediary specializing in marine and international risk, and (iv) Riverton Insurance Agency, Corp. ("Riverton"), which was acquired on August 1, 2023, an insurance services business specializing in professional liability lines and consisting of an MGA and a retail agency. Both All Trans and Capacity Marine Corporation were acquired in November 2022. Beginning in 2022, the Company began reporting these three business operations as segments; see Note 3. Segment Information for further information. Limitations on Voting and Transfer of Common Stock AFG’s Amended and Restated Certificate of Incorporation limits voting and transfer rights of stockholders in significant ways. Article IV contains voting restrictions applicable to any person owning at least 10% of AFG's common stock so that such person (including any group consisting of such person and any other person with whom such person or any affiliate or associate of such person has any agreement, contract, arrangement or understanding with respect to acquiring, voting, holding or disposing of AFG’s common stock) shall not be entitled to cast votes in excess of one vote less than 10% of the votes entitled to be cast by all common stock holders, except as otherwise approved by the OCI (as defined below). Article XII contains substantial restrictions on the ability to transfer AFG’s common stock. In order to preserve certain tax benefits, subject to limited exceptions, any attempted transfer of common stock shall be prohibited and void to the extent that, as a result of such transfer (or any series of transfers of which such transfer is a part), either (i) any person or group of persons shall become a holder of 5% or more of AFG’s common stock or (ii) the percentage stock ownership interest in AFG of any holder of 5% or more of AFG’s common stock shall be increased (a “Prohibited Transfer”). These restrictions shall not apply to an attempted transfer if the transferor or the transferee obtains the written approval of AFG’s Board of Directors to such transfer. A purported transferee of a Prohibited Transfer shall not be recognized as a stockholder of AFG for any purpose whatsoever in respect of the securities which are the subject of the Prohibited Transfer (the “Excess Securities”). Until the Excess Securities are acquired by another person in a transfer that is not a Prohibited Transfer, the purported transferee of a Prohibited Transfer shall not be entitled with respect to such Excess Securities to any rights of stockholders of AFG, including, without limitation, the right to vote such Excess Securities and to receive dividends or distributions, whether liquidating or otherwise, in respect thereof, if any. Once the Excess Securities have been acquired in a transfer that is not a Prohibited Transfer, the securities shall cease to be Excess Securities. If the Board determines that a transfer of securities constitutes a Prohibited Transfer then, upon written demand by AFG, the purported transferee shall transfer or cause to be transferred any certificate or other evidence of ownership of the Excess Securities within the purported transferee’s possession or control, together with any distributions paid by AFG with respect to such Excess Securities, to an agent designated by AFG. Such agent shall thereafter sell such Excess Securities and the proceeds of such sale shall be distributed as set forth in the Amended and Restated Certificate of Incorporation. If the purported transferee of a Prohibited Transfer has resold the Excess Securities before receiving such demand, such person shall be deemed to have sold the Excess Securities for AFG’s agent and shall be required to transfer to such agent the proceeds of such sale, which shall be distributed as set forth in the Amended and Restated Certificate of Incorporation. Strategies to Enhance Shareholder Value The Company's primary goal is to maximize long-term shareholder value through the execution of targeted strategies for its (i) Specialty Property and Casualty Insurance and Insurance Distribution businesses and (ii) Legacy Financial Guarantee Insurance business. Specialty Property and Casualty Insurance and Insurance Distribution strategic priorities include: • Growing our Specialty Property and Casualty Insurance business to generate underwriting profits from a diversified portfolio of commercial and personal liability risks accessed primarily through program administrators. • Expanding our Insurance Distribution business based on deep domain knowledge in specialty and niche classes of risk which generate attractive margins at scale. This will be achieved through acquisitions, establishing new businesses “de-novo,” and organic growth and diversification supported by a centralized technology led shared services offering. • Making opportunistic investments that are strategic to both the Specialty Property and Casualty Insurance and Insurance Distribution businesses. Legacy Financial Guarantee Insurance strategic priorities include: • Actively managing, de-risking and mitigating insured portfolio risk, and pursuing recoveries of previously paid losses. • Improving operating efficiency and optimizing our asset and liability profile. • Exploring strategic options to further maximize value for AFG. The execution of Ambac’s strategy to increase the value of its investment in AAC is subject to the restrictions set forth in the Settlement Agreement, dated as of June 7, 2010, as amended (the "Settlement Agreement"), by and among AAC, Ambac Credit Products LLC ("ACP"), AFG and certain counterparties to credit default swaps with ACP that were guaranteed by AAC, as well as the Stipulation and Order among the OCI, AFG and AAC that became effective on February 22, 2024 (the “Stipulation and Order”), replacing the Stipulation and Order that became effective on February 12, 2018, as amended (the "2018 Stipulation and Order"), each of which requires OCI and, under certain circumstances contemplated by the Settlement Agreement, holders of surplus notes, to approve certain actions taken by or in respect of AAC. In exercising its approval rights, OCI will act for the benefit of policyholders, and will not take into account the interests of AFG. The Settlement Agreement limits certain activities of AAC and its subsidiaries, such as issuing indebtedness; engaging in mergers and similar transactions; disposing of assets; making restricted payments; creating or permitting liens; engaging in transactions with affiliates; modifying or creating tax sharing agreements; and taking certain actions with respect to surplus notes (among other restrictions and limitations). The Settlement Agreement includes certain allowances with respect to these activities and generally requires the approval of OCI and, in some cases, holders of surplus notes issued pursuant to the Settlement Agreement, for consents, waivers or amendments. The Stipulation and Order requires AAC to maintain a level of surplus and contingency reserves as regards policyholders which provide reasonable security against contingencies affecting AAC’s financial position that are not otherwise fully covered by reserves or reinsurance; discount loss reserves in a manner approved by OCI; maintain OCI’s Runoff Capital Framework according to parameters specified by OCI; pay the costs of consultants and other experts retained by OCI; limit affiliate transactions and the payment of any dividend or other distribution without the prior non-disapproval of OCI; notify OCI of events that would or would be reasonably likely to cause a material adverse effect to AAC or its affiliates; obtain OCI’s non-disapproval to exercise certain control rights with respect to certain policies that were previously allocated to the Segregated Account of AAC; obtain OCI’s approval for non-ordinary course transactions involving consideration to be paid by AAC of $100 or more; and obtain OCI’s approval of any changes to AAC’s investment policy or derivative use plan. The Stipulation and Order also requires AFG to use its best efforts to preserve the use of NOLs for the benefit of AAC and its subsidiaries. The Stipulation and Order differs from the 2018 Stipulation and Order in that the 2018 Stipulation and Order (i) did not refer to OCI’s Runoff Capital Framework; (ii) included certain affirmative covenants concerning books and records, and reporting of information or events, that were not included in the Stipulation and Order; and (iii) contained a more restrictive limitation on transactions with affiliates. The Stipulation and Order has no fixed term and may be terminated or modified only with the approval of OCI. OCI reserved the right to modify or terminate the Stipulation and Order in a manner consistent with the interests of policyholders, creditors and the public generally. The execution of Ambac’s strategy to increase the value of its investment in AAC may be affected by a new capital framework developed and implemented by OCI to assist OCI with making decisions related to capital management at AAC ("OCI's Runoff Capital Framework"). OCI’s Runoff Capital Framework applies risk-based and other adjustments to AAC’s assets and insured liabilities, as determined by OCI in its sole discretion. OCI’s Runoff Capital Framework allows AAC to understand the likely impact of various developments and actions now or in the future on AAC’s capital position thereunder. No changes in AAC’s current management of the business are required by OCI’s Runoff Capital Framework. AAC’s ability to use capital for potential future deleveraging transactions or distributions will require AAC to sustain an excess of risk-adjusted assets over risk-adjusted insured liabilities according to OCI’s Runoff Capital Framework, and to obtain OCI’s approval, and there can be no assurance that OCI will approve any such use of capital. The results of OCI’s Runoff Capital Framework are expected to vary over time based on changes in AAC’s financial position, insured portfolio developments, the impact of strategic actions taken by AAC, the impact of asset/liability management by AAC and, possibly, changes to the inputs and assumptions utilized by OCI. Opportunities for remediating losses on poorly performing insured transactions depend on market conditions, including the perception of AAC’s creditworthiness, the structure of the underlying risk and associated policy as well as other counterparty specific factors. AAC's ability to commute policies or purchase certain investments may also be limited by available liquidity. Settlement of RMBS Litigations and Redemption of Secured Notes: In October 2022, AAC entered into a Settlement Agreement and Release (the “BOA Settlement Agreement”) with Bank of America Corporation and certain affiliates thereof (together, the “BOA Parties”) pursuant to which the BOA Parties paid AAC the sum of $1,840 (the “BOA Settlement Payment”) following the dismissal of AAC’s lawsuits against the BOA Parties concerning certain residential mortgage-backed securities (“RMBS”) trusts, and the withdrawal by AAC of its objections, including any pending appeals, concerning the settlements that were the subject of certain trust instructional proceedings. In exchange for the BOA Settlement Payment, AAC, on its own behalf and on behalf of its affiliates, agreed to release the BOA Parties and related parties (the “Released Parties”) from claims asserted or which could have been asserted in AAC’s pending litigations against the BOA Parties as well as claims that AAC and its affiliates ever had, may currently have or may have in the future against the Released Parties, subject to certain limited exceptions. The BOA Settlement Agreement also requires AAC to dismiss other pending claims against the Released Parties, and to generally refrain from, and in certain situations hold the Released Parties harmless with respect to, certain actions taken by AAC with respect to RMBS trusts created prior to the date of the BOA Settlement Agreement involving the Released Parties. The BOA Settlement Payment included recoveries from litigations for alleged breaches of contractual obligations and fraud by the BOA Parties. Management allocated the BOA Settlement Payment to each of the litigations based on previously developed valuations of each individual litigation. The portion of the BOA Settlement Payment allocated to fraud litigation recoveries has been recorded as a litigation recovery in the Statement of Comprehensive Income (Loss). On December 29, 2022, AAC entered into a Settlement Agreement and Release (the “Nomura Settlement Agreement”) with Nomura Credit & Capital, Inc. (“Nomura”) to settle its litigation against Nomura concerning certain RMBS trusts (the “Trusts”). Pursuant to the Nomura Settlement Agreement, Nomura made a cash payment to AAC of $140 (the "Nomura Settlement Payment"), and AAC and Nomura agreed to release each other and their respective affiliates and related persons from any claims relating to the Trusts, the financial guaranty policies issued by AAC in connection with Trusts (other than AAC’s obligations to pay insurance claims under such policies), the securities related to the Trusts, and the mortgage loans related to the Trusts. The Nomura Settlement Payment received in January 2023 reduced the subrogation recoverable asset on the Consolidated Balance Sheet. During 2022 and 2023, AAC wholly redeemed its secured debt, in accordance with the terms of such debt, utilizing the BOA Settlement Payment, the Nomura Settlement Payment and other resources as further discussed in Note 12. Long-term Debt . Impact to the Consolidated Statement of Comprehensive Income (Loss): The total gain recognized in net income attributable to common stockholders related to entering into the BOA Settlement Agreement and the Nomura Settlement Agreement, including the redemption of the Sitka AAC Note following receipt of the BOA Settlement Payment, was as follows: Year Ended December 31, 2022 Losses and loss benefit (1) $ 362 Litigation recoveries 126 Net realized gains (losses) on extinguishment of debt (53) Net investment gains (losses), including impairments 5 Impact to net income attributable to common stockholders $ 440 (1) 2022 losses and loss benefit relating to R&W recoveries were $123.
Settlement of RMBS Litigation and Redemption of Secured Notes	Settlement of RMBS Litigations and Redemption of Secured Notes: In October 2022, AAC entered into a Settlement Agreement and Release (the “BOA Settlement Agreement”) with Bank of America Corporation and certain affiliates thereof (together, the “BOA Parties”) pursuant to which the BOA Parties paid AAC the sum of $1,840 (the “BOA Settlement Payment”) following the dismissal of AAC’s lawsuits against the BOA Parties concerning certain residential mortgage-backed securities (“RMBS”) trusts, and the withdrawal by AAC of its objections, including any pending appeals, concerning the settlements that were the subject of certain trust instructional proceedings. In exchange for the BOA Settlement Payment, AAC, on its own behalf and on behalf of its affiliates, agreed to release the BOA Parties and related parties (the “Released Parties”) from claims asserted or which could have been asserted in AAC’s pending litigations against the BOA Parties as well as claims that AAC and its affiliates ever had, may currently have or may have in the future against the Released Parties, subject to certain limited exceptions. The BOA Settlement Agreement also requires AAC to dismiss other pending claims against the Released Parties, and to generally refrain from, and in certain situations hold the Released Parties harmless with respect to, certain actions taken by AAC with respect to RMBS trusts created prior to the date of the BOA Settlement Agreement involving the Released Parties. The BOA Settlement Payment included recoveries from litigations for alleged breaches of contractual obligations and fraud by the BOA Parties. Management allocated the BOA Settlement Payment to each of the litigations based on previously developed valuations of each individual litigation. The portion of the BOA Settlement Payment allocated to fraud litigation recoveries has been recorded as a litigation recovery in the Statement of Comprehensive Income (Loss). On December 29, 2022, AAC entered into a Settlement Agreement and Release (the “Nomura Settlement Agreement”) with Nomura Credit & Capital, Inc. (“Nomura”) to settle its litigation against Nomura concerning certain RMBS trusts (the “Trusts”). Pursuant to the Nomura Settlement Agreement, Nomura made a cash payment to AAC of $140 (the "Nomura Settlement Payment"), and AAC and Nomura agreed to release each other and their respective affiliates and related persons from any claims relating to the Trusts, the financial guaranty policies issued by AAC in connection with Trusts (other than AAC’s obligations to pay insurance claims under such policies), the securities related to the Trusts, and the mortgage loans related to the Trusts. The Nomura Settlement Payment received in January 2023 reduced the subrogation recoverable asset on the Consolidated Balance Sheet. During 2022 and 2023, AAC wholly redeemed its secured debt, in accordance with the terms of such debt, utilizing the BOA Settlement Payment, the Nomura Settlement Payment and other resources as further discussed in Note 12. Long-term Debt . Impact to the Consolidated Statement of Comprehensive Income (Loss): The total gain recognized in net income attributable to common stockholders related to entering into the BOA Settlement Agreement and the Nomura Settlement Agreement, including the redemption of the Sitka AAC Note following receipt of the BOA Settlement Payment, was as follows: Year Ended December 31, 2022 Losses and loss benefit (1) $ 362 Litigation recoveries 126 Net realized gains (losses) on extinguishment of debt (53) Net investment gains (losses), including impairments 5 Impact to net income attributable to common stockholders $ 440 (1) 2022 losses and loss benefit relating to R&W recoveries were $123.
Strategies to Enhance Shareholder Vakye	Strategies to Enhance Shareholder Value The Company's primary goal is to maximize long-term shareholder value through the execution of targeted strategies for its (i) Specialty Property and Casualty Insurance and Insurance Distribution businesses and (ii) Legacy Financial Guarantee Insurance business. Specialty Property and Casualty Insurance and Insurance Distribution strategic priorities include: • Growing our Specialty Property and Casualty Insurance business to generate underwriting profits from a diversified portfolio of commercial and personal liability risks accessed primarily through program administrators. • Expanding our Insurance Distribution business based on deep domain knowledge in specialty and niche classes of risk which generate attractive margins at scale. This will be achieved through acquisitions, establishing new businesses “de-novo,” and organic growth and diversification supported by a centralized technology led shared services offering. • Making opportunistic investments that are strategic to both the Specialty Property and Casualty Insurance and Insurance Distribution businesses. Legacy Financial Guarantee Insurance strategic priorities include: • Actively managing, de-risking and mitigating insured portfolio risk, and pursuing recoveries of previously paid losses. • Improving operating efficiency and optimizing our asset and liability profile. • Exploring strategic options to further maximize value for AFG. The execution of Ambac’s strategy to increase the value of its investment in AAC is subject to the restrictions set forth in the Settlement Agreement, dated as of June 7, 2010, as amended (the "Settlement Agreement"), by and among AAC, Ambac Credit Products LLC ("ACP"), AFG and certain counterparties to credit default swaps with ACP that were guaranteed by AAC, as well as the Stipulation and Order among the OCI, AFG and AAC that became effective on February 22, 2024 (the “Stipulation and Order”), replacing the Stipulation and Order that became effective on February 12, 2018, as amended (the "2018 Stipulation and Order"), each of which requires OCI and, under certain circumstances contemplated by the Settlement Agreement, holders of surplus notes, to approve certain actions taken by or in respect of AAC. In exercising its approval rights, OCI will act for the benefit of policyholders, and will not take into account the interests of AFG. The Settlement Agreement limits certain activities of AAC and its subsidiaries, such as issuing indebtedness; engaging in mergers and similar transactions; disposing of assets; making restricted payments; creating or permitting liens; engaging in transactions with affiliates; modifying or creating tax sharing agreements; and taking certain actions with respect to surplus notes (among other restrictions and limitations). The Settlement Agreement includes certain allowances with respect to these activities and generally requires the approval of OCI and, in some cases, holders of surplus notes issued pursuant to the Settlement Agreement, for consents, waivers or amendments. The Stipulation and Order requires AAC to maintain a level of surplus and contingency reserves as regards policyholders which provide reasonable security against contingencies affecting AAC’s financial position that are not otherwise fully covered by reserves or reinsurance; discount loss reserves in a manner approved by OCI; maintain OCI’s Runoff Capital Framework according to parameters specified by OCI; pay the costs of consultants and other experts retained by OCI; limit affiliate transactions and the payment of any dividend or other distribution without the prior non-disapproval of OCI; notify OCI of events that would or would be reasonably likely to cause a material adverse effect to AAC or its affiliates; obtain OCI’s non-disapproval to exercise certain control rights with respect to certain policies that were previously allocated to the Segregated Account of AAC; obtain OCI’s approval for non-ordinary course transactions involving consideration to be paid by AAC of $100 or more; and obtain OCI’s approval of any changes to AAC’s investment policy or derivative use plan. The Stipulation and Order also requires AFG to use its best efforts to preserve the use of NOLs for the benefit of AAC and its subsidiaries. The Stipulation and Order differs from the 2018 Stipulation and Order in that the 2018 Stipulation and Order (i) did not refer to OCI’s Runoff Capital Framework; (ii) included certain affirmative covenants concerning books and records, and reporting of information or events, that were not included in the Stipulation and Order; and (iii) contained a more restrictive limitation on transactions with affiliates. The Stipulation and Order has no fixed term and may be terminated or modified only with the approval of OCI. OCI reserved the right to modify or terminate the Stipulation and Order in a manner consistent with the interests of policyholders, creditors and the public generally. The execution of Ambac’s strategy to increase the value of its investment in AAC may be affected by a new capital framework developed and implemented by OCI to assist OCI with making decisions related to capital management at AAC ("OCI's Runoff Capital Framework"). OCI’s Runoff Capital Framework applies risk-based and other adjustments to AAC’s assets and insured liabilities, as determined by OCI in its sole discretion. OCI’s Runoff Capital Framework allows AAC to understand the likely impact of various developments and actions now or in the future on AAC’s capital position thereunder. No changes in AAC’s current management of the business are required by OCI’s Runoff Capital Framework. AAC’s ability to use capital for potential future deleveraging transactions or distributions will require AAC to sustain an excess of risk-adjusted assets over risk-adjusted insured liabilities according to OCI’s Runoff Capital Framework, and to obtain OCI’s approval, and there can be no assurance that OCI will approve any such use of capital. The results of OCI’s Runoff Capital Framework are expected to vary over time based on changes in AAC’s financial position, insured portfolio developments, the impact of strategic actions taken by AAC, the impact of asset/liability management by AAC and, possibly, changes to the inputs and assumptions utilized by OCI. Opportunities for remediating losses on poorly performing insured transactions depend on market conditions, including the perception of AAC’s creditworthiness, the structure of the underlying risk and associated policy as well as other counterparty specific factors. AAC's ability to commute policies or purchase certain investments may also be limited by available liquidity.

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies (Notes)	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Significant Accounting Policies	2. BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES Ambac’s consolidated financial statements have been prepared on the basis of U.S. generally accepted accounting principles (“GAAP”). The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and disclosures. There can be no assurance that actual results will conform to such estimates and any future changes in estimates could be material to the financial statements. Consolidation The consolidated financial statements include the accounts of AFG and all other entities in which AFG (directly or through its subsidiaries) has a controlling financial interest, including variable interest entities (“VIEs”) for which AFG or an AFG subsidiary is deemed the primary beneficiary in accordance with the Consolidation Topic of the Accounting Standards Codification ("ASC"). All significant intercompany balances have been eliminated. The usual condition for a controlling financial interest is ownership of a majority of the voting interests of an entity. However, a controlling financial interest may also exist in entities, such as VIEs, through arrangements that do not involve controlling voting interests. A VIE is an entity: a) that lacks enough equity investment at risk to permit the entity to finance its activities without additional subordinated financial support from other parties; or b) where the group of equity holders does not have: (1) the power, through voting rights or similar rights, to direct the activities of an entity that most significantly impact the entity’s economic performance; (2) the obligation to absorb the entity’s expected losses; or (3) the right to receive the entity’s expected residual returns. The determination of whether a variable interest holder is the primary beneficiary involves performing a qualitative analysis of the VIE that includes, among other factors, its capital structure, contractual terms including the rights of each variable interest holder, the activities of the VIE, whether the variable interest holder has the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance, whether the variable interest holder has the obligation to absorb losses of the VIE that could potentially be significant to the VIE or the right to receive benefits from the VIE that could potentially be significant to the VIE, related party relationships and the design of the VIE. An entity that is deemed the primary beneficiary of a VIE is required to consolidate the VIE. See Note 11. Variable Interest Entities , for a detailed discussion of Ambac’s involvement in VIEs, Ambac’s methodology for determining whether Ambac is required to consolidate a VIE and the effects of VIEs being consolidated and deconsolidated. AFG Unconsolidated Financial Information Financial information of AFG is presented in Schedule II in this Annual Report on Form 10-K as of December 31, 2023 and 2022 and for the years ended December 31, 2023, 2022 and 2021. Investments in subsidiaries are accounted for using the equity method of accounting in Schedule II. Measurement of Credit Losses on Financial Instruments (CECL) Ambac measures credit losses on financial assets that are not accounted for at fair value through net income in accordance with the Current Expected Credit Loss standard or "CECL". • The CECL impact on available-for-sale debt securities is discussed in the Investments sub-section below. • The CECL impact on amortized cost assets, including contract assets and receivables accounted for under the ASC 606 revenue recognition standard, is addressed in the Premiums, Reinsurance Recoverables, Loans and Revenue Recognition sub-sections below. These amortized cost assets reflect management's current estimate of all expected lifetime credit losses. The estimate of expected lifetime credit losses considers historical information, current information, as well as reasonable and supportable forecasts. Expected lifetime credit losses for amortized cost assets are recorded as an allowance for credit losses, with subsequent increases or decreases in the allowance reflected in net income each period. CECL does not apply to subrogation recoveries of previously paid and unpaid losses on insurance contracts accounted for under ASC 944 nor does it apply to equity method investments accounted for under ASC 323. Investments The Investments - Debt Securities Topic of the ASC requires that all debt instruments be classified in Ambac’s Consolidated Balance Sheets according to their purpose and, depending on that classification, be carried at either cost or fair market value. Ambac’s non-VIE debt investment portfolio is accounted for on a trade-date basis and consists primarily of: • Investments in fixed maturity securities are either classified as available-for-sale or trading as defined by the Investments - Debt Securities Topic of the ASC. Available-for-sale debt securities are reported in the financial statements at fair value with unrealized gains and losses, net of deferred taxes, reflected in Accumulated Other Comprehensive Income (Loss) in Stockholders’ Equity and computed using amortized cost as the basis. For purposes of computing amortized cost, premiums and discounts are accounted for using the effective interest method over the term of the security. For structured debt securities with a large underlying pool of homogenous loans, such as mortgage-backed and asset-backed securities, premiums and discounts are adjusted for the effects of actual and anticipated prepayments. For other fixed maturity securities, such as corporate and municipal bonds, discounts are amortized or accreted over the remaining term of the securities and premiums are amortized to the earliest call date. Investments in fixed maturity securities classified at trading are reported in the financial statements at fair value with unrealized gains and losses included in Net investment income on the Statement of Total Comprehensive Income (Loss). • Equity interests in pooled investment funds which are accounted for in accordance with the Investments - Equity Securities Topic of the ASC and reported as Other investments on the Consolidated Balance Sheet with income reported through Net investment income on the Statement of Total Comprehensive Income (Loss). Equity interests in the form of common stock or in-substance common stock are classified as trading securities and reported at fair value while limited partner interests in such funds are reported using the equity method. • Preferred equity investments that do not have readily determinable fair values and are carried at cost, less any impairments as permitted under the Investments — Equity Securities Topic of the ASC. VIE investments in fixed maturity securities are carried at fair value as they are classified as either available-for-sale or trading as defined by the Investments — Debt Securities Topic of the ASC, or accounted for under the fair value option election. For additional information about VIE investments, including fair value by asset-type, see Note 11. Variable Interest Entities . Fair value is based primarily on quotes obtained from independent market sources. When quotes for fixed maturity securities are not available or cannot be reasonably corroborated, valuation models are used to estimate fair value. These models include estimates, made by management, which utilize current market information. When fair value is not readily determinable for pooled investment funds, the investments are valued using net asset value ("NAV") as a practical expedient as permitted under the Fair Value Measurement Topic of the ASC. Investment valuations could differ materially from amounts that would actually be realized in the market. Realized gains and losses on the sale of investments are determined on the basis of specific identification. Refer to Note 5. Fair Value Measurements for further description of the methodologies used to determine the fair value of investments, including model inputs and assumptions where applicable. Ambac has a formal impairment review process for fixed maturity available-for-sale securities in its investment portfolio. Ambac conducts a review each quarter to identify and evaluate investments that have indications of impairment in accordance with the Investments - Debt Securities Topic of the ASC. If management either: (i) has the intent to sell its investment in an impaired debt security or (ii) determines that the Company more likely than not will be required to sell the debt security before its anticipated recovery of the amortized cost basis less any current period credit impairment, then an impairment charge is recognized in earnings, with the amortized cost of the security written-down to fair value. If management does not intend to sell, or will not be required to sell the debt security, the security is reviewed for credit impairment. Factors considered to identify and assess securities for credit impairment include: (i) fair values that have declined by 20% or more below amortized cost; (ii) recent downgrades by rating agencies; (iii) the financial condition of the issuer and financial guarantor, as applicable, and an analysis of projected defaults on the underlying collateral; and (iv) whether scheduled interest payments are past due. The recognition of credit impairment losses for available-for-sale debt securities are recorded as an allowance for credit losses with an offsetting charge to net income. Improvements to estimated credit losses for available-for-sale debt securities are recognized immediately in net income. If we believe a decline in the fair value of a particular fixed maturity available-for-sale investment is not credit impaired, we record the decline as an unrealized loss net of tax in Accumulated Other Comprehensive Income (Loss) in Stockholders’ Equity on our Consolidated Balance Sheets. The evaluation of securities for credit impairment is a quantitative and qualitative process, which is subject to risks and uncertainties and is intended to determine whether, and to what extent, declines in the fair value of investments should be recognized in current period earnings. The risks and uncertainties include changes in general economic conditions, the issuer’s or guarantor’s financial condition and/or future prospects, the impact of regulatory actions on the investment portfolio, the performance of the underlying collateral, the effects of changes in interest rates or credit spreads and the expected recovery period. With respect to Ambac insured securities owned, future cash flows used to measure credit impairment represents the sum of (i) the bond’s intrinsic cash flows and (ii) the estimated AAC claim payments. Ambac’s assessment about whether a decline in value is considered a credit impairment reflects management’s current judgment regarding facts and circumstances specific to a security and the factors noted above. If that judgment changes, Ambac may ultimately record a charge for credit impairment in future periods. Ambac has made certain accounting policy elections related to accrued interest receivable ("AIR") for available-for-sale investments under CECL. Elections include: i) not measuring AIR for credit impairment, instead AIR is written off when it becomes 90 days past due; ii) writing off AIR by reversing interest income; iii) presenting AIR separately in Other Assets on the balance sheet and iv) excluding AIR from amortized cost balances in required CECL disclosures found in Note 4. Investments . AIR at December 31, 2023 and 2022 was $14 and $10, respectively. Refer to Note 4. Investments for further credit impairment disclosures. Premiums Legacy Financial Guarantee Insurance Gross premiums were received either upfront or in installments. For premiums received upfront, an unearned premium revenue (“UPR”) liability was established, which was initially recorded as the cash amount received. For installment premium transactions, a premium receivable asset and offsetting UPR liability was initially established in an amount equal to: (i) the present value of future contractual premiums due (the “contractual” method) or (ii) if the underlying insured obligation is a homogenous pool of assets which are contractually prepayable, the present value of premiums to be collected over the expected life of the transaction (the “expected” method). An appropriate risk-free rate corresponding to the weighted average life of each policy and currency is used to discount the future premiums contractually due or expected to be collected. For example, U.S. dollar exposures are discounted using U.S. Treasury rates while exposures denominated in a foreign currency are discounted using the appropriate risk-free rate for the respective currency. The weighted average risk-free rate at December 31, 2023 and 2022, was 3.2%. and 3.0%, respectively, and the weighted average period of future premiums used to estimate the premium receivable at December 31, 2023 and 2022, was 7.7 years and 8.0 years, respectively. Insured obligations consisting of homogeneous pools for which Ambac uses expected future premiums to estimate the premium receivable include residential mortgage-backed securities ("RMBS"). As prepayment assumptions change for homogenous pool transactions, or if there is an actual prepayment for a “contractual” method installment transaction, the related premium receivable and UPR are adjusted in equal and offsetting amounts with no immediate effect on earnings using new premium cash flows and the then current risk-free rate corresponding to the initial weighted average life of the related policy. For both upfront and installment premium policies, premium revenues are earned over the life of the financial guarantee contract in proportion to the insured principal amount outstanding at each reporting date (referred to as the level-yield method). For installment paying policies, the premium receivable discount, equating to the difference between the undiscounted future installment premiums and the present value of future installment premiums, is accreted as premiums earned in proportion to the premium receivable balance at each reporting date. When a bond issue insured by Ambac has been retired early, typically due to an issuer call, any remaining UPR is recognized at that time to the extent the financial guarantee contract is legally extinguished, causing accelerated premium revenue. For installment premium paying transactions, we offset the recognition of any remaining UPR by the reduction of the related premium receivable to zero (as it will not be collected as a result of the retirement), which may cause negative accelerated premium revenue. Certain obligations insured by Ambac have been legally defeased whereby government securities are purchased by the issuer with the proceeds of a new bond issuance, or less frequently with other funds of the issuer, and held in escrow. The principal and interest received from the escrowed securities are then used to retire the Ambac-insured obligations at a future date either to their maturity date (a refunding) or a specified call date (a pre-refunding). Ambac has evaluated the provisions in policies issued on these obligations and determined those insurance policies have not been legally extinguished. For policies with refunding securities, premium revenue recognition is not impacted as the escrowed maturity date is the same as the previous legal maturity date. For policies with pre-refunding securities, the maturity date of the pre-refunded security has been shortened from its previous legal maturity. Although premium revenue recognition has not been accelerated in the period of the pre-refunding, it results in an increase in the rate at which the policy's remaining UPR is to be recognized. For financial guarantee contracts, the issuer's ability and willingness to pay its insured debt obligation impacts the payment of policy losses by Ambac as well as the receipt of premiums from the issuer. As such, management leverages its existing loss reserve estimation process to evaluate credit impairment for premium receivables. Key factors in assessing credit impairment include historical premium collection data, internal risk classifications, credit ratings and loss severities. For structured finance transactions involving special purpose entities, we further evaluate the priority of premiums paid to Ambac within the contractual waterfall, as required by bond indentures. Ambac has a formal quarterly credit impairment review process for premium receivables. Management utilizes either a discounted cash flow ("DCF") or probability of default/loss given default ("PD/LGD") approach to estimate credit impairment on premium receivables. The DCF approach utilizes expected cash flows developed by Ambac's Risk Management Group using the same (or similar) models used for estimating loss reserves where such models can identify shortfalls in premiums. Credit impairment using the DCF approach is equal to the difference between amortized cost and the present value of expected cash flows. Credit impairment under the PD/LGD approach is the product of (i) the premium receivable carrying value, (ii) internally developed default probability (considering internal ratings and average life), and (iii) internally developed loss severities. Refer to Note 7. Insurance Contracts for further credit impairment disclosures. AAC has reinsurance in place pursuant to surplus share treaties and facultative reinsurance agreements. Similar to gross premiums, premiums ceded to reinsurers were paid either upfront or in installments. For premiums paid upfront, a deferred ceded premium asset was established which is initially recorded as the cash amount paid. For installment premiums, a ceded premiums payable liability and offsetting deferred ceded premium asset were initially established in an amount equal to: i) the present value of future contractual premiums due or ii) if the underlying insured obligation is a homogenous pool of assets, the present value of expected premiums to be paid over the life of the transaction. An appropriate risk-free rate corresponding to the weighted average life of each policy and exposure currency is used to discount the future premiums contractually due or expected to be collected. Premiums ceded to reinsurers reduce the amount of premiums earned by Ambac from its financial guarantee insurance policies. For both upfront and installment premiums, ceded premiums written are primarily recognized in earnings in proportion to and at the same time as the related gross premium revenue is recognized. For premiums paid to reinsurers on an installment basis, Ambac records the present value of future ceding commissions as an offset to ceded premiums payable, using the same assumptions noted above for installment premiums. Specialty Property and Casualty Insurance Gross written premiums on insurance policies are recorded at the inception of the policy and can be received on an upfront or installment basis. Ceded premiums written are based on contractual terms applied against related gross written premiums. Premiums, net of reinsurance, are recognized as revenue on a daily pro-rata basis over the term of the insured risk. Unearned premiums and Deferred ceded premiums represents the portion of gross and ceded premiums written that relate to unexpired risk, respectively. Premium receivables represent balances currently due and amounts not yet due from policyholders, insurance carriers, managing general agents or producers issuing insurance policies on Everspan's behalf. Premium receivables are reported net of an allowance for expected credit losses. The allowance is based upon Everspan's ongoing review of amounts outstanding, including delinquencies and write-offs, and other relevant factors. Credit risk is partially mitigated by the managing general agent's ability to cancel the policy on behalf of Everspan if the policyholder does not pay the premium, thereby reducing the related policy's premium written and Everspan's premium receivable. Loans Loans are reported at either their outstanding principal balance less unamortized discount or at fair value. • Loans not held by consolidated VIEs are reported at their outstanding principal balance less unamortized discount and are reported within Other assets on the Consolidated Balance Sheet. Interest income is earned using the effective interest method based upon interest accrued on the unpaid principal balance adjusted for accretion of discounts. A loan is considered impaired when, based on the financial condition of the borrower, it is probable that Ambac will be unable to collect all principal and interest due according to the contractual terms of the loan agreement. Ambac has a formal quarterly credit impairment review process for these loans. The key factors in assessing credit impairment are internal credit ratings and loss severities. Management utilizes a PD/LGD approach, similar to the one described above for financial guarantee premium receivables, which is applied to the loan carrying value. • Loans held by VIEs consolidated as required under the Consolidation Topic of the ASC are carried at fair value under the fair value option election with changes in fair value recorded in Income (loss) on variable interest entities on the Consolidated Statements of Total Comprehensive Income (Loss). Such loans are reported as Loans, at fair value within the Variable interest entity assets section of the Consolidated Balance Sheet. Derivative Contracts The Company has entered into derivative contracts primarily to hedge certain economic risks inherent in its asset and liability portfolios. None of Ambac’s derivative contracts were designated as hedges under the Derivatives and Hedging Topic of the ASC. Ambac's derivatives have consisted primarily of interest rate swaps and futures contracts. • Ambac's current derivatives portfolio consists of certain legacy interest rate swaps executed in connection with financial guarantee client financings. In recent years, Ambac's interest rate derivatives portfolio consisted primarily of interest rate swaps and futures contracts to economically hedge interest rate risk in the financial guarantee and investment portfolios, managed on the basis of its net sensitivity to changes in interest rates. The economic hedge positions of the portfolio were fully exited in early 2023. Changes in the fair value of these interest rate derivatives are recorded, along with changes in fair value of other derivative contracts, within Net gains (losses) on derivative contracts on the Consolidated Statements of Total Comprehensive Income (Loss). • VIEs consolidated under the Consolidation Topic of the ASC entered into derivative contracts to meet specified purposes within their securitization structure. Changes in fair value of consolidated VIE derivatives are included within Income (loss) on variable interest entities on the Consolidated Statements of Total Comprehensive Income (Loss). All derivatives are recorded on the Consolidated Balance Sheets at fair value on a gross basis; assets and liabilities are netted by counterparty only when a legal right of offset exists, and are included in Other assets and Other liabilities, respectively. Variation payments on centrally cleared swaps and futures contracts are considered settlements of the associated derivative balances and are reflected as a reduction to derivative liabilities or assets on the Consolidated Balance Sheets. For other derivatives, Ambac has determined that the amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral may not be used to offset amounts due under the derivative instruments in the normal course of settlement. Therefore, such amounts are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement and are included in Other assets on the Consolidated Balance Sheets. Refer to Note 9. Derivative Instruments for further discussion of the Company’s use of derivative instruments and their impact of the consolidated financial statements. Refer to Note 5. Fair Value Measurements for further description of the methodologies used to determine the fair value of derivative contracts, including model inputs and assumptions where applicable. Deferred Acquisition Costs, Ceding Commissions and Deferred Program Fees The Specialty Property and Casualty Program business defers acquisition costs incurred that are related directly to the successful acquisition of new or renewal insurance contracts, including commissions paid to managing general agents for direct business, and paid to insurance carriers when acquired via assumed reinsurance. Ceding commissions received from reinsurers represent a recovery of related acquisition costs. Deferred acquisition costs, net of ceding commissions, are amortized over the related policy period, generally one year, and recognized in amortization of deferred acquisition costs. Ceding commissions received in excess of the related direct acquisition costs are deferred and amortized over the related policy period, and recognized as program fees. Goodwill Goodwill is attributable to acquisitions in the Insurance Distribution segment and represents the acquisition cost in excess of the fair value of net assets acquired, including identifiable intangible assets. Goodwill is assigned at acquisition to the applicable reporting unit of the acquired entity giving rise to the goodwill. Goodwill is not amortized but is subject to impairment testing. Goodwill impairment tests are performed annually or more frequently if circumstances indicate a possible impairment. The annual test of goodwill impairment is as of October 1st of each year. Depending on the reporting unit, management utilizes one of two approaches for impairment testing. Under the first approach, qualitative factors are first assessed to determine if it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If it is more likely than not, then a quantitative impairment evaluation is performed. Under the second approach, management bypasses the qualitative evaluation and proceeds directly to the quantitative evaluation. The quantitative evaluation under both of the above approaches compares the estimated fair value of the reporting unit with its carrying value (including goodwill and identifiable intangible assets). An impairment is recognized for the excess of the carrying amount of the reporting unit over it estimated fair value. If the reporting unit’s estimated fair value exceeds its carrying value, goodwill is not impaired. There have been no accumulated impairment losses since this goodwill was established. Intangible Assets Financial Guarantee Insurance intangible: Upon Ambac's emergence from bankruptcy in 2013, an insurance intangible asset was recorded which represented the difference between the fair value and aggregate carrying value of the financial guarantee insurance and reinsurance assets and liabilities. The carrying values of financial guarantee insurance and reinsurance contracts continue to be reported and measured in accordance with their existing accounting policies. Pursuant to the Financial Services-Insurance Topic of the ASC, the insurance intangible is to be measured on a basis consistent with the related financial guarantee insurance and reinsurance contracts. The initial insurance intangible asset was assigned to groups of insurance and reinsurance contracts with similar characteristics and has been amortized using a level-yield method based on par exposure of the related groups. Finite-lived intangibles Ambac acquired identifiable intangible assets attributable to the Insurance Distribution segment. The intangible assets primarily relate to distribution relationships, non-compete agreements and trade names, all of which have finite lives and are amortized over their estimated useful lives using the straight-line method. The Company tests finite-lived acquired intangible assets for impairment if certain events occur or circumstances change indicating that the carrying amount of the intangible asset may not be recoverable. The carrying amount of the intangible asset is not recoverable if it exceeds the projected undiscounted cash flows expected to result from the use and eventual disposal of the asset or asset group. If deemed unrecoverable, an impairment loss is recognized for the excess carrying amount over the fair value. There have been no accumulated impairment losses since these finite-lived intangible assets were established. Indefinite-lived intangibles Ambac acquired identifiable intangible assets attributable to its acquisitions of carriers in both 2021 and 2022, which were accounted for as asset acquisitions (Specialty Property and Casualty Insurance segment). The intangible assets relate to insurance licenses which have indefinite lives and therefore are not amortized. The useful lives are re-evaluated each period to determine whether facts and circumstances continue to support an indefinite life. The Company tests indefinite-lived acquired intangible assets for impairment annually or more frequently if circumstances indicate a possible impairment. Ambac tests indefinite-lived intangibles for impairment as of October 1st of each year. If, after assessing qualitative factors, management believes it is more likely than not that the intangible assets are impaired, a quantitative impairment evaluation is performed. Management also has the option to bypass the qualitative evaluation and proceed directly to the quantitative evaluation. The quantitative test compares the estimated fair value of the intangible asset with its carrying value. An impairment is recognized for the excess of the carrying amount of the intangible asset over it estimated fair value. If the asset’s estimated fair value exceeds its carrying value, the intangible asset is not impaired. There have been no accumulated impairment losses since these indefinite-lived intangible assets were established. Restricted Cash Cash that we do not have the right to use for general purposes is recorded as restricted cash in our consolidated balance sheets. Restricted cash includes (i) consolidated variable interest entity cash restricted to support the obligations of the consolidated VIEs and (ii) fiduciary cash held by Ambac's insurance distribution subsidiaries as described below. Fiduciary Funds As an intermediary, we hold funds, generally in a fiduciary capacity, for the account of third parties, typically as the result of premiums received from retail brokers or insureds that are in transit to insurers and claims due that are in transit from insurers. Since fiduciary assets are not available for corporate use, they are shown in the consolidated balance sheets as restricted cash and we present an equal and corresponding fiduciary liability relating to these funds representing amounts or claims or premiums due on our consolidated balance sheets (included in Other liabilities). Fiduciary funds are generally required to be kept in bank accounts subject to guidelines which emphasize capital preservation and liquidity. The Company is entitled to retain investment income earned on certain of these fiduciary funds in accordance with industry custom and practice and, in some cases, as supported by agreements with insureds. Restricted cash for net uncollected premiums and claims and the related fiduciary liabilities were $12 and $14 at December 31, 2023 and 2022, respectively. Loss and Loss Adjustment Expenses Legacy Financial Guarantee The loss and loss adjustment expense reserve (“loss reserve”) policy relates only to Ambac’s non-derivative financial guarantee insurance business for insurance policies issued to beneficiaries, including VIEs, for which we do not consolidate the VIE. Losses and loss expenses are based upon estimates of the ultimate aggregate losses inherent in the insured portfolio as of the reporting date. The policy for derivative contracts is discussed in the “Derivative Contracts” section above. A loss reserve is recorded on the balance sheet on a policy-by-policy basis based upon the present value ("PV") of expected net claim cash outflows or expected net recovery cash inflows, discounted at risk-free rates. The estimate for future net cash flows consider the likelihood of al

Segment Reporting

Segment Reporting	12 Months Ended
Segment Reporting	Dec. 31, 2023
Segment Reporting [Abstract]
Segment Reporting Disclosure	3. SEGMENT INFORMATION The Company reports its results of operations in three segments: Legacy Financial Guarantee Insurance, Specialty Property and Casualty Insurance and Insurance Distribution, separate from Corporate and Other, which is consistent with the manner in which the Company's chief operating decision maker ("CODM") reviews the business to assess performance and allocate resources. See Note 1. Background and Business Description for a description of each of the Company's business segments.

Investments

Investments	12 Months Ended
Investments	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Investments	4. INVESTMENTS Ambac’s non-VIE invested assets are primarily comprised of (i) fixed maturity securities classified as either available-for-sale or trading securities, (ii) interests in pooled investment funds which are reported within Other investments on the Consolidated Balance Sheets and (iii) preferred equity investments which are reported within Other investments on the Consolidated Balance Sheets. Interests in pooled investment funds in the form of common stock or in-substance common stock are classified as trading securities, while limited partner interests in such funds are reported using the equity method. Fixed maturity securities classified as trading are unrated municipal bond and other obligations of Puerto Rico issuing entities received in connection with the 2022 restructuring of AAC-insured Puerto Rico obligations. Fixed Maturity Securities The amortized cost and estimated fair value of available-for-sale investments, excluding VIE investments, at December 31, 2023 and 2022 were as follows: December 31, 2023 December 31, 2022 Amortized Allowance for Credit Losses Gross Gross Estimated Amortized Allowance for Credit Losses Gross Gross Estimated Fixed maturity securities: Municipal obligations $ 72 $ — $ 1 $ 1 $ 72 $ 44 — — 2 43 Corporate obligations 785 — 4 44 745 659 — 1 63 598 Foreign obligations 105 — 1 6 100 85 — — 9 76 U.S. government obligations 85 — 1 4 82 68 — — 4 65 Residential mortgage-backed securities 239 3 28 14 250 230 — 28 19 238 Commercial mortgage-backed securities 19 — — — 19 15 — — — 15 Collateralized debt obligations 139 — 1 1 139 141 — — 4 137 Other asset-backed securities (1) 301 — 3 1 303 227 — 2 5 224 1,744 3 40 71 1,710 1,469 — 31 106 1,395 Short-term 426 — — — 426 507 — — — 507 2,170 3 40 71 2,135 1,977 — 31 106 1,902 Fixed maturity securities pledged as collateral: Short-term 27 — — — 27 64 — — — 64 27 — — — 27 64 — — — 64 Total available-for-sale investments $ 2,197 $ 3 $ 40 $ 71 $ 2,162 2,041 $ — $ 31 $ 106 $ 1,966 (1) Consists primarily of Ambac's holdings of military housing and student loan securities. The amortized cost and estimated fair value of available-for-sale investments, excluding VIE investments, at December 31, 2023, by contractual maturity, were as follows: Amortized Estimated Due in one year or less $ 544 $ 544 Due after one year through five years 581 560 Due after five years through ten years 293 271 Due after ten years 80 76 1,500 1,451 Residential mortgage-backed securities 239 250 Commercial mortgage-backed securities 19 19 Collateralized debt obligations 139 139 Other asset-backed securities 301 303 Total $ 2,197 $ 2,162 Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay certain obligations with or without call or prepayment penalties. Unrealized Losses on Fixed Maturity Securities The following table shows gross unrealized losses and fair values of Ambac’s available-for-sale investments, excluding VIE investments, which at December 31, 2023, did not have an allowance for credit losses under the CECL standard. This information is aggregated by investment category and length of time that the individual securities have been in a continuous unrealized loss position, at December 31, 2023 and 2022: December 31, 2023 December 31, 2022 Less Than 12 Months 12 Months or More Total Less Than 12 Months 12 Months or More Total Fair Gross Fair Value Gross Fair Value Gross Fair Gross Fair Value Gross Fair Value Gross Fixed maturity securities: Municipal obligations $ 7 $ — $ 16 $ 1 $ 23 $ 1 $ 21 $ 1 $ 7 $ 1 $ 28 $ 2 Corporate obligations 75 2 509 43 584 44 280 21 279 42 559 63 Foreign obligations 8 — 56 6 64 6 27 2 47 7 73 9 U.S. government obligations 27 1 37 2 63 4 40 3 19 1 58 4 Residential mortgage-backed securities 6 — 98 14 104 14 132 19 — — 132 19 Commercial mortgage-backed securities 3 — — — 3 — 3 — — — 3 — Collateralized debt obligations 1 — 93 1 95 1 90 3 36 1 126 4 Other asset-backed securities 57 1 35 1 92 1 198 4 5 1 203 5 184 4 844 68 1,028 71 791 53 392 53 1,183 106 Short-term 4 — — — 4 — 78 — 8 — 86 — Total temporarily impaired securities $ 187 $ 4 $ 844 $ 68 $ 1,032 $ 71 $ 869 $ 53 $ 400 $ 53 $ 1,269 $ 106 Management has determined that the securities in the above table do not have credit impairment as of December 31, 2023 and 2022 based upon (i) no actual or expected principal and interest payment defaults on these securities; (ii) analysis of the creditworthiness of the issuer and financial guarantor, as applicable, and (iii) for debt securities that are non-highly rated beneficial interests in securitized financial assets, analysis of whether there was an adverse change in projected cash flows. Management's evaluation as of December 31, 2023, includes the expectation that all principal and interest payments on securities guaranteed by AAC or Ambac UK will be made timely and in full. Ambac’s assessment about whether a security is credit impaired reflects management’s current judgment regarding facts and circumstances specific to the security and other factors. If that judgment changes, Ambac may record a charge for credit impairment in future periods. The declines in fair value and resultant unrealized losses across asset classes as of December 31, 2023, included in the above table resulted from the impact of increasing interest rates and market spreads. Management has determined that the securities with unrealized losses are not credit impaired. Further discussion of management's assessment with respect to security categories with larger unrealized loss balances is below. Corporate obligations The gross unrealized losses on corporate obligations as of December 31, 2023, resulted from an increase in interest rates and, to a lesser extent, market spreads since the securities were purchased. Unrealized losses of $44 related to 662 investment grade securities with an average unrealized loss equal to 7% of amortized cost at December 31, 2023. Securities that have below investment grade credit ratings or are unrated comprise $1 of the gross unrealized loss and have an average unrealized loss equal to 5% of amortized cost at December 31, 2023. Management believes that the full and timely receipt of all principal and interest payment on corporate obligations with unrealized losses as of December 31, 2023, is probable. Residential mortgage-backed securities As of December 31, 2023, all of the $14 unrealized loss on residential mortgage-backed securities related to 11 Ambac-insured securities. Four of these account for $13 of the unrealized loss and have an average unrealized loss equal to 14% of amortized cost. The majority of these unrealized losses relate to securities with long dated weighted average lives making their fair values more sensitive to interest rate changes. Also, most of these securities have below investment grade credit ratings or are unrated. The unrealized losses on these obligations resulted from adverse market conditions for long dated credit assets. As noted above, expected cash flows used in evaluating credit impairment of Ambac-insured securities contemplate full and timely payment of all principal and interest payments on Ambac-insured securities. This assumption is included in the projection of model based cash flows used in evaluating credit impairments on beneficial interests in securitized financial assets, including the residential mortgage backed and student loan asset backed securities included in this group. Investment Income (Loss) Net investment income (loss) was comprised of the following for the affected periods: Year Ended December 31, 2023 2022 2021 Fixed maturity securities $ 76 $ 61 $ 78 Short-term investments 22 11 — Loans — 1 — Investment expense (6) (6) (6) Securities available-for-sale and short-term 93 66 74 Fixed maturity securities - trading 7 (23) — Other investments 40 (26) 66 Total net investment income (loss) $ 140 $ 17 $ 139 Net investment income (loss) from Other investments primarily represents changes in fair value on equity securities including certain pooled investment funds, and income from investment limited partnerships and other equity interests accounted for under the equity method. Net Investments Gains (Losses), including Impairments The following table details amounts included in net investment gains (losses) and impairments included in earnings for the affected periods: Year Ended December 31, 2023 2022 2021 Gross realized gains on securities $ 1 $ 36 $ 14 Gross realized losses on securities (4) (18) (2) Foreign exchange (losses) gains (4) 14 (5) Credit impairments (3) — — Intent to sell impairments (12) — — Net investment gains (losses), including impairments $ (22) $ 31 $ 7 Ambac had an allowance for credit losses $3 and $0 at December 31, 2023 and 2022, respectively. The increase of $3 for the year ended December 31, 2023 relates to additions to the allowance for credit losses on residential mortgage-backed securities for which credit losses were not previously recorded. Ambac did not purchase any financial assets with credit deterioration for the years ended December 31, 2023 and 2022. Counterparty Collateral, Deposits with Regulators and Other Restrictions Ambac routinely pledges and receives collateral related to certain transactions. Securities held directly in Ambac’s investment portfolio with a fair value of $27 and $64 at December 31, 2023 and 2022, respectively, were pledged to derivative counterparties. Ambac’s derivative counterparties have the right to re-pledge the investment securities and as such, these pledged securities are separately classified on the Consolidated Balance Sheets as "Short-term investments pledged as collateral, at fair value". Refer to Note 9. Derivative Instruments for further information on cash collateral. There was no cash or securities received from other counterparties that were re-pledged by Ambac. Securities carried at $24 and $23 at December 31, 2023 and 2022, respectively, were deposited by Ambac's insurance subsidiaries with governmental authorities or designated custodian banks as required by laws affecting insurance companies. Invested assets carried at $1 as December 31, 2023, were deposited as security in connection with a letter of credit issued for an office lease. Fiduciary funds held by Ambac's insurance distribution subsidiaries, carried at $2 and $— at December 31, 2023 and 2022, respectively, are included in invested assets. Guaranteed Securities Ambac’s fixed maturity portfolio includes securities covered by guarantees issued by AAC or Ambac UK (“insured securities”). The following table represents the fair value and weighted-average underlying rating of insured securities in Ambac's investment portfolio at December 31, 2023 and 2022, respectively: December 31, Municipal Mortgage-backed Securities Asset-backed Securities Total Weighted (1) 2023: $ 9 $ 240 $ 232 $ 482 B- 2022: $ 10 $ 236 $ 157 $ 403 B (1) Ratings are based on the lower of Standard & Poor’s or Moody’s rating. If unavailable, Ambac’s internal rating is used. Other Investments Ambac's investment portfolio includes interests in various pooled investment funds. Fair value and additional information about investments in pooled funds, by investment type, is summarized in the table below. Except as noted in the table, fair value as reported is determined using net asset value ("NAV") as a practical expedient. Redemption of certain funds valued using NAV may be subject to withdrawal limitations and/or redemption fees which vary with the timing and notification of withdrawal provided by the investor. In addition to these investments, Ambac has unfunded commitments of $41 to private credit and private equity funds at December 31, 2023. Class of Funds 2023 2022 Redemption Frequency Redemption Notice Period Hedge funds (1) $ 112 $ 186 quarterly or semi-annually 90 days High yield and leveraged loans (2) (10) 85 80 daily 0 - 30 days Private credit (3) 84 84 quarterly if permitted 180 days if permitted Private equity (4) 70 47 quarterly if permitted 90 days if permitted Investment grade floating rate income (5) 52 63 weekly 0 days Equity market investments (6) (10) 38 64 daily or quarterly 0 - 90 days Real estate properties (7) 21 22 see footnote (7) see footnote (7) Insurance-linked investments (8) 1 1 see footnote (9) see footnote (9) Convertible bonds (9)(10) — 8 daily 0 days Total equity investments in pooled funds $ 463 $ 556 (1) This class seeks to generate superior risk-adjusted returns through selective asset sourcing, active trading and hedging strategies across a range of asset types. (2) This class of funds includes investments in high quality floating rate debt securities including ABS and corporate floating rate notes. (3) This class aims to obtain high long-term returns primarily through credit and preferred equity investments with low liquidity and defined term. (4) This class seeks to generate long-term capital appreciation through investments in private equity, equity-related and other instruments. (5) This class of funds includes investments in high quality floating rate debt securities including ABS and corporate floating rate notes. (6) This class of funds aim to achieve long-term growth through diversified exposure to global equity markets. (7) Investments consist of UK property to generate income and capital growth. (8) This class seeks to generate returns from insurance markets through investments in catastrophe bonds, life insurance and other insurance linked investments. This investment is restricted in connection with the unwind of certain insurance linked exposures. Ambac has redeemed its investment to the extent permitted by the fund. (9) This class seeks to generate total return from portfolios focused primarily on convertible securities. (10) These categories include fair value amounts totaling $77 and $61 at December 31, 2023 and 2022, respectively, that are readily determinable and are priced through pricing vendors, including for Equity market investments of $38 and $53, High yield and leveraged loans products $39 and $0, and Convertible bonds investments $0 and $8. Other investments also includes preferred equity investments with a carrying value of $13 and $12 as of December 31, 2023 and 2022, respectively, that do not have readily determinable fair values and are carried at cost, less any impairments as permitted under the Investments — Equity Securities Topic of the ASC. There were no impairments recorded on these investments or adjustments to fair value to reflect observable price changes in identical or similar investments from the same issuer during the periods presented. The portion of net unrealized gains (losses) related to securities classified as trading and equity securities, excluding those reported using the equity method, still held at the end of each period is as follows: Year Ended December 31, 2023 2022 2021 Net gains (losses) recognized during the period on trading and equity securities $ 25 $ (48) $ 23 Less: net gains (losses) recognized during the reporting period on trading and equity securities sold during the period 18 (26) 1 Unrealized gains (losses) recognized during the reporting period on trading and equity securities still held at the reporting date $ 7 $ (22) $ 22
Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities	The following table represents the fair value and weighted-average underlying rating of insured securities in Ambac's investment portfolio at December 31, 2023 and 2022, respectively: December 31, Municipal Mortgage-backed Securities Asset-backed Securities Total Weighted (1) 2023: $ 9 $ 240 $ 232 $ 482 B- 2022: $ 10 $ 236 $ 157 $ 403 B (1) Ratings are based on the lower of Standard & Poor’s or Moody’s rating. If unavailable, Ambac’s internal rating is used.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	5. FAIR VALUE MEASUREMENTS The Fair Value Measurement Topic of the ASC establishes a framework for measuring fair value and disclosures about fair value measurements. Fair Value Hierarchy The Fair Value Measurement Topic of the ASC specifies a fair value hierarchy based on whether the inputs to valuation techniques used to measure fair value are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect Company-based assumptions. The fair value hierarchy has three broad levels as follows: l Level 1 Quoted prices for identical instruments in active markets. Assets and liabilities classified as Level 1 include US Treasury and other foreign government obligations traded in highly liquid and transparent markets, certain highly liquid pooled fund investments, exchange traded futures contracts and money market funds. l Level 2 Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets. Assets and liabilities classified as Level 2 generally include investments in fixed maturity securities representing municipal, asset-backed and corporate obligations, certain interest rate swap contracts and most long-term debt of variable interest entities consolidated under the Consolidation Topic of the ASC. l Level 3 Model derived valuations in which one or more significant inputs or significant value drivers are unobservable. This hierarchy requires the use of observable market data when available. Assets and liabilities classified as Level 3 include certain uncollateralized interest rate swap contracts and certain investments in fixed maturity securities. Additionally, Level 3 assets and liabilities generally include loan receivables, and certain long-term debt of variable interest entities consolidated under the Consolidation Topic of the ASC. The Fair Value Measurement Topic of the ASC permits, as a practical expedient, the estimation of fair value of certain investments in funds using the net asset value per share of the investment or its equivalent (“NAV”). Investments in funds valued using NAV are not categorized as Level 1, 2 or 3 under the fair value hierarchy. The Investments — Equity Securities Topic of the ASC permits the measurement of certain equity securities without a readily determinable fair value at cost, less impairment, and adjusted to fair value when observable price changes in identical or similar investments from the same issuer occur (the "measurement alternative"). The fair values of investments measured under this measurement alternative are not included in the below disclosures of fair value of financial instruments. The following table sets forth the carrying amount and fair value of Ambac’s financial assets and liabilities as of December 31, 2023 and 2022, including the level within the fair value hierarchy at which fair value measurements are categorized. As required by the Fair Value Measurement Topic of the ASC financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. December 31, 2023: December 31, 2022: Carrying Total Fair Fair Value Measurements Categorized as: Carrying Total Fair Fair Value Measurements Categorized as: Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Financial assets: Fixed maturity securities: Municipal obligations $ 99 $ 99 $ — $ 99 $ — $ 102 $ 102 $ — $ 102 $ — Corporate obligations 745 745 — 726 19 598 598 — 585 12 Foreign obligations 100 100 100 — — 76 76 76 — — U.S. government obligations 82 82 82 — — 65 65 65 — — Residential mortgage-backed securities 250 250 — 250 — 238 238 — 238 — Commercial mortgage-backed securities 19 19 — 19 — 15 15 — 15 — Collateralized debt obligations 139 139 — 139 — 137 137 — 137 — Other asset-backed securities 303 303 — 235 68 224 224 — 157 67 Fixed maturity securities, pledged as collateral: Short-term 27 27 27 — — 64 64 64 — — Short term investments 426 426 421 5 — 507 507 506 1 — Other investments (1) 475 463 77 — — 568 556 61 — — Cash, cash equivalents and restricted cash 28 28 27 2 — 44 44 43 1 — Other assets - Derivatives: Interest rate swaps—asset position 25 25 — — 25 27 27 — 1 26 Warrants 1 1 — — 1 1 1 — — 1 Other assets-loans 2 2 — — 2 10 10 — — 10 Variable interest entity assets: Fixed maturity securities: Corporate obligations, fair value option 2,072 2,072 — — 2,072 1,828 1,828 — — 1,828 Fixed maturity securities: Municipal obligation, trading — — — — — 43 43 — 43 — Fixed maturity securities: Municipal obligations, available-for-sale 95 95 — 95 — 96 96 — 96 — Restricted cash 246 246 246 — 17 17 17 — — Loans 1,663 1,663 — — 1,663 1,829 1,829 — — 1,829 Derivative assets: Interest rate swaps—asset position 190 190 — 190 — 190 190 — 190 — Derivative assets: Currency swaps—asset position 36 36 — 36 — 49 49 — 49 — Total financial assets $ 7,022 $ 7,010 $ 979 $ 1,795 $ 3,850 $ 6,726 $ 6,715 $ 833 $ 1,615 $ 3,772 Financial liabilities: Long term debt, including accrued interest $ 983 $ 697 $ — $ 679 $ 18 $ 1,065 $ 878 $ — $ 864 $ 14 Other liabilities - Derivatives: Interest rate swaps—liability position 35 35 — 35 — 38 38 — 38 — Liabilities for net financial guarantees written (2) 292 788 — — 788 159 476 — — 476 Variable interest entity liabilities: Long-term debt (includes $2,710 and $2,788 at fair value) 2,967 2,980 — 2,760 220 3,107 3,145 — 2,992 154 Derivative liabilities: Interest rate swaps—liability position 1,197 1,197 — 1,197 — 1,048 1,048 — 1,048 — Total financial liabilities $ 5,474 $ 5,697 $ — $ 4,671 $ 1,026 $ 5,418 $ 5,586 — 4,942 644 (1) Excluded from the fair value measurement categories in the table above are investment funds of $386 and $494 as of December 31, 2023 and 2022, respectively, which are measured using NAV as a practical expedient. Also excluded from the fair value measurements in the table above are equity securities with a carrying value of $13 and $12 as of December 31, 2023 and 2022, respectively, that do not have readily determinable fair values and have carrying amounts determined using the measurement alternative. (2) The carrying value of net financial guarantees written includes financial guarantee amounts in the following balance sheet items: Premium receivables; Reinsurance recoverable on paid and unpaid losses; Deferred ceded premium; Subrogation recoverable; Insurance intangible asset; Unearned premiums; Loss and loss adjustment expense reserves; Ceded premiums payable, premiums taxes payable and other deferred fees recorded in Other liabilities. Determination of Fair Value When available, Ambac uses quoted active market prices specific to the financial instrument to determine fair value and classifies such items within Level 1. The determination of fair value for financial instruments categorized in Level 2 or 3 involves judgment due to the complexity of factors contributing to the valuation. Third-party sources from which we obtain independent market quotes also use assumptions, judgments and estimates in determining financial instrument values and different third parties may use different methodologies or provide different values for financial instruments. In addition, the use of internal valuation models may require assumptions about hypothetical or inactive markets. As a result of these factors, the actual trade value of a financial instrument in the market, or exit value of a financial instrument position by Ambac, may be significantly different from its recorded fair value. Ambac’s financial instruments carried at fair value are mainly comprised of investments in fixed maturity securities, equity interests in pooled investment funds, derivative instruments, and certain variable interest entity assets and liabilities. Valuation of financial instruments is performed by Ambac’s finance group using methods approved by senior financial management with consultation from risk management and portfolio managers as appropriate. Preliminary valuation results are discussed with portfolio managers quarterly to assess consistency with market transactions and trends as applicable. Market transactions such as trades or negotiated settlements of similar positions, if any, are reviewed to validate fair value model results. However many of the financial instruments valued using significant unobservable inputs have very little or no observable market activity. Methods and significant inputs and assumptions used to determine fair values across portfolios are reviewed quarterly by senior financial management. Other valuation control procedures specific to particular portfolios are described further below. Fixed Maturity Securities The fair values of fixed maturity investment securities are based primarily on market prices received from broker quotes or alternative pricing sources. Because many fixed maturity securities do not trade on a daily basis, pricing sources apply available market information through processes such as matrix pricing to calculate fair value. Such prices generally consider a variety of factors, including recent trades of the same and similar securities. In those cases, the items are classified within Level 2. For those fixed maturity investments where quotes were not available or cannot be reasonably corroborated, fair values are based on internal valuation models. Key inputs to the internal valuation models generally include maturity date, coupon and yield curves for asset-type and credit rating characteristics that closely match those characteristics of the specific investment securities being valued. Items valued using valuation models are classified according to the lowest level input or value driver that is significant to the valuation. Thus, an item may be classified in Level 3 even though there may be significant inputs that are readily observable. Longer (shorter) expected maturities or higher (lower) yields used in the valuation model will, in isolation, result in decreases (increases) in fair value. Generally, lower credit ratings or longer expected maturities will be accompanied by higher yields used to value a security. At December 31, 2023, approximately 2%, 94%, and 4% of the fixed maturity investment portfolio (excluding variable interest entity investments) was valued using broker quotes, alternative pricing sources and internal valuation models, respectively. At December 31, 2022, approximately 5%, 91%, and 4% of the fixed maturity investment portfolio (excluding variable interest entity investments) was valued using broker quotes, alternative pricing sources and internal valuation models, respectively. Ambac performs various review and validation procedures to quoted and modeled prices for fixed maturity securities, including price variance analyses, missing and static price reviews, overall valuation analysis by portfolio managers and finance managers and reviews associated with our ongoing impairment analysis. Unusual prices identified through these procedures will be evaluated further against alternative third-party quotes (if available), internally modeled prices and/or other relevant data, and the pricing source values will be challenged as necessary. Price challenges generally result in the use of the pricing source’s quote as originally provided or as revised by the source following their internal diligence process. A price challenge may result in a determination by either the pricing source or Ambac management that the pricing source cannot provide a reasonable value for a security or cannot adequately support a quote, in which case Ambac would resort to using either other quotes or internal models. Results of price challenges are reviewed by portfolio managers and finance managers. Information about the valuation inputs for fixed maturity securities classified as Level 3 is included below: Other asset-backed securities: This security is a subordinated tranche of a securitization collateralized by Ambac-insured military housing bonds. The fair value classified as Level 3 was $68 and $67 at December 31, 2023 and 2022, respectively. Fair value was calculated using a discounted cash flow approach with expected future cash flows discounted using a yield consistent with the security type and rating. Significant inputs for the valuation at December 31, 2023 and 2022 include the following: December 31, 2023 2022 a. Coupon rate 5.97% 5.98% b. Average Life 12.80 years 13.46 years c. Yield 12.00% 12.60% Corporate obligations: This includes certain investments in convertible debt securities. The fair value classified as Level 3 was $19 and $12 at December 31, 2023 and 2022, respectively. Fair value was calculated by discounting cash flows to average maturity of 0.89 years and yield of 11.2% at December 31, 2023, and 1.75 years and a yield of 11.3% at December 31, 2022. Yields used are consistent with the security type and rating. Other Investments Other investments primarily relate to investments in pooled investment funds. The fair value of pooled investment funds is determined using dealer quotes or alternative pricing sources when such investments have readily determinable fair values. When fair value is not readily determinable, pooled investment funds are valued using NAV as a practical expedient as permitted under the Fair Value Measurement Topic of the ASC. Refer to Note 4. Investments for additional information about such investments in pooled funds that are reported at fair value using NAV as a practical expedient. Derivative Instruments Ambac’s derivative instruments primarily comprise interest rate swaps and exchange traded futures contracts. Fair value is determined based upon market quotes from independent sources, when available. When independent quotes are not available, fair value is determined using valuation models. These valuation models require market-driven inputs, including contractual terms, credit spreads and yield curves. The valuation of certain derivative contracts also require the use of data inputs and assumptions that are determined by management and are not readily observable in the market. Under the Fair Value Measurement Topic of the ASC, Ambac is required to consider its own credit risk when measuring the fair value of derivative liabilities. Factors considered in estimating the amount of any Ambac credit valuation adjustment ("CVA") on such contracts include collateral posting provisions, right of set-off with the counterparty, the period of time remaining on the derivative and the pricing of recent terminations. The aggregate Ambac CVA impact was not significant to the fair value of derivatives at both December 31, 2023 or 2022. Interest rate swaps that are not centrally cleared are valued using vendor-developed models that incorporate interest rates and yield curves that are observable and regularly quoted. These models provide the net present value of the derivatives based on contractual terms and observable market data. Generally, the need for counterparty (or Ambac) CVAs on interest rate derivatives is mitigated by the existence of collateral posting agreements under which adequate collateral has been posted. Certain of these derivative contracts entered into with financial guarantee customers are not subject to collateral posting agreements. Counterparty credit risk related to such customer derivative assets is included in our determination of their fair value. As of December 31, 2023 Ambac holds warrants to purchase preferred stock of a development stage company. These warrants have a fair value of $1 as of December 31, 2023, determined using a standard warrant valuation model with internally developed input assumptions. Financial Guarantees Fair value of net financial guarantees written represents our estimate of the cost to Ambac to completely transfer its insurance obligation to another market participant of comparable credit worthiness. In theory, this amount should be the same amount that another market participant of comparable credit worthiness would hypothetically charge in the marketplace, on a present value basis, to provide the same protection as of the balance sheet date. This fair value estimate of financial guarantees is presented on a net basis and includes direct and assumed contracts written, net of ceded reinsurance contracts. Long-term Debt As of December 31, 2023, long-term debt includes AAC surplus notes and the Ambac UK debt issued in connection with a policy commutation. As further described in Note 12. Long-term Debt the Tier 2 Notes were fully redeemed effective January 15, 2023. The fair values of surplus notes and Tier 2 Notes are classified as Level 2. The fair value of Ambac UK debt is classified as Level 3. Other Financial Assets and Liabilities Included in Other assets are loans, the fair values of which are estimated based upon internal valuation models and are classified as Level 3. Variable Interest Entity Assets and Liabilities The financial assets and liabilities of Legacy Financial Guarantee Insurance VIEs ("LFG VIEs") consolidated under the Consolidation Topic of the ASC consist primarily of fixed maturity securities and loans held by the VIEs, derivative instruments and notes issued by the VIEs which are reported as long-term debt. As described in Note 11. Variable Interest Entities, these LFG VIEs are securitization entities which have liabilities and/or assets guaranteed by AAC or Ambac UK. The fair values of LFG VIE long-term debt are based on price quotes received from independent market sources when available. Such quotes are considered Level 2 and generally consider a variety of factors, including recent trades of the same and similar securities. For those instruments where quotes were not available or cannot be reasonably corroborated, fair values are based on internal valuation models and classified Level 3. Comparable to the sensitivities of investments in fixed maturity securities described above, longer (shorter) expected maturities or higher (lower) yields used in the valuation model will, in isolation, result in decreases (increases) in fair value liability measurement for LFG VIE long-term debt. LFG VIE derivative asset and liability fair values are determined using vendor-developed valuation models, which incorporated observable market data related to specific derivative contractual terms including interest rates, foreign exchange rates and yield curves. The fair value of LFG VIE fixed maturity securities and loan assets are generally based on Level 2 market price quotes received from independent market sources when available. When LFG VIE asset fair values are not readily available from market quotes, values are estimated internally and classified Level 3. Internal valuations of LFG VIE’s fixed maturity securities or loan assets are derived from the fair values of the notes issued by the respective VIE and the VIE’s derivatives, determined as described above, adjusted for the fair values of Ambac’s financial guarantees associated with the VIE. The fair value of financial guarantees consist of: (i) estimated future premium cash flows discounted at a rate consistent with that implicit in the fair value of the VIE’s liabilities and (ii) estimates of future claim payments discounted at a rate that includes Ambac’s own credit risk. Estimated future premium payments to be paid by the VIEs were discounted at a weighted average rate of 6.3% and 6.8% at December 31, 2023 and 2022, respectively. At December 31, 2023, the range of these discount rates was between 5.3% and 7.8%. At December 31, 2022, the range of these discount rates was between 5.8% and 8.5%. Additional Fair Value Information for Financial Assets and Liabilities Accounted for at Fair Value The following tables present the changes in the Level 3 fair value category for the periods presented in 2023, 2022 and 2021. Ambac classifies financial instruments in Level 3 of the fair value hierarchy when there is reliance on at least one significant unobservable input to the valuation model. In addition to these unobservable inputs, the valuation models for Level 3 financial instruments typically also rely on a number of inputs that are readily observable either directly or indirectly. Thus, the gains and losses presented below include changes in the fair value related to both observable and unobservable inputs. Level-3 Financial Assets and Liabilities Accounted for at Fair Value VIE Assets and Liabilities Year ended December 31, 2023 Investments Derivatives Investments Loans Total Balance, beginning of period $ 79 $ 26 $ 1,828 $ 1,829 $ 3,762 Total gains/(losses) realized and unrealized: Included in earnings 1 — 200 142 343 Included in other comprehensive income 3 — 68 100 170 Purchases 6 — — — 6 Issuances — — — — — Sales — — — — — Settlements (2) — (24) (274) (300) Balance, end of period $ 87 $ 26 $ 2,072 $ 1,663 $ 3,848 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 1 $ — $ 200 $ 142 $ 343 The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 3 $ — $ 68 $ 100 $ 170 Level-3 Financial Assets and Liabilities Accounted for at Fair Value VIE Assets and Liabilities Year Ended December 31, 2022 Investments Derivatives Investments Loans Total Balance, beginning of period $ 91 $ 70 $ 3,320 $ 2,718 $ 6,199 Total gains/(losses) realized and unrealized: Included in earnings 1 (38) (789) (333) (1,160) Included in other comprehensive income (12) — (353) (279) (644) Purchases — — — — — Issuances — — — — — Sales — — — — — Settlements (1) (6) (349) (278) (633) Balance, end of period $ 79 $ 26 $ 1,828 $ 1,829 $ 3,762 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 1 $ (38) $ (789) $ (333) $ (1,160) The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ (12) $ — $ (353) $ (279) $ (644) Level-3 Financial Assets and Liabilities Accounted for at Fair Value Other Assets VIE Assets and Liabilities Year Ended December 31, 2021 Investments Derivatives Investments Loans Total Balance, beginning of period $ 78 $ 1 $ 84 $ 3,215 $ 2,998 $ 6,376 Total gains/(losses) realized and unrealized: Included in earnings 1 — (6) 176 59 230 Included in other comprehensive income 1 — — (32) (26) (58) Purchases 13 — — — — 13 Issuances — — — — — — Sales — — — — — — Settlements (2) (1) (8) (38) (313) (362) Balance, end of period $ 91 $ — $ 70 $ 3,320 $ 2,718 $ 6,199 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ (1) $ — $ (6) $ 176 $ 59 $ 227 The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ (1) $ — $ — $ (32) $ (26) $ (59) Invested assets and VIE long-term debt are transferred into Level 3 when internal valuation models that include significant unobservable inputs are used to estimate fair value. All such securities that have internally modeled fair values have been classified as Level 3. Derivative instruments are transferred into Level 3 when the use of unobservable inputs becomes significant to the overall valuation. There were no transfers of financial instruments into or out of Level 3 in the periods disclosed. Gains and losses (realized and unrealized) relating to Level 3 assets and liabilities included in earnings for the affected periods are reported as follows: Net Net Gains Income (Loss) Other Year Ended December 31, 2023 Total gains (losses) included in earnings for the period $ 1 $ — $ 341 $ — Changes in unrealized gains (losses) relating to financial instruments still held at the reporting date — — 341 — Year Ended December 31, 2022 Total gains (losses) included in earnings for the period $ 1 $ (38) $ (1,123) $ — Changes in unrealized gains (losses) relating to financial instruments still held at the reporting date 1 (39) (1,123) — Year Ended December 31, 2021 Total gains (losses) included in earnings for the period $ 1 $ (6) $ 235 $ — Changes in unrealized gains (losses) relating to financial instruments still held at the reporting date 1 (6) 235 —

Financial Guarantees in Force (

Financial Guarantees in Force (Notes)	12 Months Ended
Financial Guarantees in Force (Notes)	Dec. 31, 2023
Guarantees [Abstract]
Financial Guarantees in Force	6. FINANCIAL GUARANTEES IN FORCE Legacy financial guarantees outstanding includes the exposures of policies that insure variable interest entities (“VIEs”) consolidated in accordance with ASC Topic 810, Consolidation. Financial guarantees outstanding include the exposure of policies that insure capital appreciation bonds which are reported at the par amount at the time of issuance of the insurance policy as opposed to the current accreted value of the bonds. Financial guarantees outstanding exclude the exposures of policies that insure bonds which have been refunded, pre-refunded or synthetically commuted. The gross par amount of financial guarantees outstanding was $26,005 and $27,551 at December 31, 2023 and 2022, respectively. The par amount of financial guarantees outstanding, net of reinsurance, was $19,541 and $22,613 at December 31, 2023 and 2022, respectively. As of December 31, 2023, the aggregate amount of financial guarantee insured par ceded to reinsurers under reinsurance agreements was $6,464 with the largest reinsurer accounting for $2,766 or 10.6% of gross par outstanding at December 31, 2023. As of December 31, 2023 and 2022, the legacy financial guarantee portfolio consisted of the types of guaranteed bonds as shown in the following table: Net Par Outstanding December 31, (1) 2023 2022 Public Finance: Housing revenue (2) $ 3,443 $ 5,491 Lease and tax-backed revenue 1,542 1,979 General obligation 1,051 1,301 Other 1,526 1,776 Total Public Finance 7,562 10,547 Structured Finance: Mortgage-backed and home equity 1,712 1,930 Investor-owned utilities 1,077 1,103 Other 526 579 Total Structured Finance 3,315 3,612 International Finance: Sovereign/sub-sovereign 4,221 4,077 Investor-owned and public utilities 2,855 2,583 Asset-backed and other 862 1,083 Transportation 726 711 Total International Finance 8,664 8,454 Total $ 19,541 $ 22,613 (1) Net Par Outstanding includes capital appreciation bonds, which are reported at the par amount at the time of issuance of the insurance policy as opposed to the current accreted value of the bond. (2) Includes $3,371 and $5,400 of Military Housing net par at December 31, 2023 and 2022, respectively. As of December 31, 2023 and 2022, the financial guaranteed portfolio by location of risk was as outlined in the table below: Net Par Outstanding December 31, 2023 2022 United States $ 10,877 $ 14,159 United Kingdom 7,502 7,223 Italy 576 644 Austria 307 310 Australia 266 259 France 12 14 Other international 1 4 Total $ 19,541 $ 22,613 Gross financial guarantees in force (principal and interest) were $41,733 and $44,734 at December 31, 2023 and 2022, respectively. Net financial guarantees in force (after giving effect to reinsurance) were $29,121 and $34,975 as of December 31, 2023 and 2022, respectively. In the United States, no state accounted for more than 6% of the total net par outstanding at December 31, 2023. The highest single insured risk represented 4.6% of the total net par amount guaranteed.

Financial Guarantee Insurance C

Financial Guarantee Insurance Contracts	12 Months Ended
Financial Guarantee Insurance Contracts	Dec. 31, 2023
Insurance [Abstract]
Reinsurance	Reinsurance Recoverables, Including Credit Impairments: Ambac’s reinsurance assets, including deferred ceded premiums and reinsurance recoverables on losses amounted to $398 at December 31, 2023. Credit exposure existed at December 31, 2023, with respect to reinsurance recoverables to the extent that any reinsurer may not be able to reimburse Ambac under the terms of these reinsurance arrangements. At December 31, 2023, there were ceded reinsurance balances payable of $90 offsetting this credit exposure. Contractually ceded reinsurance payables can only be offset against amounts owed from the same reinsurer in the event that such reinsurer is unable to meet its obligations to reimburse Ambac. To minimize its credit exposure to losses from reinsurer insolvencies, Ambac (i) is entitled to receive collateral from its reinsurance counterparties in certain reinsurance contracts and (ii) has certain cancellation rights that can be exercised by Ambac in the event of rating agency downgrades of a reinsurer (among other events and circumstances). Ambac held letters of credit and collateral amounting to $131 from its reinsurers at December 31, 2023. For those reinsurance counterparties that do not currently post collateral, Ambac's reinsurers are well capitalized, highly rated, authorized capacity providers. Additionally, while legacy liabilities from the Providence Washington Insurance Company ("PWIC") acquisition and the three admitted carriers acquired by Everspan on January 3, 2022 (the "21st Century Companies") were fully ceded to certain reinsurers, Everspan also benefits from an unlimited, uncapped indemnity from Enstar Holdings (US) and 21st Century Premier Insurance Company, respectively, to mitigate any residual risk to these reinsurers. For 2023, our top three reinsurers represented 74% our total reinsurance recoverables on paid and unpaid losses. These reinsurance recoverables were primarily from reinsurers with applicable ratings of A or better. The following table sets forth our three most significant reinsurers by amount of reinsurance recoverable as of December 31, 2023. Reinsurers Type of Insurance Rating (1) Reinsurance Recoverable (2) Unsecured Recoverable (3) General Reinsurance Company Specialty P&C A++ $ 81 $ 69 QBE Insurance Corporation Specialty P&C A 38 38 Assured Guaranty Re Ltd. Financial AA 25 — All other reinsurers 50 21 Total recoverables $ 195 $ 128 (1) Represents financial strength ratings from S&P for financial guarantee reinsurers and AM Best for specialty P&C reinsurers. (2) Represents reinsurance recoverables on paid and unpaid losses. Unsecured amounts from QBE Insurance Corporation is also supported by an unlimited, uncapped indemnity from Enstar Holdings (US). (3) Reinsurance recoverables reduced by ceded premiums payables due to reinsurers, letters of credit, and collateral posted for the benefit of Ambac. Ambac has uncollateralized credit exposure to reinsurers of $128 and $60 and has recorded an allowance for credit losses of less than a million at December 31, 2023 and December 31, 2022, respectively. The uncollateralized credit exposure to reinsurers includes legacy liabilities obtained from the acquisitions of PWIC and the 21st Century Companies of $44 and $45 at December 31, 2023 and December 31, 2022, respectively. All legacy liabilities remain with affiliates of the sellers through reinsurance and contractual indemnities.
Liability for Future Policy Benefits and Unpaid Claims Disclosure	The following is a summary of loss and loss adjustment expense reserves, including certain components, for the Company’s major product lines by reporting segment at December 31, 2023. Net Loss and Loss Adjustment Expense Reserves Reinsurance Recoverables on Unpaid Losses Loss and Loss Adjustment Reserves Commercial auto $ 22 $ 85 $ 107 Unallocated loss adjustment expense reserves 5 2 6 Other (1) 14 69 84 Total 41 156 197

Insurance Regulatory Restrictio

Insurance Regulatory Restrictions (Notes)	12 Months Ended
Insurance Regulatory Restrictions (Notes)	Dec. 31, 2023
Regulatory Assets and Liabilities Disclosure [Abstract]
Insurance Regulatory Restrictions	8. INSURANCE REGULATORY RESTRICTIONS United States AAC is domiciled in the State of Wisconsin and, as such, it is subject to the insurance laws and regulations of the State of Wisconsin (the “Wisconsin Insurance Laws”) and is regulated by the OCI as a domestic insurer. Everspan Indemnity and its wholly owned subsidiary, Everspan Insurance Company ("Everspan Insurance"), are domiciled in Arizona and are subject to the insurance laws and regulations of Arizona (the “Arizona Insurance Laws”) and are regulated by the Arizona Department of Insurance and Financial Institutions as domestic insurers. The other subsidiaries of Everspan Insurance (Providence Washington Insurance Company, Greenwood Insurance Company, Consolidated National Insurance Company and Consolidated Specialty Insurance Company; together with Everspan Insurance, the "Everspan Admitted Carriers") are domiciled in various States and are therefore subject to the insurance laws and regulations of their respective States of domicile (together with the Wisconsin Insurance Laws and the Arizona Insurance Laws, the “State Insurance Laws”) and regulated by the insurance departments of those States as domestic insurers. In addition, AAC and the Everspan Admitted Carriers are subject to the insurance laws and regulations of the other jurisdictions in which they are licensed and operate as foreign insurers. Insurance laws and regulations applicable to insurers vary by jurisdiction, but the insurance laws and regulations applicable to our insurance carriers generally require them to maintain minimum standards of business conduct and solvency; to meet certain financial tests; and to file policy forms, premium rate schedules and certain reports with regulatory authorities, including information concerning capital structure, ownership, financial condition (such as risk-based capital), corporate governance and enterprise risk. AAC, because it is a financial guarantee insurer, is not subject to risk-based capital requirements. As a run-off financial guarantor, AAC has been operating under the Stipulation and Order required by OCI. OCI has developed and implemented OCI's Runoff Capital Framework to assist OCI with decision making related to capital and liquidity management at AAC. OCI cannot require AFG or any other Ambac entity to contribute capital to or otherwise support AAC. See Note 1. Background and Business Description for additional information. Regulated insurance companies are also required to file quarterly and annual statutory financial statements in each jurisdiction in which they are licensed. The State Insurance Laws also require prior approval (or non-disapproval) of certain transactions between an insurance carrier and its affiliates. The level of supervisory authority that may be exercised by non-domiciliary insurance regulators varies by jurisdiction. Generally, however, non-domiciliary regulators are authorized to suspend or revoke the insurance license they issued and to impose restrictions on that license in the event that laws or regulations are breached by a regulated insurance company or in the event that continued or unrestricted licensing of the regulated insurance company constitutes a “hazardous condition” (or meets a similar standard) in the opinion of the non-domiciliary regulator. The domiciliary regulators have primary regulatory authority, including with respect to the initiation and administration of rehabilitation or liquidation proceedings. Additionally, the accounts and operations of AAC, Everspan Indemnity and the Everspan Admitted Carriers are subject to individual periodic comprehensive financial examinations by their domestic regulators, and may be examined collectively by the lead regulator of the affiliated insurance company group. In December 2020, Everspan Insurance completed its re-domestication from Wisconsin to Arizona and obtained broad authority to write property and casualty insurance (while contemporaneously surrendering its authority to write financial guaranty insurance) in Arizona. Everspan Insurance thereafter sought similar amendments to its certificates of authority in all other states. Everspan Indemnity and the Everspan Admitted Carriers (collectively, "Everspan") are subject to risk-based capital requirements. Everspan Indemnity was formed in 2020 as a domestic surplus lines insurer in Arizona and, accordingly, is eligible to write property and casualty insurance as an excess and surplus lines insurance in all states by virtue of the U.S. Nonadmitted and Reinsurance Reform Act of 2010. All of Ambac's insurance subsidiaries are in compliance with the minimum capital and surplus levels required under the State Insurance Laws required to transact all business written to date. Our Insurance Distribution businesses, like some other managing general agents, brokerages and program administrators, may be subject to licensing requirements and regulation by insurance regulators in various states in which they conduct business. In addition to the legal restrictions applicable to AAC as described herein, pursuant to the terms of the Settlement Agreement and the Stipulation and Order, AAC must seek prior approval by OCI of certain corporate actions. The Settlement Agreement and Stipulation and Order include covenants which restrict the operations of AAC. The Settlement Agreement will remain in force until the surplus notes that were issued pursuant to the Settlement Agreement have been redeemed, repurchased or repaid in full. The Stipulation and Order will remain in force for so long as OCI determines it to be necessary. Certain of the restrictions in the Settlement Agreement may be waived with the approval of the OCI and/or the requisite percentage of holders of AAC's surplus notes. See Note 1. Background and Business Description for additional information. Although not domiciled in New York, AAC is nevertheless subject to the New York insurance law governing financial guarantee insurers. New York’s comprehensive financial guarantee insurance law defines the scope of permitted financial guarantee insurance and governs the conduct of business of all financial guarantors licensed to do business in New York, including AAC. The New York financial guarantee insurance law also establishes single and aggregate risk limits with respect to insured obligations insured by financial guarantee insurers. Such single risk limits are specific to the type of insured obligation (for example, municipal or asset-backed). Under the aggregate limits, policyholders’ surplus and contingency reserves must at least equal a percentage of aggregate net liability that is equal to the sum of various percentages of aggregate net liability for various categories of specified obligations. At December 31, 2023, AAC is in compliance with applicable aggregate risk limits and applicable single risk limits. The financial statements of AAC and Everspan are prepared on the basis of accounting practices prescribed or permitted by the State Insurance Laws and the actions of regulatory authorities thereunder. AAC and Everspan use such statutory accounting practices prescribed or permitted by the applicable regulatory authorities for determining and reporting their financial condition and results of operations, including for determining solvency under the State Insurance Laws. The States in which AAC and Everspan are domiciled have adopted the National Association of Insurance Commissioners (“NAIC”) accounting practices and procedures manual (“NAIC SAP”) as a component of prescribed practices as codified in each State’s applicable law or regulation. Statutory policyholder surplus differs from stockholder's equity determined under GAAP principally due to statutory accounting rules that treat financial guarantee premiums and loss reserves, investments, net acquisition costs, consolidation of subsidiaries or variable interest entities and surplus notes differently. The following are details of statutory surplus for AAC and Everspan Indemnity: • AAC’s statutory policyholder surplus was $897 at December 31, 2023, as compared to $598 as of December 31, 2022. • Everspan Indemnity has statutory policyholder surplus of $108 as of December 31, 2023 as compared to $107 as of December 31, 2022. Everspan does not have permitted or additional prescribed practices at December 31, 2023 or December 31, 2022. The OCI has prescribed additional practices and has permitted accounting practices for AAC. As a result of the prescribed and permitted practices discussed below, AAC’s statutory surplus at December 31, 2023 and 2022 was lower by $24 and higher by $90, respectively, than if AAC had reported such amounts in accordance with NAIC SAP. Additional Prescribed Accounting Practices AAC: OCI has prescribed the following accounting practices that differ from NAIC SAP for AAC: • Paragraph 8 of Statement of Statutory Accounting Principles No. 60 “Financial Guaranty Insurance” allows for a deduction from loss reserves for the time value of money by application of a discount rate equal to the average rate of return on the admitted assets of the financial guaranty insurer as of the date of the computation of the reserve. The discount rate shall be adjusted at the end of each calendar year. Additionally, in accordance with paragraph 13.e of Statutory Accounting Principles No. 97 "Investments in Subsidiary, Controlled and Affiliated Entities" and paragraph 8 of Statutory Accounting Principles No. 5R “Liabilities, Contingencies and Impairments of Assets - Revised”, AAC records probable losses on its subsidiaries for which it guarantees their obligations. AAC also discounts probable losses on guarantees of subsidiary obligations using a discount rate equal to the average rate of return on its admitted assets. AAC’s average rates of return on its admitted assets at December 31, 2023 and 2022 were 5.86% and 3.22%, respectively. OCI has directed AAC to utilize a prescribed discount rate of 5.10% for the purpose of discounting both its loss reserves and its probable losses on subsidiary guarantees. • Paragraph 4 of Statement of Statutory Accounting Principles No. 41 “Surplus Notes” (“SSAP 41”) states that proceeds received by the issuer of surplus notes must be in the form of cash or other admitted assets having readily determinable values and liquidity satisfactory to the commissioner of the state of domicile. Under statutory accounting principles, surplus notes issued in conjunction with commutations or the settlement of obligations would be valued at zero upon issuance pursuant to paragraph 4, SSAP 41. OCI has directed the Company to record surplus notes issued in connection with commutations or the settlement of obligations at full par value upon issuance. The surplus notes issued have a claim against surplus senior to the preferred and common shareholders. • Paragraph 35 of Statement of Statutory Accounting Principles No. 43R ”Loan-backed and Structured Securities” states that when an other-than-temporary impairment ("OTTI") has occurred, the amount of the OTTI recognized as a realized loss shall equal the difference between the investment’s amortized cost basis and the present value of cash flows expected to be collected, discounted at the loan-backed or structured security’s effective interest rate. From June 11, 2014 to February 12, 2018, OCI had directed AAC to not evaluate for OTTI investments in AAC insured securities with designated policies that were allocated to a segregated account of AAC in rehabilitation overseen by OCI, and required all such investments be reported at amortized cost regardless of its NAIC risk designation. Permitted Accounting Practices AAC: OCI has allowed the following permitted practice for AAC: • Wisconsin accounting practices for changes to contingency reserves differ from NAIC SAP. Under NAIC SAP, contributions to and releases from the contingency reserve are recorded via a direct charge or credit to surplus. Under the Wisconsin Administrative Code, contributions to and releases from the contingency reserve are to be recorded through underwriting income. AAC received permission from OCI to record contributions to and releases from the contingency reserve, in accordance with NAIC SAP. United Kingdom The Prudential Regulatory Authority (“PRA”) and Financial Conduct Authority (“FCA”) (and their predecessor regulator the Financial Services Authority (“FSA”)) are the dual statutory regulator responsible for regulating the financial services industry in the United Kingdom, with the purpose of maintaining confidence in the U.K. financial system, providing public understanding of the system, securing the proper degree of protection for consumers and helping to reduce financial crime. These regulators have exercised significant oversight of Ambac UK since 2008, after Ambac, AAC and Ambac UK began experiencing financial stress. In 2009, Ambac UK’s license to write new business was curtailed by the FSA and the insurance license was limited to undertaking only run-off related activity. As such, Ambac UK is authorized to run-off its credit, suretyship and financial guarantee insurance portfolio in the United Kingdom. The PRA requires that non-life insurance companies such as Ambac UK maintain a margin of solvency at all times in respect of the liabilities of the insurance company, the calculation of which depends on the type and amount of insurance business a company writes. These solvency requirements were amended on January 1, 2016, in order to implement the European Union's "Solvency II" directive on risk-based capital. Ambac UK had previously been in a capital shortfall position as compared to these solvency capital requirements, but has met the requirements since December 31, 2021. Dividend Restrictions, Including Contractual Restrictions United States State Insurance Regulators prescribe rules that determine if AAC and Everspan may declare dividends. In addition, AAC and Everspan are subject to certain restrictions in their respective articles of incorporation with regards to the payment of dividends. Board action authorizing a distribution by an insurance company must generally be reported to the applicable domiciliary regulator prior to payment. In addition, State Insurance Laws generally require regulatory approval for the payment of extraordinary dividends, which are distributions in amounts that would exceed certain thresholds, such as a percentage of surplus or net income for the prior year or number of years. Everspan does not have sufficient earned surplus at this time to pay ordinary dividends under the State Insurance Laws. Furthermore, certain subsidiaries of Everspan Insurance are restricted from paying dividends to Everspan Insurance until 2025 or later pursuant to the regulatory orders approving the acquisition of those subsidiaries, unless specifically approved by the applicable domiciliary regulator. Due to losses experienced by AAC, AAC has been unable to pay ordinary dividends to AFG since 2008 and will be unable to pay common dividends in 2024 without the prior consent of the OCI, which is extremely unlikely. AAC’s ability to pay dividends is further restricted by the Settlement Agreement (as described below), by the terms of its AMPS (as described below) and by the Stipulation and Order, and decisions by OCI concerning dividends or other releases of capital in respect of AAC's debt and equity will be affected by OCI's Runoff Capital Framework. See Note 1. Background and Business Description for further information. Accordingly, AAC's ability to pay dividends to AFG and the timing thereof remain subject to substantial uncertainty. • Pursuant to the Settlement Agreement, AAC may not make any “Restricted Payment” (which includes dividends from AAC to Ambac) in excess of $5 in the aggregate per annum, other than Restricted Payments from AAC to Ambac in an amount up to $7.5 per annum solely to pay operating expenses of Ambac. Concurrent with making any such Restricted Payment, a pro rata amount of AAC's surplus notes would also need to be redeemed at par. • Under the terms of AAC’s AMPS, dividends may not be paid on the common stock of AAC unless all accrued and unpaid dividends on the AMPS for the then current dividend period have been paid, provided, that dividends on the common stock may be made at all times for the purpose of, and only in such amounts as are necessary for, enabling Ambac (i) to service its indebtedness for borrowed money as such payments become due or (ii) to pay its operating expenses. If dividends are paid on the common stock as provided in the prior sentence, dividends on the AMPS become cumulative until the date that all accumulated and unpaid dividends have been paid on the AMPS. • The Stipulation and Order requires OCI approval for the payment of any dividend or distribution on the common stock of AAC. • OCI's Runoff Capital Framework and decisions based thereon may affect AAC's ability to pay dividends to AFG. United Kingdom UK law prohibits Ambac UK from declaring a dividend to its shareholders unless it has “profits available for distribution.” The determination of whether a company has profits available for distribution is based on its accumulated realized profits less its accumulated realized losses. Further, the FSA amended Ambac UK’s license in 2010 such that the PRA must specifically approve (“non-objection”) any transfer of value and/or assets from Ambac UK to AAC or any other Ambac group company, other than in respect of certain disclosed contracts between the two parties (such as in respect of a management services agreement between AAC and Ambac UK).

Derivative Instruments

Derivative Instruments	12 Months Ended
Derivative Instruments	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	9. DERIVATIVE INSTRUMENTS The following tables summarize the location and gross fair values of individual derivative instruments and the impact of legal rights of offset as reported in the Consolidated Balance Sheets, as of December 31, 2023 and 2022. December 31, 2023: December 31, 2022: Gross Gross Net Amounts Gross Amount Net Amount Gross Gross Net Amounts Gross Amount Net Amount Other assets: Interest rate swaps $ 25 $ — $ 25 $ — $ 25 $ 27 $ — $ 27 $ — $ 27 Warrants 1 — 1 — 1 1 — 1 — 1 Total non-VIE derivative assets $ 26 $ — $ 26 $ — $ 26 $ 28 $ — $ 27 $ — $ 27 Other liabilities: Interest rate swaps $ 35 $ — $ 35 $ 35 $ — $ 38 $ — $ 38 $ 38 $ — Total non-VIE derivative liabilities $ 35 $ — $ 35 $ 35 $ — $ 38 $ — $ 38 $ 38 $ — Variable interest entities assets: Derivative and other assets: Interest rate swaps $ 190 $ — $ 190 $ 190 $ — $ 190 $ — $ 190 $ — $ 190 Currency swaps 36 — 36 36 — $ 49 $ — $ 49 $ — $ 49 Total VIE derivative assets $ 226 $ — $ 226 $ 226 $ — $ 239 $ — $ 239 $ — $ 239 Variable interest entities liabilities: Derivative liabilities: Interest rate swaps $ 1,197 $ — $ 1,197 $ — $ 1,197 $ 1,048 $ — $ 1,048 $ — $ 1,048 Total VIE derivative liabilities $ 1,197 $ — $ 1,197 $ — $ 1,197 $ 1,048 $ — $ 1,048 $ — $ 1,048 Amounts representing the right to reclaim cash collateral or the obligation to return cash collateral are not offset against fair value amounts recognized for derivative instruments on the Consolidated Balance Sheets. The amounts representing the right to reclaim cash collateral and posted margin, recorded in “Other assets” were $23 and $6 as of December 31, 2023 and 2022, respectively. Amounts representing an obligation to return cash collateral were $235 and $0 as of December 31, 2023 and 2022, respectively and are reported in "Variable interest entity liabilities: Other liabilities". The following tables summarize the location and amount of gains and losses of derivative contracts in the Consolidated Statements of Total Comprehensive Income (Loss) for the years ended December 31, 2023, 2022 and 2021: Location of Gain (Loss) Recognized Amount of Gain (Loss) Recognized in Consolidated Statement of Total Comprehensive Income (Loss) – 2023 2022 2021 Non-VIE derivatives: Interest rate swaps Net gains (losses) on derivative contracts (1) 65 13 Warrants Net gains (losses) on derivative contracts — 1 — Futures contracts Net gains (losses) on derivative contracts — 62 9 Total Non-VIE derivatives (1) 129 22 Variable Interest Entities: Currency swaps Income (loss) on variable interest entities (1) 24 2 Interest rate swaps Income (loss) on variable interest entities (62) 541 (152) Total Variable Interest Entities (63) 565 (150) Total derivative contracts $ (64) $ 694 $ (128) Interest Rate Derivatives AFS provided interest rate derivatives to financial guarantee customers and used derivatives to provide a partial hedge against interest rate risk in AAC's insurance and investment portfolios. Since June 30, 2023, AFS's only remaining derivative positions include a limited number of legacy customer swaps and their associated hedges. As of December 31, 2023 and 2022, the notional amounts of AFS's derivatives are as follows: Notional - December 31, Type of Derivative 2023 2022 Interest rate swaps—pay-fixed/receive-variable $ 141 $ 989 Interest rate swaps—receive-fixed/pay-variable 167 337 Warrants: At December 31, 2023 and 2022, Ambac holds warrants to purchase preferred stock of a development stage company. Derivatives of Consolidated Variable Interest Entities Certain VIEs consolidated under the Consolidation Topic of the ASC entered into derivative contracts to meet specified purposes within the securitization structure. The notional for VIE derivatives outstanding as of December 31, 2023 and 2022, were as follows: Notional - December 31, Type of VIE Derivative 2023 2022 Interest rate swaps—receive-fixed/pay-variable $ 1,662 $ 1,573 Interest rate swaps—pay-fixed/receive-variable 864 887 Currency swaps 149 176 Contingent Features in Derivatives Related to Ambac Credit Risk Certain interest rate swaps remain with professional swap-dealer counterparties executed under standardized derivative documents including collateral support and master netting agreements. Under these agreements, Ambac is required to post collateral in the event net unrealized losses exceed predetermined threshold levels. Additionally, given that AAC is no longer rated by an independent rating agency, counterparties have the right to terminate the swap positions. As of December 31, 2023 and 2022, the net liability fair value of derivative instruments with contingent features linked to Ambac’s own credit risk was $35 and $38, respectively, related to which Ambac had posted cash and securities as collateral with a fair value of $50 and $54, respectively. All such ratings-based contingent features have been triggered requiring maximum collateral levels to be posted by Ambac while preserving counterparties’ rights to terminate the contracts. Assuming all such contracts terminated at fair value on December 31, 2023, settlement of collateral balances and net derivative liabilities would result in a net receipt of cash and/or securities by Ambac. If counterparties elect to exercise their right to terminate, the actual termination payment amounts will be determined in accordance with derivative contract terms, which may result in amounts that differ from market values as reported in Ambac’s financial statements.

Intangible Assets

Intangible Assets	12 Months Ended
Intangible Assets	Dec. 31, 2023
Statement of Financial Position [Abstract]
Goodwill and Intangible Assets Disclosure	10. GOODWILL AND INTANGIBLE ASSETS The following table presents a rollforward of goodwill at December 31, 2023 and 2022. December 31, 2023 2022 Beginning balance $ 61 $ 46 Business acquisitions 9 15 Impairments — — Ending balance $ 70 $ 61 Intangible asset and accumulated amortization are included in the Consolidated Balance Sheets, as shown below. December 31, 2023 2022 Finite-lived Intangible Assets: Insurance intangible: Gross carrying value $ 1,258 $ 1,247 Accumulated amortization 1,013 981 Net insurance intangible asset 245 266 Other intangibles: Gross Carrying value 57 52 Accumulated amortization 10 6 Net other intangible assets 47 47 Total finite-lived intangible assets $ 292 $ 312 Indefinite-lived Intangible Assets: Insurance licenses $ 14 $ 14 Total intangible assets $ 307 $ 326 Amortization Expense: Amortization expense is included in the Consolidated Statements of Total Comprehensive Income (Loss), as shown below. Year ended December 31, 2023 2022 2021 Insurance intangible $ 25 44 $ 52 Other intangibles 4 3 3 Total $ 29 $ 47 $ 55 The estimated future amortization expense for finite-lived intangible assets is as follows: Amortization Expense Insurance Intangible Asset (1) Other Intangible Assets (1) Total 2024 $ 26 $ 5 $ 30 2025 24 4 28 2026 22 4 26 2027 20 4 24 2028 18 4 22 Thereafter 136 26 162 (1)

Variable Interest Entities

Variable Interest Entities	12 Months Ended
Variable Interest Entities	Dec. 31, 2023
Accounting Policies [Abstract]
Variable Interest Entity Disclosure	11. VARIABLE INTEREST ENTITIES Ambac, with its subsidiaries, has engaged in transactions with variable interest entities ("VIEs") in various capacities. • AAC and Ambac UK provide financial guarantees for various debt obligations issued by special purpose entities, including VIEs ("LFG VIEs"); • Ambac sponsors special purpose entities that issued notes to investors for various purposes; and • AAC and Ambac UK invest in collateralized debt obligations, mortgage-backed and other asset-backed securities issued by VIEs and their ownership interest is generally insignificant to the VIE and/or they do not have rights that direct the activities that are most significant to such VIE. LFG VIEs AAC and Ambac UK provide financial guarantees in respect of assets held or debt obligations of VIEs. AAC and Ambac UK’s primary variable interest exists through this financial guarantee insurance. The transaction structures provide certain financial protection to AAC or Ambac UK. Generally, upon deterioration in the performance of a transaction or upon an event of default as specified in the transaction legal documents, AAC or Ambac UK will obtain certain control rights that enable them to remediate losses. These rights may enable them to direct the activities of the entity that most significantly impact the entity’s economic performance. Under the Stipulation and Order, AAC is required to obtain OCI approval with respect to the exercise of certain significant control rights in connection with policies that had previously been allocated to the Segregated Account. Accordingly, AAC does not have the right to direct the most significant activities of those LFG VIEs. • We determined that AAC or Ambac UK generally have the obligation to absorb a LFG VIE's expected losses given that they have issued financial guarantees supporting certain liabilities (and in some cases certain assets). As further described below, Ambac consolidates certain LFG VIEs in cases where we also have the power to direct the activities that most significantly impact the VIE’s economic performance due to one or more of the following: (i) the transaction experiencing deterioration and breaching performance triggers, giving AAC or Ambac UK the ability to exercise certain control rights, (ii) AAC or Ambac UK being involved in the design of the VIE and receiving control rights from its inception, such as may occur from loss remediation activities, or (iii) the transaction not experiencing deterioration, however due to the passive nature of the VIE, AAC or Ambac UK's contingent control rights upon a future breach of performance triggers is considered to be the power over the most significant activity. • A VIE is generally deconsolidated in the period that AAC or Ambac UK no longer has such control rights, which could occur in connection with the execution of remediation activities on the transaction or amortization of insured exposure, either of which may reduce the degree of control over a VIE. • Assets and liabilities of LFG VIEs that are consolidated are reported within Variable interest entity assets or Variable interest entity liabilities on the Consolidated Balance Sheets. • The election to use the fair value option is made on an instrument by instrument basis. Generally, Ambac has elected the fair value option for consolidated LFG VIE financial assets and financial liabilities, except in cases where AAC or Ambac UK was involved in the design of the VIE and was granted control rights at its inception or when the financial liabilities are primarily supported by non-financial assets. ◦ When the fair value option is elected, changes in the fair value of the LFG VIE's financial assets and liabilities are reported within Income (loss) on variable interest entities in the Consolidated Statements of Total Comprehensive Income (Loss), except for the portion of the total change in fair value of financial liabilities caused by changes in the instrument-specific credit risk which is presented separately in Other comprehensive income (loss). ◦ In cases where the fair value option has not been elected, the LFG VIE's invested assets are fixed maturity securities and are classified as either available-for-sale or trading as defined by the Investments - Debt Securities Topic of the ASC. Available-for-sale assets are reported in the financial statements at fair value with unrealized gains and losses reflected in Accumulated Other Comprehensive Income (Loss) in Stockholders' Equity. Trading assets are reported at fair value with unrealized gains and losses reflected within net income. When the fair value option has not been elected for LFG VIE long term debt obligations, the debt is carried at par less unamortized discount. Income from the LFG VIE's securities (including investment income, realized gains and losses and credit impairments as applicable) and interest expense on long term debt are reported within Income (loss) on variable interest entities in the Consolidated Statements of Total Comprehensive Income (Loss). • Upon initial consolidation of a LFG VIE, Ambac recognizes a gain or loss in earnings for the difference between: (i) the fair value of the consideration paid, the fair value of any non-controlling interests and the reported amount of any previously held interests and (ii) the net amount of the assets and liabilities consolidated, measured on a fair value basis except for contract assets and liabilities which are measured at the date of consolidation consistent with the accounting under the revenue recognition standard. Upon deconsolidation of a LFG VIE, Ambac recognizes a gain or loss for the difference between: (i) the fair value of any consideration received, the fair value of any retained non-controlling investment in the VIE and the carrying amount of any non-controlling interest in the VIE and (ii) the carrying amount of the VIE’s assets and liabilities. Gains or losses from consolidation and deconsolidation that are reported in earnings are reported within Income (loss) on variable interest entities on the Consolidated Statements of Total Comprehensive Income (Loss). • The impact of consolidating such LFG VIEs on Ambac’s balance sheet is the elimination of transactions between the consolidated LFG VIEs and AAC or Ambac UK and the inclusion of the LFG VIE’s third party assets and liabilities. For a financial guarantee insurance policy issued to a consolidated VIE, Ambac does not reflect the financial guarantee insurance policy in accordance with the related insurance accounting rules under the Financial Services — Insurance Topic of the ASC. Consequently, upon consolidation, Ambac eliminates the insurance assets and liabilities associated with the policy from the Consolidated Balance Sheets. Such insurance assets and liabilities may include premium receivables, reinsurance recoverable, deferred ceded premium, subrogation recoverable, unearned premiums, loss and loss expense reserves, ceded premiums payable and insurance intangible assets. For investment securities owned by AAC or Ambac UK that are debt instruments issued by the VIE, the associated debt and investment balances are eliminated upon consolidation. LFG VIEs which are consolidated may include recourse and non-recourse liabilities. LFG VIEs' liabilities that are insured by AAC or Ambac UK are with recourse, because the AAC or Ambac UK guarantees the payment of principal and interest in the event the issuer defaults. LFG VIEs' liabilities that are not insured by the AAC or Ambac UK are without recourse, because AAC or Ambac UK has not issued a financial guarantee and is under no obligation for the payment of principal and interest of these instruments. AAC or Ambac UK’s economic exposure to consolidated LFG VIEs is limited to the financial guarantees issued for recourse liabilities and any additional variable interests held by them. Additionally, AAC or Ambac UK’s general creditors, other than those specific policy holders which own the VIE debt obligations, do not have rights with regard to the assets of the VIEs. Ambac evaluates the net income effects and earnings per share effects to determine attributions between AAC or Ambac UK and non-controlling interests as a result of consolidating a VIE. Ambac has determined that the net income and earnings per share effect of consolidated LFG VIEs are attributable to AAC or Ambac UK’s interests through financial guarantee premium and loss payments with the VIE. The following table summarizes the carrying values of assets and liabilities, along with other supplemental information related to VIEs that are consolidated as a result of financial guarantees of Ambac UK and AAC: December 31, 2023 2022 Ambac UK Ambac Assurance Total VIEs Ambac UK Ambac Assurance Total VIEs ASSETS: Fixed maturity securities, at fair value: Corporate obligations, fair value option $ 2,072 $ — $ 2,072 $ 1,828 $ — $ 1,828 Municipal obligations, trading — — — — 43 43 Municipal obligations, available-for-sale (1) — 95 95 — 96 96 Total LFG VIE fixed maturity securities, at fair value 2,072 95 2,167 1,828 139 1,967 Restricted cash 245 1 246 1 16 17 Loans, at fair value (2) 1,663 — 1,663 1,829 — 1,829 Derivative assets 226 — 226 239 — 239 Other assets, including contract assets 90 2 92 — 2 2 Total LFG VIE assets $ 4,296 $ 98 $ 4,394 $ 3,896 $ 157 $ 4,054 LIABILITIES: Long-term debt: Long-term debt, at fair value (3) $ 2,710 $ — $ 2,710 $ 2,788 $ — $ 2,788 Long-term debt, at par less unamortized discount 99 159 258 — 319 319 Total long-term debt 2,808 159 2,967 2,788 319 3,107 Derivative liabilities 1,197 — 1,197 1,048 — 1,048 Cash collateral payable 235 — 235 — — — Other liabilities 4 1 5 — 5 5 Total LFG VIE liabilities $ 4,244 $ 160 $ 4,404 $ 3,836 $ 324 $ 4,160 Number of LFG VIEs consolidated 4 2 6 5 4 9 (1) Available-for-sale LFG VIE fixed maturity securities consist of municipal obligations with an amortized cost basis of $88 and $99 at December 31, 2023 and December 31, 2022, respectively. At December 31, 2023, there were $7 aggregate gross unrealized gains and $0 aggregate gross unrealized losses. At December 31, 2022, there were $1 aggregate gross unrealized gain and $(4) aggregate gross unrealized losses. All such securities had contractual maturities due after ten years as of December 31, 2023. (2) The unpaid principal balances of loan assets carried at fair value were $1,787 and $1,977 as of December 31, 2023 and 2022, respectively. (3) The unpaid principal balances of long-term debt carried at fair value were $2,952 and $3,064 as of December 31, 2023 and 2022, respectively. The following schedule details the components of Income (loss) on variable interest entities for the affected periods: Year ended December 31, 2023 2022 2021 Net change in fair value of VIE assets and liabilities reported under the fair value option $ 4 $ — $ 4 Less: Credit risk changes of fair value option long-term debt reported through other comprehensive income (loss) — (1) 1 Net change in fair value of VIE assets and liabilities reported in earnings under the fair value option 5 (1) 5 Investment income (loss) 7 (4) 6 Net realized investment gains (losses) on available-for-sale securities 1 2 2 Interest expense on long-term debt carried at par less unamortized cost (12) (12) (6) Other expenses (1) (1) (1) Gain (loss) from consolidating VIEs 4 37 — Income (loss) on variable interest entities $ 3 $ 21 $ 7 Ambac consolidated an additional one, three and zero LFG VIEs during the years ended December 31, 2023, 2022 and 2021, respectively. Ambac deconsolidated four, zero and zero LFG VIEs during the years ended December 31, 2023, 2022 and 2021, respectively. No gains or losses resulted from the deconsolidations. The following table displays the carrying amount of the assets, liabilities and maximum exposure to loss of Ambac’s variable interests in non-consolidated VIEs resulting from financial guarantee and derivative contracts by major underlying asset classes, as of December 31, 2023 and 2022: December 31, 2023: December 31, 2022: Carrying Value of Assets and Liabilities Carrying Value of Assets and Liabilities Maximum (1) Insurance (2) Insurance (3) Net Derivative (Liabilities) (4) Maximum (1) Insurance (2) Insurance (3) Net Derivative (Liabilities) (4) Global structured finance: Mortgage-backed—residential $ 2,391 $ 135 $ 432 $ — $ 2,559 $ 266 $ 400 $ — Other consumer asset-backed 540 5 200 — 652 6 225 — Other 433 2 2 — 430 2 2 1 Total global structured finance 3,364 141 634 — 3,642 274 628 1 Global public finance 17,498 209 202 — 17,997 216 212 — Total $ 20,861 $ 351 $ 836 $ — $ 21,639 $ 490 $ 840 $ 1 (1) Maximum exposure to loss represents the maximum future payments of principal and interest on insured obligations and derivative contracts. Ambac’s maximum exposure to loss does not include the benefit of any financial instruments (such as reinsurance or hedge contracts) that Ambac may utilize to mitigate the risks associated with these variable interests. (2) Insurance assets represent the amount included in “Premium receivables” and “Subrogation recoverable” for financial guarantee insurance contracts on Ambac’s Consolidated Balance Sheets. (3) Insurance liabilities represent the amount included in “Loss and loss adjustment expense reserves” and “Unearned premiums” for financial guarantee insurance contracts on Ambac’s Consolidated Balance Sheets. (4) Net derivative assets (liabilities) represent the fair value recognized on interest rate swaps on Ambac’s Consolidated Balance Sheets. Ambac Sponsored Non-consolidated VIEs

Long-Term Debt (Notes)

Long-Term Debt (Notes)	12 Months Ended
Long-Term Debt (Notes)	Dec. 31, 2023
Debt Disclosure [Abstract]
Long-term Debt	12. LONG-TERM DEBT Long-term debt outstanding, excluding VIE long-term debt, was as follows: December 31, 2023 2022 Par Value Unamortized Discount Carrying Value Par Value Unamortized Discount Carrying Value Ambac Assurance: 5.1% Surplus Notes $ 519 $ (28) $ 491 $ 519 $ (42) $ 477 Tier 2 Notes — — — 146 — 146 Ambac UK Debt 41 (24) 17 41 (25) 16 Long-term debt $ 560 $ (52) $ 508 $ 706 $ (67) $ 639 Aggregated annual maturities of non-VIE long-term debt obligations (based on scheduled maturity dates as further discussed below) are as follows: 2024 $ 519 (1) 2025 — 2026 — 2027 — 2028 — Thereafter 41 Total $ 560 (1) Surplus Notes had a scheduled maturity date of June 7, 2020. OCI declined the request of Ambac Assurance to pay the principal amount of the surplus notes, plus all accrued and unpaid interest thereon, on June 7, 2020, June 7, 2021, June 7, 2022, and June 7 2023. As a result, the payment date for principal of the surplus notes was extended until OCI grants approval to make the payment. Interest will accrue, compounded on each anniversary of the original scheduled payment date or scheduled maturity date, on any unpaid principal or interest through the actual date of payment at 5.1% per annum. Included in the table above is the potential principal payment at the next scheduled payment date of June 7, 2024. Surplus Notes Ambac Assurance's surplus notes, with a par amount of $519 and $519 at December 31, 2023 and 2022, respectively, had a scheduled maturity of June 7, 2020, which has been extended until OCI grants approval to pay the principal of the surplus notes. The discount on surplus notes outstanding as of December 31, 2023, is being accreted into income at a weighted average effective interest rate of 6.6%. Surplus note principal and interest payments require the approval of OCI. In May 2023, OCI declined the request of AAC to pay the principal amount of the surplus notes, plus all accrued and unpaid interest thereon, on the then next scheduled payment date of June 7, 2023. As a result, the scheduled payment date for interest, and the scheduled maturity date for payment of principal of the surplus notes was extended until OCI grants approval to make the payment. Interest will accrue, compounded on each anniversary of the original scheduled payment date or scheduled maturity date, on any unpaid principal or interest through the actual date of payment, at 5.1% per annum. Holders of surplus notes have no rights to enforce the payment of the principal of, or interest on, surplus notes in the absence of OCI approval to pay such amount. The interest on the outstanding surplus notes were accrued for and AAC is accruing interest on the interest amounts following each scheduled payment date. Total accrued and unpaid interest for surplus notes outstanding to third parties was $475 at December 31, 2023. As required by the terms of surplus notes, AAC will continue to seek OCI’s approval to make payments of principal and interest on its surplus notes. OCI’s approval may be granted or denied in OCI’s sole discretion. Since the issuance of the surplus notes in 2010, OCI has declined to approve regular payments of interest on surplus notes, although the OCI has permitted two exceptional payments. Ambac can provide no assurance as to when or if surplus note principal and interest payments will be made. If OCI does not approve payments on or the acquisition of surplus notes over time, the ongoing accretion of interest on the notes may impair AAC's ability to extinguish the notes in full. Surplus notes are subordinated in right of payment to policyholder and other claims. Tier 2 Notes The Tier 2 Notes, issued on February 12, 2018, had a par value of $0 and $146 (including paid-in-kind interest of $0 and $49) at December 31, 2023 and 2022, respectively, and had a legal maturity of February 12, 2055. Interest on the Tier 2 Notes was at an annual rate of 8.50%. Other than upon payment of principal at redemption or maturity, interest payments were not due in cash on interest payment dates and were paid-in-kind and compounded on the last day of each calendar quarter. The Tier 2 Notes were recorded at a discount to par as any consideration paid that was directly related to the issuance of the Tier 2 Notes was capitalized and was part of the effective yield calculation. Ambac accreted the discount on the Tier 2 Notes into earnings at an effective interest rate of 9.9%. Ambac UK Debt The Ambac UK debt, issued in connection with the commutation of an exposure on June 18, 2019, has a par value of $41 and $41 at December 31, 2023 and 2022, and a legal maturity of May 2, 2036. Interest on the Ambac UK debt is at an annual rate of 0.00%. The Ambac UK debt was recorded at its fair value at the date of issuance. The discount on the debt is currently being accreted into income at an effective interest rate of 7.4%. Debt Redemptions and Extinguishments Net realized gains (losses) on extinguishment of debt reported in the Consolidated Statements of Total Comprehensive Income (Loss) for the years ended December 31, 2023, 2022 and 2021were $0, $81 and $33, respectively. In 2021, Sitka, issued $1,175 par amount of LIBOR plus 4.5% senior secured notes due 2026 (the “Sitka Senior Secured Notes”). In connection with the issuance and sale of the Sitka Senior Secured Notes, AAC issued a secured note to Sitka in the same amount and with the same interest rate and maturity date as the Sitka Senior Secured Notes (the "Sitka AAC Note"). Effective October 29, 2022, the Sitka AAC Note and Sitka Senior Secured Notes were wholly redeemed for $1,218 (a price equal to 103% of the principal amount plus accrued and unpaid interest) from the proceeds from the BOA Settlement Payment. Ambac recorded a loss of $53, the difference between the carrying value of the Sitka AAC Note and the redemption amount paid, excluding accrued interest. The Tier 2 Notes were partially redeemed on October 29, 2022, by approximately $213 from the BOA Settlement Payment and fully redeemed on January 15, 2023, primarily from the Nomura Settlement Payment. No gain or loss was recorded on the redemptions of the Tier 2 Notes. Refer to Note 1. Background and Business Description for further description of the BOA Settlement Payment and Nomura Settlement Payment. During the year ended December 31, 2022, surplus notes with aggregate par amount of $266 were acquired from third party holders at prices below the carrying value of the surplus notes including accrued interest, resulting in a gain of $134. During the year ended December 31, 2021, purchase agreements were executed under which AAC issued $280 aggregate principal amount (and the associated amount of accrued and unpaid interest thereon) to acquire all its remaining outstanding junior surplus notes. The Company recorded a gain of $33 arising from these purchases of junior surplus notes below their carrying values. Variable Interest Entities, Long-term Debt The variable interest entity notes were issued by consolidated VIEs. Ambac is the primary beneficiary of the VIEs as a result of providing financial guarantees on certain of the VIEs obligations. Consequently, Ambac has consolidated these variable interest entity notes and all other assets and liabilities of the VIEs. Ambac is not primarily liable for the debt obligations of these entities. Ambac would only be required to make payments on these debt obligations in the event that the issuer defaults on any principal or interest due and to the extent such obligations are guaranteed by Ambac. The total unpaid principal amount of outstanding long-term debt associated with VIEs

Revenue from Contract with Cust

Revenue from Contract with Customer	12 Months Ended
Revenue from Contract with Customer	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer	13. REVENUES FROM CONTRACTS WITH CUSTOMERS As further described in the Revenue Recognition section of Note 2. Basis of Presentation and Significant Accounting Policies , the Insurance Distribution businesses and a consolidated VIE have contracts that are subject to the Revenue from Contracts with Customers Topic of the ASC. The following table presents Insurance Distribution commission revenue recognized disaggregated by policy type for the years ended December 31, 2023, 2022 and 2021 : Year ended December 31, 2023 2022 2021 Employer stop loss $ 11 $ 9 $ 8 Affinity products 22 19 18 Commercial auto 12 2 — Marine 3 — — Professional liability 3 — — Other 1 — — Total 51 $ 31 $ 26 During the years ended December 31, 2023, 2022 and 2021, the amount of revenue recognized related to performance obligations satisfied in a previous period, inclusive of changes due to estimates was approximately $5, $6 and $8, respectively. As the VIE was consolidated on December 31, 2023, revenues have not yet been recognized. Receivables, Contract Assets and Liabilities The balances of receivables, contract assets and contract liabilities with customers were as follows: December 31, 2023 2022 Receivables $ 10 $ 7 Contract assets 95 5 Contract liabilities 1 1 Insurance Distribution Contract assets represent estimated future consideration related to base commissions and profit-sharing commissions that were recognized as revenue upon the placement of the policy, but are not yet billable or collectable. The Company does not have the right to bill or collect payment on i) base commissions until the related premiums from policyholders have been collected nor ii) profit-sharing commissions until after the contract year is completed. Contract liabilities represent advance consideration received from customers related to Employer stop loss base commissions that will be recognized over time as claims servicing is performed, which typically occurs between 17 and 20 months from contract inception. During the years ended December 31, 2023, 2022 and 2021, the Company recognized revenue that was included in the contract liability balance as of the beginning of the period of $1, $1 and $1, respectively. Consolidated VIE Contract assets of $87 represent future consideration related to service concession payments for already completed services that were recognized as revenue but are not yet due. There are no contract liabilities.

Comprehensive Income

Comprehensive Income	12 Months Ended
Comprehensive Income	Dec. 31, 2023
Equity [Abstract]
Comprehensive Income	14. COMPREHENSIVE INCOME The following tables detail the changes in the balances of each component of accumulated other comprehensive income for the affected periods: Year Ended December 31, 2023: Year ended December 31, 2022: Unrealized Gains (Losses) on Available- for Sale Securities (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency Translation (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Unrealized Gains (Losses) on Available- for Sale Securities (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency Translation (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Beginning Balance $ (71) $ 3 $ (184) $ (1) $ (253) $ 154 $ 4 $ (100) $ (1) $ 58 Other comprehensive income (loss) before reclassifications 31 3 40 — 74 (211) — (85) — (296) Amounts reclassified from accumulated other comprehensive income (loss) 21 (1) — — 19 (14) (1) — — (15) Net current period other comprehensive income (loss) 51 2 40 — 93 (225) (1) (85) — (310) Ending balance $ (20) $ 5 $ (144) $ (1) $ (160) $ (71) $ 3 $ (184) $ (1) $ (253) (1) All amounts are net of tax and noncontrolling interest. Amounts in parentheses indicate reductions to Accumulated Other Comprehensive Income. (2) Represents the changes in fair value attributable to instrument-specific credit risk of liabilities for which the fair value option is elected. The following table details the significant amounts reclassified from each component of accumulated other comprehensive income, shown in the above rollforward tables, for the affected periods: Details about Accumulated Other Amount Reclassified from Accumulated Affected Line Item in the Year Ended December 31, 2023 2022 Unrealized Gains (Losses) on Available-for-Sale Securities (1) $ 22 $ (17) Net realized investment gains (losses) (2) 3 Provision for income taxes $ 21 $ (14) Net of tax and noncontrolling interest Amortization of Postretirement Benefit Prior service cost $ (1) $ (1) Other income Actuarial gains (losses) (1) — Other income (1) (1) Total before tax — — Provision for income taxes $ (1) $ (1) Net of tax and noncontrolling interest Credit Risk Changes of Fair Value Option Liabilities $ — $ — Credit risk changes of fair value option liabilities — — Provision for income taxes — — Net of tax and noncontrolling interest Total reclassifications for the period $ 19 $ (15) Net of tax and noncontrolling interest (1) Net unrealized investment gains (losses) on available for sale securities are included in Ambac's Consolidated Statements of Comprehensive Income as a component of Accumulated Other Comprehensive Income. Changes in these amounts include reclassification adjustments to exclude from "Other comprehensive income (loss)" those items that are included as part of "Net income" for a period that has been part of "Other comprehensive income (loss)" in earlier periods.

Net Income Per Share

Net Income Per Share	12 Months Ended
Net Income Per Share	Dec. 31, 2023
Earnings Per Share [Abstract]
Net Income Per Share	15. NET INCOME PER SHARE As of December 31, 2023, 45,195,370 shares of AFG's common stock (par value $0.01) were issued and outstanding. Common shares outstanding increased by 221,613, during the year ended December 31, 2023, primarily due to settlements of employee restricted and performance stock units, partially offset by share repurchases. For the three years ended December 31, 2023, 2022 and 2021, 1,503, 0 and 132 warrants were exercised, respectively, resulting in an issuance of 29, 0 and 4 shares of common stock, respectively. As of April 30, 2023, all of AFG's outstanding warrants expired without being exercised. Share Repurchases On March 29, 2022, AFG's Board of Directors approved a share repurchase program authorizing up to $20 in share repurchases, with an expiration date of March 31, 2024, which may be terminated at any time. On May 5, 2022, the Board of Directors authorized an additional $15 in share repurchase. As of December 31, 2023, AFG repurchased 1,930,384 shares (including 325,068 shares in 2023) for $19 with an average purchase price of $9.70 per share, bringing the total unused authorized amount to $16. Earnings Per Share Calculation The numerator of the basic and diluted earnings per share computation represents net income (loss) attributable to common stockholders adjusted by the retained earnings impact of the adjustment to redemption value of redeemable noncontrolling interests under ASC 480. The redemption value adjustment is further described in the Redeemable Noncontrolling Interests section of Note 2. Basis of Presentation and Significant Accounting Policies . The following table provides a reconciliation of net income attributable to common stockholders to the numerator in the basic and diluted earnings per share calculation, together with the resulting earnings per share amounts: Year ended December 31, 2023 2022 2021 Net income (loss) attributable to common stockholders $ 4 $ 522 $ (17) Adjustment to redemption value (ASC 480) 5 3 (12) Numerator of basic and diluted EPS $ 8 $ 525 $ (28) Per Share: Basic $ 0.18 $ 11.48 $ (0.61) Diluted $ 0.18 $ 11.31 $ (0.61) The denominator of the basic earnings per share computation represents the weighted average common shares outstanding plus vested restricted stock units (together, "Basic Weighted Average Shares Outstanding"). The denominator of diluted earnings per share adjusts the basic weighted average shares outstanding for all potential dilutive common shares outstanding during the period. All potential dilutive common shares outstanding consider common stock deliverable pursuant to warrants, unvested restricted stock units and performance stock units granted under existing compensation plans. The following table provides a reconciliation of the common shares used for basic net income per share to the diluted shares used for diluted net income per share: Year Ended December 31, 2023 2022 2021 Basic weighted average shares outstanding 45,636,649 45,719,906 46,535,001 Effect of potential dilutive shares (1) : Warrants — — — Restricted stock units 164,752 144,194 — Performance stock units (2) 739,305 550,730 — Diluted weighted average shares outstanding 46,540,706 46,414,830 46,535,001 Anti-dilutive shares excluded from the above reconciliation Warrants — 4,877,617 4,877,653 Restricted stock units 135,058 177,119 475,333 Performance stock units (2) — — 700,915 (1) For the year ended December 31, 2021, Ambac had a net loss and accordingly excluded all potentially dilutive securities from the determination of diluted loss per share as their impact was anti-dilutive. (2) Performance stock units are reflected based on the performance metrics through the balance sheet date. Vesting of these units is contingent upon meeting certain performance metrics. Although a portion of these performance metrics have been achieved as of the respective period end, it is possible that awards may no longer meet the metric at the end of the performance period.

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	16. INCOME TAXES AFG files a consolidated Federal income tax return with its subsidiaries. AFG and its subsidiaries also file separate or combined income tax returns in various states, local and foreign jurisdictions. The following are the major jurisdictions in which Ambac and its subsidiaries operate and the earliest tax years subject to examination: Jurisdiction Tax Year United States 2010 New York State 2013 New York City 2018 United Kingdom 2020 Italy 2019 Consolidated Pretax Income (Loss) U.S. and foreign components of pre-tax income (loss) were as follows: Year Ended December 31, 2023 2022 2021 U.S. $ (29) $ 511 $ (32) Foreign 41 13 34 Total $ 12 $ 525 $ 2 Provision (Benefit) for Income Taxes The components of the provision (benefit) for income taxes were as follows: Year Ended December 31, 2023 2022 2021 Current taxes U.S. state and local $ 1 $ — $ 2 Foreign 8 7 10 Total current taxes 8 6 12 Deferred taxes Domestic (2) — — Foreign 1 (4) 6 Total deferred taxes $ (1) $ (4) $ 6 Provision for income taxes $ 7 $ 2 $ 18 The total effect of income taxes on net income and stockholders’ equity for the years ended December 31, 2023, 2022 and 2021 is as follows: Year Ended December 31, 2023 2022 2021 Total income taxes charged to net income $ 7 $ 2 $ 18 Income taxes charged (credited) to stockholders’ equity: Unrealized gains (losses) on investment securities, including foreign exchange 12 (47) (3) Change in retirement benefits (1) — — Credit Risk Changes to Fair Value Options — — — Valuation allowance to equity (9) 41 1 Total charged to stockholders’ equity: 2 (6) (2) Total effect of income taxes $ 9 $ (4) $ 16 Reconciliation of U.S. Federal Statutory Income Tax Rate to Actual Income Tax Rate The tax provisions in the accompanying Consolidated Statements of Total Comprehensive Loss reflect effective tax rates differing from prevailing Federal corporate income tax rates. The following is a reconciliation of these differences: Year Ended December 31, 2023 2022 2021 Tax on income (loss) at statutory rate $ 3 21 % $ 110 21 % $ — 21 % Changes in expected tax resulting from: Tax-exempt interest — — % (1) — % (2) (114) % Foreign taxes 9 70 % 4 1 % 8 448 % State Income Taxes — (1) % (1) — % 14 794 % Return to Provision 15 118 % — — % — — % Variable Interest Entities (24) (197) % 25 5 % — — % Valuation allowance 2 13 % (131) (25) % (4) (230) % Other, net 4 35 % (4) (1) % 1 72 % Tax expense on income (loss) $ 7 60 % $ 2 1 % $ 18 991 % Unrecognized Tax Positions The Company had no material unrecognized tax benefits at December 31, 2023 and 2022. Deferred Income Taxes The tax effects of temporary differences that give rise to significant portions of the deferred tax liabilities and deferred tax assets at December 31, 2023 and 2022, are presented below: December 31, 2023 2022 Deferred tax liabilities: Insurance intangible $ 51 $ 56 Unearned premiums and credit fees 23 24 Variable interest entities — 4 Other 3 1 Total deferred tax liabilities 77 85 Deferred tax assets: Net operating loss carryforward 714 725 Interest expense carryforward 58 66 Loss reserves 42 38 Debentures 22 15 State capital loss carryforward 8 8 Compensation 5 6 Investments — 6 Other 4 4 Subtotal deferred tax assets 853 867 Valuation allowance 795 796 Total deferred tax assets 58 70 Net deferred tax liability $ 19 $ 15 In accordance with the Income Tax Topic of the ASC, a valuation allowance is recognized if, based on the weight of available evidence, it is more-likely-than-not that some, or all, of the deferred tax asset will not be realized. As a result of the risks and uncertainties associated with future operating results, management believes it is more likely than not that the Company will not generate sufficient U.S. federal, state and/or local taxable income to recover the deferred tax operating assets and therefore maintains a full valuation allowance. The remaining net deferred tax liability of $19 is attributable to Ambac U.K. and is classified in other liabilities on the Consolidated Balance Sheet. NOL & Investment Interest Carryforward
Schedule of Net Operating Loss And Tax Credit Carryovers	As of December 31, 2023, the Company has (i) $3,400 of NOLs, which if not utilized will begin expiring in 2030, and will fully expire in 2042, and (ii) $274 of interest expense tax deduction carryover, which has an indefinite carryforward period but is limited in any particular year based on certain provisions.

Employment Benefit Plans (Notes

Employment Benefit Plans (Notes)	12 Months Ended
Employment Benefit Plans (Notes)	Dec. 31, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Compensation and Employee Benefit Plans [Text Block]	17. EMPLOYMENT BENEFIT PLANS Incentive Compensation - Stock Units and Cash Employees, directors and consultants of Ambac are eligible to participate in Ambac’s 2020 Incentive Plan, which is the successor plan to the 2013 Incentive Plan, subject to the discretion of the Compensation Committee of Ambac’s Board of Directors. There are 1,475,000 and 4,000,000 shares of Ambac's common stock authorized for awards under the 2020 Plan and 2013 Plan, respectively. Awards may also be made under the 2020 Plan with respect to the shares that remained available for grant under the 2013 Plan. In addition, shares subject to outstanding awards granted under the 2013 Plan that subsequently terminate by expiration or forfeiture, cancellation, or otherwise without the issuance of such shares become available for awards under the 2020 Plan. On June 24, 2021, the Compensation Committee of Ambac's Board of Directors adopted the Ambac Financial Group, Inc. Executive Stock Deferral Plan (the “Stock Deferral Plan”). Under the Stock Deferral Plan, certain executives of AFG and its subsidiaries who are designated by the compensation committee as eligible to participate in the Stock Deferral Plan may elect to defer the settlement of all or a portion of the RSU (as defined below) awards and PSU (as defined below) awards that are granted to the executives to a future date(s) selected by the executive. Deferred awards under the Stock Deferral Plan (and any related dividend equivalents) will continue to be paid in shares of common stock of AFG, which will be issued under the 2020 Plan, provided that any dividend equivalents credited on a participant’s deferred awards in respect of cash dividends paid by AFG will be paid to the participant in cash. At the discretion of the Compensation Committee of the Board of Directors, RSU and PSU awards may be settled in cash based on the closing price of AFG's common stock on the last business day prior to the settlement date. The Stock Deferral Plan is not funded, and deferred awards under the Stock Deferral Plan are not segregated from the Company’s general assets. The amount of stock-based compensation expense and corresponding after-tax expense are as follows: Year Ended December 31, 2023 2022 2021 Restricted stock units $ 5 $ 5 $ 5 Performance awards 12 12 10 Total stock-based compensation $ 17 $ 17 $ 14 Total stock-based compensation (after-tax) $ 17 $ 17 $ 11 Restricted Stock Units (“RSUs”) RSUs can be awarded to certain employees for a portion of their STIP compensation, LTIP compensation, sign-on and special awards for exceptional performance or promotion. RSUs can also be awarded to consultants for meeting certain contractual performance goals. The LTIP, sign-on, consultant and special awards generally vest in equal installments over a two to three year period. Such vesting is expressly conditioned upon continued service with Ambac through the applicable vesting date, although vesting may be accelerated in certain circumstances under the awards, including for terminations due to death, disability, eligible retirement, or involuntary termination by Ambac other than for cause. As part of our director compensation program, prior to 2021 RSUs were awarded annually on or about April 30 of each year to directors and would vest on the last day of April of the following year. During 2021, the director compensation program was revised to provide for quarterly grants of RSUs that would vest one year from the grant date. These RSUs will not settle until the respective director’s termination from the Board of Directors or, if earlier, upon a change in control. All RSUs provide for accelerated vesting upon a change in control, death or disability or involuntary removal other than for cause (not including removal pursuant to a shareholder vote at a regularly scheduled annual meeting of shareholders). Upon termination (other than for cause), the unvested RSUs shall partially vest as of the date of such termination in an amount equal to the number of then outstanding unvested RSUs multiplied by a fraction, the numerator of which shall be the number of calendar days which have lapsed since the grant date and the denominator of which shall be the number of calendar days from the grant date until the next regularly scheduled quarterly grant date pursuant to Ambac’s director compensation program. As of December 31, 2023, 1,036,339 RSUs remained outstanding, of which (i) 634,312 units required future service as a condition to the delivery of the underlying shares of common stock and (ii) 402,027 units do not require future service and are deferred for future settlement. As of December 31, 2022, 923,250 RSUs remained outstanding, of which (i) 538,163 units required future service as a condition to the delivery of the underlying shares of common stock, and (ii) 385,087 units did not require future service and were deferred for future settlement. A summary of RSU activity for 2023 is as follows: Shares Weighted Average Grant Date Fair Value Per Share Outstanding at beginning of period 923,250 $ 15.94 Granted 415,416 15.72 Delivered or returned to plan (1) (300,164) 16.28 Forfeited (2,163) 16.97 Outstanding at end of period 1,036,339 $ 15.75 (1) When restricted stock unit awards issued by Ambac become taxable compensation to employees, shares may be withheld to cover the employee’s withholding taxes. For the year ended December 31, 2023, Ambac withheld 49,870 shares from employees that settled restricted stock units to meet the required tax withholdings. Ambac’s closing share price on the grant date was used to estimate the fair value of the service condition based RSU on the grant date. The weighted average grant date fair value per share of RSUs granted during 2023, 2022 and 2021 was $15.72, $12.48 and $17.39, respectively. As of December 31, 2023, there was $6 of total unrecognized compensation costs related to unvested RSUs granted. These costs are expected to be recognized over a weighted average period of 2.0 years. The fair value for RSUs vested and delivered during the year ended December 31, 2023, 2022 and 2021 was $5, $4 and $4, respectively. Performance Stock Awards ("PSUs") PSUs are awarded to certain employees for a portion of their LTIP compensation and vest after 3 years from grant date. The actual number of shares payable at settlement is subject to performance metrics relative to AFG, Cirrata, Xchange, Everspan and AAC. Actual payout can range from 0% to 240% of the number of units granted. Under currently outstanding award agreements, performance will be evaluated as follows: • In regards to Xchange, for the 2021 and 2022 PSU awards, and Cirrata for the 2023 PSU awards, (i) cumulative earnings before interest, taxes, depreciation and amortization over the vesting period and (ii) for Cirrata 2023 PSU awards, the aggregate of all premiums placed by Cirrata with any insurance carrier over the vesting period. • In regards to Everspan: (i) for the 2022 and 2023 PSU awards, cumulative earnings before interest, taxes, depreciation and amortization over the vesting period and (ii) for the 2023 PSU award, cumulative direct or assumed premiums written (including any from Cirrata) and fronting fees over the vesting period. • In regards to AAC: reductions in watch list and adversely classified credits, which is intended to reward participants for de-risking the financial guarantee insured portfolio. • Relative Total Shareholder Return will cause the payout at the end of the performance period to be increased or decreased 10% for awards issued through 2021 and 20% for awards after 2021, if AFG's stock performance compared to a peer group is at or above the 75th percentile or at or below the 25th percentile, respectively . Pursuant to the LTIP award agreements if (i) a termination occurred prior to the last day of the performance period by reason of disability, an involuntary termination by the Company other than for “cause,” or "retirement," the recipient would be entitled to receive the PSU award at the end of the relevant performance period based on the satisfaction of the performance conditions related to such award at the time of termination, and (ii) a termination occurred prior to the last day of the performance period by reason of death, the beneficiaries of the recipient would be entitled to receive the number of PSUs that the recipient would have been entitled to receive at a 100% overall payout multiple regardless of the outcome of any of the performance conditions. The current performance awards shall be settled within 75 days after the end of the performance period, including those with partial or accelerated vesting, subject to any deferrals made pursuant to the Stock Deferral Plan. A summary of PSU activity for 2023 is as follows: Shares Weighted Average Outstanding at beginning of period 918,951 $ 15.67 Granted (1) 479,079 17.72 Delivered (2) (525,212) 18.90 Forfeited (1,289) 17.72 Performance adjustment (3) 147,542 19.50 Outstanding at end of period 1,019,071 $ 15.52 (1) Represents performance share units at 100% of units granted for LTIP Awards. (2) Reflects the number of performance shares attributable to the performance goals attained over the completed performance period and for which service conditions have been met. When performance stock unit awards issued by Ambac become taxable compensation to employees, shares may be withheld to cover the employee’s withholding taxes. For the year ended December 31, 2023, Ambac withheld 231,645 of shares from employees that settled performance based restricted stock units to meet the required tax withholdings. (3) Represents the number of additional shares issued for awards granted in 2020 as a result of actual performance during the performance period. The weighted average grant date fair value per share of PSUs granted during 2023, 2022 and 2021 was $17.72, $13.44 and $18.67, respectively. As As of December 31, 2023, there was $10 of total unrecognized compensation costs related to the PSU portion of unvested performance awards, which are expected to be recognized over a weighted average period of 1.7 years. The fair value for PSUs vested and delivered during the year ended December 31, 2023, 2022 and 2021 was $8, $5 and $10, respectively.

Leases (Notes)

Leases (Notes)	12 Months Ended
Leases (Notes)	Dec. 31, 2023
Leases of Lessee Disclosure [Text Block]	18. LEASES Ambac is the lessee and lessor under certain lease agreements further described below. Lessee information Ambac is the lessee in operating leases for corporate offices, auto and equipment. Leases in effect at December 31, 2023, have remaining lease terms ranging from under 1 year to 9 years. Certain of these leases include automatic renewal or early termination provisions. Ambac does not include these provisions in the determination of its lease liabilities and right-of-use assets unless exercise is considered reasonably certain. Lease costs are included in operating expenses on the Consolidated Statement of Total Comprehensive Income (Loss). The components of lease costs, net of sub-lessor income, is as follows: Year Ended December 31, 2023 2022 Operating lease cost $ 4 $ 4 Short-term lease cost — — Variable lease cost 1 — Sublease income (1) (1) Total lease cost $ 4 $ 4 Ambac is required to make variable lease payments under certain leases which primarily relates to variable costs of the lessor, such as taxes, insurance, maintenance and electricity. Supplemental information related to leases is as follows: Year Ended December 31, 2023 2022 Cash paid for amounts included in the measurement of operating lease liabilities $ 5 $ 5 Right-of-use assets obtained in exchange for operating lease liabilities (non-cash) 1 — Supplemental balance sheet information related to leases is as follows: December 31, 2023 2022 Operating leases: Operating lease right of use assets $ 19 $ 21 Operating lease liabilities 22 25 Weighted average remaining lease term: Operating leases 6.1 years 6.8 years Weighted average discount rate: Operating leases 7.9 % 7.8 % Operating lease right of use assets and operating lease liabilities are included in Other assets and Other liabilities, respectively, on the consolidated balance sheet. Future undiscounted lease payments, gross of sublease receipts, to be made are as follows: As of December 31, 2023 Operating 2024 $ 4 2025 5 2026 5 2027 5 2028 5 Thereafter 5 Total lease payments 28 Less: imputed interest (6) Total $ 22 Lessor information Ambac is the lessor in one operating sublease of corporate office space which has a remaining term of 6.0 years. There are no extension or termination provisions. Future undiscounted lease payments to be received are as follows: As of December 31, 2023 Operating 2024 $ 1 2025 1 2026 1 2027 1 2028 1 Thereafter 1 Total lease receipts $ 8

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended	12 Months Ended
Commitments and Contingencies	Jun. 30, 2022	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	19. COMMITMENTS AND CONTINGENCIES	19. COMMITMENTS AND CONTINGENCIES Litigation Against Ambac - Pending Cases Monterey Bay Military Housing, LLC, et al. v. Ambac Assurance Corporation, et al. (United States District Court, Southern District of New York, Case No. 1:19-cv-09193-PGG, transferred on October 4, 2019 from the United States District Court, Northern District of California, San Jose Division, Case No. 17-cv-04992-BLF, filed August 28, 2017). Plaintiffs, the corporate developers of various military housing projects, filed an amended complaint on October 27, 2017 against AAC, a former employee of AAC, and certain unaffiliated persons and entities, asserting claims for (i) violation of 18 U.S.C §§ 1962(c) and 1962(d) (civil Racketeer Influenced and Corrupt Organizations Act (“RICO”) and conspiracy to commit civil RICO), (ii) breach of fiduciary duty, (iii) aiding and abetting breach of fiduciary duty, (iv) fraudulent misrepresentation, (v) fraudulent concealment and (vi) conspiracy to commit fraud. The claims relate to bonds and debt certificates (insured by AAC) that were issued to finance the renovation and construction of housing at certain military bases. Plaintiffs allege that defendants secretly conspired to overcharge plaintiffs for the financing of the projects and directed the excess profits to themselves. Plaintiffs allege defendants generated these excess profits by supposedly charging inflated interest rates, manipulating “shadow ratings,” charging unnecessary fees, and hiding evidence of their alleged wrongdoing. Plaintiffs seek, among other things, compensatory damages, disgorgement of profits and fees, punitive damages, trebled damages and attorneys’ fees. AAC and the other defendants filed motions to dismiss the amended complaint on November 13, 2017. On July 17, 2018, the court granted AAC’s and the other defendants’ motion to dismiss the first amended complaint without prejudice. On December 17, 2018, Plaintiffs filed a second amended complaint. On February 15, 2019, AAC and the other defendants filed a motion to dismiss the second amended complaint. On September 26, 2019, the court issued a decision denying defendants’ motion to dismiss and sua sponte reconsidering its previous denial of defendants’ motion to transfer venue to the Southern District of New York (“SDNY”). On October 10, 2019, after the case was transferred to the SDNY, the defendants filed motions to vacate or reconsider the decision by the Northern District of California on the defendants’ motion to dismiss. On March 31, 2021, the court granted defendants’ motions for reconsideration and, upon reconsideration, dismissed the claims against AAC and its former employee for breach of fiduciary duty and for aiding and abetting breach of AAC’s or its former employee’s fiduciary duty; dismissed two plaintiffs’ RICO claims against AAC and its former employee; and in all other respects denied defendants’ motions. Defendants served answers to the second amended complaint on April 21, 2021, asserting several affirmative defenses, including a defense for unclean hands focused on the plaintiffs’ failure to maintain the project properties and falsification of maintenance records. On May 24, 2021, plaintiffs moved to strike defendants’ unclean hands defenses. On September 14, 2021, Magistrate Judge Sarah L. Cave, to whom plaintiffs’ motion to strike was referred for a Report and Recommendation, issued an opinion and order denying plaintiffs’ motion. On April 6, 2022, certain co-defendants filed a motion to sever the plaintiffs’ claims and to dismiss all claims except for claims asserted by the Monterey Bay plaintiffs. On January 26, 2024, the Court granted the parties leave to file motions for summary judgment, with opening briefs due March 8, 2024, oppositions due April 19, 2024, and replies due May 10, 2024. In re National Collegiate Student Loan Trusts Litigation (Delaware Court of Chancery, Consolidated C.A. No. 12111, filed November 1, 2019). On November 1, 2019, AAC became aware of a new declaratory judgment action filed by certain residual equity interest holders (“NC Owners” or “Plaintiffs”) in fourteen National Collegiate Student Loan Trusts (the “Trusts”) against Wilmington Trust Company, the Owner Trustee for the Trusts; U.S. Bank National Association, the Indenture Trustee; GSS Data Services, Inc., the Administrator; and AAC. Through this action, Plaintiffs seek a number of judicial determinations. On January 21, 2020, the presiding Vice Chancellor entered an order consolidating the action with previously filed litigation relating to the Trusts. On February 13, 2020, AAC, the Owner Trustee, the Indenture Trustee, and other parties filed declaratory judgment counterclaims. Several parties, including Plaintiffs and AAC, filed motions for judgment on the pleadings in support of their requested judicial determinations. On August 27, 2020, the Vice Chancellor issued an opinion addressing all of the pending motions for judgment on the pleadings, which granted certain of the parties’ requested judicial determinations and denied others. He deferred judgment on still other declarations pending further factual development. The Vice Chancellor entered a series of stays to facilitate good-faith settlement discussions, the most recent of which was entered on May 2, 2023, and stayed the matter through May 5, 2023. On February 23, 2024, the parties filed a status report stating that they continue to negotiate a resolution to the various pending claims. Financial Oversight and Management Board for Puerto Rico, et al. v. Autonomy Master Fund Limited, et al. (United States District Court, District of Puerto Rico, No. 19-ap-00291, filed May 2, 2019). On May 2, 2019, the Financial Oversight and Management Board for Puerto Rico (the “Oversight Board”), together with the Official Committee of Unsecured Creditors for the Commonwealth (the “Committee”), filed an adversary proceeding against certain parties that filed proofs of claim on account of general obligation bonds issued by the Commonwealth of Puerto Rico, including AAC. The complaint seeks declarations that the general obligation bonds are unsecured obligations and, in the alternative, seeks to avoid any security interests that holders of such bonds may have. On June 12, 2019, a group of general obligation bondholders moved to dismiss the complaint. On June 13, 2019, at the request of the Plaintiffs, the District Court stayed the case until September 1, 2019 as to all defendants; on July 24, 2019, the District Court referred this matter to mediation and ordered it stayed during the pendency of such mediation. AAC filed a statement of position and reservation of rights on February 5, 2020; certain other defendants filed motions to dismiss on this same date. On February 9, 2020, the Oversight Board announced that it intended to file, and to seek to confirm, an amended plan of adjustment (the “Commonwealth Plan”). On March 10, 2020, the District Court ordered that this case remain stayed while the Oversight Board attempted to confirm the Commonwealth Plan. The January 18, 2022 confirmation of the Commonwealth Plan (described below) resolved this litigation. On May 9, 2022, the District Court dismissed this case. Financial Oversight and Management Board for Puerto Rico, et al. v. Ambac Assurance Corporation, et al. (United States District Court, District of Puerto Rico, No. 19-ap-00363, filed May 20, 2019). On May 20, 2019, the Oversight Board, together with the Committee, as Plaintiffs, filed an adversary proceeding against certain parties that filed proofs of claim on account of bonds issued by PRHTA (as defined below), including AAC. The complaint seeks declarations that the PRHTA bonds are only secured by revenues on deposit with the PRHTA fiscal agent and that PRHTA bondholders have no security interest in any other property of PRHTA or the Commonwealth, and in the alternative, to the extent such other security interests exist, the complaint seeks to avoid other security interests that holders of PRHTA bonds may have. On June 14, 2019, at the request of the Plaintiffs, the District Court stayed the case until September 1, 2019; on July 24, 2019, the District Court referred this matter to mediation and ordered it stayed during the pendency of such mediation. On December 19, 2019, the District Court ordered that this matter remain stayed pending further order of the District Court pursuant to the Oversight Board’s initiation of a separate adversary proceeding concerning PRHTA bonds (No. 20-ap-00005, discussed below). The October 12, 2022 confirmation of the PRHTA POA (as defined and described below) resolved this litigation. AAC expects this case will be dismissed pursuant to PRHTA POA. Financial Oversight and Management Board for Puerto Rico v. Ambac Assurance Corp., et al. (United States District Court, District of Puerto Rico, No. 20-ap-00003, filed Jan. 16, 2020). On January 16, 2020, the Oversight Board filed an adversary proceeding against monoline insurers insuring PRIFA (as defined below) bonds and the PRIFA bond trustee, all of which defendants filed proofs of claim against the Commonwealth relating to PRIFA bonds. The complaint seeks to disallow defendants’ proofs of claim against the Commonwealth in their entirety, including for lack of secured status. On February 27, 2020, defendants filed motions to dismiss. On March 10, 2020, the District Court stayed the motions to dismiss and authorized the Oversight Board to move for summary judgment, which motion defendants opposed. On May 5, 2021, Assured Guaranty Corp. and Assured Guaranty Municipal Corp. (“Assured”) and National Public Finance Guarantee Corporation (“National”) announced an agreement with the Oversight Board with respect to the PRHTA/PRCCDA Settlement (as defined below). On July 14, 2021, AAC and Financial Guaranty Insurance Company (“FGIC”) reached an agreement in principle with the Oversight Board with respect to the PRIFA Settlement (as defined below). On August 2, 2021, the Oversight Board, AAC, FGIC, and the PRIFA bond trustee jointly moved to stay this case as a result of the PRIFA Settlement and AAC’s joinder to the PRHTA/PRCCDA Settlement and the GO/PBA Settlement (as defined below). On August 3, 2021, the District Court ordered that this case be stayed. The January 18, 2022 confirmation of the Commonwealth Plan (described below) resolved this litigation. On September 30, 2022, the District Court entered an order closing this adversary proceeding. Financial Oversight and Management Board for Puerto Rico v. Ambac Assurance Corp., et al. (United States District Court, District of Puerto Rico, No. 20-ap-00004, filed Jan. 16, 2020). On January 16, 2020, the Oversight Board filed an adversary proceeding against monoline insurers insuring PRCCDA (as defined below) bonds and the PRCCDA bond trustee, all of which defendants filed proofs of claim against the Commonwealth relating to PRCCDA bonds. The complaint seeks to disallow defendants’ proofs of claim against the Commonwealth in their entirety, including for lack of secured status. On February 27, 2020, defendants filed motions to dismiss. On March 10, 2020, the District Court stayed the motions to dismiss and authorized the Oversight Board to move for summary judgment, which motion defendants opposed. On May 5, 2021, Assured and National announced an agreement with the Oversight Board with respect to the PRHTA/PRCCDA Settlement. On July 14, 2021, AAC and FGIC reached an agreement in principle with the Oversight Board with respect to the PRIFA Settlement. On August 2, 2021, the Oversight Board, AAC, FGIC, and the PRCCDA bond trustee jointly moved to stay this case as a result of the PRIFA Settlement and AAC’s joinder to the PRHTA/PRCCDA Settlement and the GO/PBA Settlement. On August 3, 2021, the District Court ordered that this case be stayed. The January 18, 2022 confirmation of the Commonwealth Plan (described below) resolved this litigation. On September 30, 2022, the Court entered an order closing this adversary proceeding. Financial Oversight and Management Board for Puerto Rico v. Ambac Assurance Corp., et al. (United States District Court, District of Puerto Rico, No. 20-ap-00005, filed Jan. 16, 2020). On January 16, 2020, the Oversight Board filed an adversary proceeding against monoline insurers insuring PRHTA bonds, certain PRHTA bondholders, and the PRHTA fiscal agent for bondholders, all of which defendants filed proofs of claim against the Commonwealth relating to PRHTA bonds. The complaint seeks to disallow defendants’ proofs of claim against the Commonwealth in their entirety, including for lack of secured status. On February 27, 2020, defendants filed motions to dismiss. On March 10, 2020, the District Court stayed the motions to dismiss and authorized the Oversight Board to move for summary judgment, which motion defendants opposed. On May 5, 2021, Assured and National announced an agreement with the Oversight Board with respect to the PRHTA/PRCCDA Settlement. On July 14, 2021, AAC and FGIC reached an agreement in principle with the Oversight Board with respect to the PRIFA Settlement. On August 2, 2021, the Oversight Board, AAC, FGIC, and the PRHTA fiscal agent jointly moved to stay this case as a result of the PRIFA Settlement and AAC’s joinder to the PRHTA/PRCCDA Settlement and the GO/PBA Settlement. On August 3, 2021, the District Court ordered that this case be stayed. The January 18, 2022 confirmation of the Commonwealth Plan (described below) resolved this litigation. On September 30, 2022, the District Court entered an order closing this adversary proceeding. Financial Oversight and Management Board for Puerto Rico v. Ambac Assurance Corp., et al. (United States District Court, District of Puerto Rico, No. 20-ap-00007, filed Jan. 16, 2020). On January 16, 2020, the Oversight Board and the Committee filed an adversary proceeding against monoline insurers insuring bonds issued by PRHTA, certain PRHTA bondholders, and the PRHTA fiscal agent for bondholders, all of which defendants filed proofs of claim against PRHTA relating to PRHTA bonds. The complaint seeks to disallow portions of defendants’ proofs of claim against PRHTA, including for lack of secured status. On March 10, 2020, the District Court stayed this case. On May 5, 2021, Assured and National announced an agreement with the Oversight Board with respect to the PRHTA/PRCCDA Settlement. On July 14, 2021, AAC and FGIC reached an agreement in principle with the Oversight Board with respect to the PRIFA Settlement. On August 2, 2021, the Oversight Board, AAC, FGIC, and the PRHTA fiscal agent jointly moved to stay this case as a result of the PRIFA Settlement and AAC’s joinder to the PRHTA/PRCCDA Settlement and the GO/PBA Settlement. On August 3, 2021, the District Court ordered that this case be stayed. On April 14, 2022, the Oversight Board filed a notice that this case has not been resolved by the Commonwealth Plan and should remain pending. The October 12, 2022 confirmation of the PRHTA POA (described below) resolved this litigation. On September 30, 2022, the Court entered an order closing this adversary proceeding. Litigation Against Ambac - General AAC’s estimates of projected losses for RMBS transactions consider, among other things, the RMBS transactions’ payment waterfall structure, including the application of interest and principal payments and recoveries, and depend in part on our interpretations of contracts and other bases of our legal rights. From time to time, bond trustees and other transaction participants have employed different contractual interpretations and have commenced, or threatened to commence, litigation to resolve these differences. It is not possible to predict whether additional disputes will arise, nor the outcomes of any potential litigation. It is possible that there could be unfavorable outcomes in this or other disputes or proceedings and that our interpretations may prove to be incorrect, which could lead to changes to our estimate of loss reserves. The Company periodically receives various regulatory inquiries and requests for information with respect to investigations and inquiries that such regulators are conducting. The Company has complied with all such inquiries and requests for information. The Company is involved from time to time in various routine legal proceedings, including proceedings related to litigation with present or former employees. Although such litigation routine and incidental to the conduct of its business, such litigation can potentially result in large monetary awards when a civil jury is allowed to determine compensatory and/or punitive damages. Everspan may be subject to disputes with policyholders regarding the scope and extent of coverage offered under Everspan's policies; be required to defend claimants in suits against its policyholders for covered liability claims; or enter into commercial disputes with its reinsurers, MGA/Us or third party claims administrators regarding their respective contractual obligations and rights. Under some circumstances, the results of such disputes or suits may lead to liabilities beyond those which are anticipated or reserved. From time to time, Ambac is subject to allegations concerning its corporate governance that may lead to litigation, including derivative litigation, and while the monetary impacts may not be material, the matters may distract management and the Board of Directors from their principal focus on Ambac's business, strategy and objectives. It is not reasonably possible to predict whether additional suits will be filed or whether additional inquiries or requests for information will be made, and it is also not possible to predict the outcome of litigation, inquiries or requests for information. It is possible that there could be unfavorable outcomes in these or other proceedings. Legal accruals for litigation against the Company with losses that are probable and reasonably estimable are not material to the operating results or financial position of the Company. For the litigation matters the Company is defending that do not meet the “probable and reasonably estimable” accrual threshold and where no loss estimates have been provided above, management is unable to make a meaningful estimate of the amount or range of loss that could result from unfavorable outcomes. Under some circumstances, adverse results in any such proceedings could be material to our business, operations, financial position, profitability or cash flows. The Company believes that it has substantial defenses to the claims above and, to the extent that these actions proceed, the Company intends to defend itself vigorously; however, the Company is not able to predict the outcomes of these actions. Litigation Filed or Joined by Ambac In the ordinary course of their businesses, certain of Ambac’s subsidiaries assert claims in legal proceedings against third parties to recover losses already paid and/or mitigate future losses. The amounts recovered and/or losses avoided which may result from these proceedings is uncertain, although recoveries and/or losses avoided in any one or more of these proceedings during any quarter or fiscal year could be material to Ambac’s results of operations in that quarter or fiscal year. Puerto Rico On January 18, 2022, the United States District Court for the District of Puerto Rico (the “District Court”) entered an order confirming a plan of adjustment for the Commonwealth of Puerto Rico (the “Commonwealth Plan”). On January 20, 2022, the District Court entered orders approving a Qualifying Modification (the “PRIFA QM”) for the Puerto Rico Infrastructure Finance Authority (“PRIFA”) and a Qualifying Modification (the “PRCCDA QM”) for the Puerto Rico Convention Center District Authority (“PRCCDA”). On October 12, 2022, the District Court entered an order confirming a plan of adjustment (the “PRHTA POA”) for the Puerto Rico Highways and Transportation Authority (the “PRHTA”). These two plans of adjustment and two qualifying modifications incorporated settlements reached between AAC, the Oversight Board, and certain other parties related to each of AAC’s Puerto Rico-related exposures, which included agreements with respect to the treatment of general obligation and Puerto Rico Public Buildings Authority (“PBA”) bonds (the “GO/PBA Settlement”), PRHTA and PRCCDA bonds (the “PRHTA/PRCCDA Settlement”), and PRIFA bonds (the “PRIFA Settlement”). By incorporating these settlements, the Commonwealth Plan, PRIFA QM, PRCCDA QM, and PRHTA POA resolved the majority of AAC’s outstanding Puerto Rico-related litigation. Certain parties appealed the confirmation orders for both the Commonwealth Plan and the PRHTA POA; all of these appeals have been resolved and the orders confirming both plans were affirmed. Those appeals are discussed immediately below, followed by a discussion of AAC’s additional remaining outstanding Puerto Rico-related litigation. In re Financial Oversight and Management Board for Puerto Rico (United States District Court, District of Puerto Rico, No. 1:17- bk-03283) (appeals of the Commonwealth Plan). On January 18, 2022, the District Court entered an order confirming the Commonwealth Plan and entered its findings of fact and conclusions of law related thereto. Several parties appealed the District Court’s confirmation order to the First Circuit Court of Appeals, but the First Circuit affirmed the District Court in all appeals and all appeals have been dismissed. In re Financial Oversight and Management Board for Puerto Rico (United States District Court, District of Puerto Rico, No. 1:17- bk-03567) (appeal of the PRHTA POA). On October 12, 2022, the District Court entered an order confirming the PRHTA POA and entered its findings of fact and conclusions of law related thereto. On October 24, 2022, a group of present and former employees of PRHTA (“the Vazquez-Velazquez Group”) filed a notice of appeal with respect to, and a motion to stay, the PRHTA POA confirmation order. One party appealed the District Court’s confirmation order to the First Circuit Court of Appeals, but the First Circuit affirmed the District Court and the appeal has been dismissed. Assured Guaranty Corp., Assured Guaranty Municipal Corp., and Ambac Assurance Corporation v. Alejandro Garcia Padilla, et al. (United States District Court, District of Puerto Rico No. 3:16-cv-01037, filed January 7, 2016). On January 7, 2016, AAC, along with co-plaintiffs Assured, filed a complaint for declaratory and injunctive relief to protect its rights against the illegal clawback of certain revenue by the Commonwealth of Puerto Rico. Defendants moved to dismiss on January 29, 2016. On October 4, 2016, the court denied the Defendants’ motions to dismiss. On October 14, 2016, Defendants filed a Notice of Automatic Stay, asserting that Plaintiffs’ claims have been rendered moot and further asserting that the case was automatically stayed under section 405 of the Puerto Rico Oversight, Management and Economic Stability Act ("PROMESA"). On May 3, 2017, the Oversight Board filed a petition to adjust the Commonwealth’s debts under Title III of PROMESA, resulting in an automatic stay of litigation against the Commonwealth. On May 17, 2017, the court issued an order staying this case until further order of the court. AAC expects this case will be dismissed given the settlements reached between AAC and the Oversight Board. Ambac Assurance Corporation v. Puerto Rico Highways and Transportation Authority (United States District Court, District of Puerto Rico, No. 16-cv-1893, filed May 10, 2016). AAC filed a complaint against the PRHTA on May 10, 2016, alleging breach of fiduciary duty and breach of contract in connection with PRHTA’s extension of an existing toll road concession agreement. The complaint alleges that it was inappropriate for PRHTA to enter into the extension agreement in its current state of financial distress because PRHTA has no control over, and is unlikely to receive, the proceeds of the transaction. AAC also filed related motions seeking the appointment of a provisional receiver for PRHTA and expedited discovery. On May 21, 2017, the Oversight Board filed a petition to adjust PRHTA’s debts under Title III of PROMESA, resulting in an automatic stay of litigation against PRHTA. On May 24, 2017, the court issued an order staying this case until further order of the court. The settlements reached between AAC and the Oversight Board resolved this litigation, and the January 20, 2022 PRIFA QM provided for dismissal of this case. AAC expects this case will be dismissed pursuant to the PRIFA QM. Ambac Assurance Corporation v. Bank of New York Mellon (United States District Court, Southern District of New York, No. 1:17-cv-03804, filed May 2, 2017). On May 2, 2017, AAC filed a complaint in New York State Supreme Court, New York County, against the trustee for the COFINA bonds, Bank of New York Mellon (“BNY”), alleging breach of fiduciary, contractual, and other duties for failing to adequately and appropriately protect the holders of certain AAC-insured senior COFINA bonds. On May 19, 2017, BNY filed a notice of removal of this action from New York state court to the United States District Court for the Southern District of New York. On May 30, 2017, the United States District Court for the District of Puerto Rico entered an order in an adversary proceeding brought by BNY (No. 1:17-ap-00133) staying this litigation pending further order of the court. The COFINA Plan became effective on February 12, 2019, and, pursuant to the District Court’s confirmation order, this litigation was permitted to continue, with AAC’s claims against BNYM being limited to those for gross negligence, willful misconduct and intentional fraud. On November 17, 2021, the District Court denied as moot BNY's motion to transfer venue to the District of Puerto Rico and continued the stay of the action. On July 6, 2022, the District Court granted AAC’s motion to lift the stay and for leave to file a Second Amended Complaint (“SAC”). AAC filed its SAC on July 10, 2022, and on July 25, 2022, BNY moved to dismiss the SAC. On September 23, 2022, Ambac filed its opposition to BNY’s motion to dismiss, and on October 24, 2022, BNY filed its reply in support of its motion to dismiss. Oral argument has been requested but not yet scheduled. Financial Oversight and Management Board for Puerto Rico v. Public Buildings Authority (United States District Court, District of Puerto Rico, No. 1:18-ap-00149, filed December 21, 2018). On December 21, 2018, the Oversight Board, together with the Committee, as Plaintiffs, filed a complaint against the PBA seeking declaratory judgment that the leases between PBA and its lessees—many of whom are agencies and instrumentalities of the Commonwealth—are “disguised financings,” not true leases, and therefore should not be afforded administrative expense priority under the Bankruptcy Code. On March 12, 2019, AAC and other interested parties were permitted to intervene in order to argue that the PBA leases are valid leases and are entitled to administrative expense treatment under the Bankruptcy Code. On March 10, 2020, the District Court ordered that this case be stayed while the Oversight Board attempted to confirm the Commonwealth Plan. The January 18, 2022 confirmation of the Commonwealth Plan resolved this litigation. In re Financial Oversight and Management Board for Puerto Rico (United States District Court, District of Puerto Rico, No. 1:17-bk-03283), Omnibus Objection of (I) Financial Oversight and Management Board, Acting Through its Special Claims Committee, and (II) Official Committee of Unsecured Creditors, Pursuant to Bankruptcy Code Section 502 and Bankruptcy Rule 3007, to Claims Filed or Asserted by Holders of Certain Commonwealth General Obligation Bonds (Dkt. No. 4784, filed January 14, 2019) (“GO Bond Claim Objection”). On January 14, 2019, the Oversight Board and the Committee filed an omnibus claim objection in the Commonwealth’s Title III case challenging claims arising from certain general obligation bonds issued by the Commonwealth in 2012 and 2014 totaling approximately $6 billion, none of which are held or insured by AAC. On April 11, 2019, AAC filed a notice of participation in support of the objection, advancing the argument, among other things, that the PBA leases are true leases, but the associated debt nonetheless should be included in the Commonwealth’s debt ceiling calculation such that the 2012 and 2014 general obligation bond issuances are null and void and claims arising therefrom should be disallowed. On February 5 and 19, 2020, certain parties filed motions to dismiss the claim objection. On March 10, 2020, the District Court ordered that this matter remain stayed while the Oversight Board attempted to confirm the Commonwealth Plan. On July 19, 2020, the Committee filed a motion to lift the stay on this claim objection in light of changes to the Commonwealth’s fiscal plan and likely changes to the Commonwealth Plan in light of COVID-19. On September 1, 2020, AAC filed a partial joinder to the Committee’s motion. On September 17, 2020, the District Court denied the Committee’s motion without prejudice. On October 1, 2020, the Committee moved the District Court to reconsider its denial of the Committee’s motion to lift the stay; on October 5, 2020, the District Court denied the Committee’s motion for reconsideration. On October 16, 2020, the Committee appealed to the First Circuit the District Court’s order denying the Committee’s motion to lift the stay on its claim objection. On February 22, 2021, the First Circuit dismissed the appeal. The January 18, 2022 confirmation of the Commonwealth Plan resolved this litigation. On September 30, 2022, the Court entered an order terminating this matter. In re Financial Oversight and Management Board for Puerto Rico (United States District Court, District of Puerto Rico, No. 1:17-bk-03283), Ambac Assurance Corporation's Motion and Memorandum of Law in Support of Its Motion Concerning Application of the Automatic Stay to the Revenues Securing PRIFA Rum Tax Bonds (Dkt. No. 7176, filed May 30, 2019) (“PRIFA Stay Motion”). On May 30, 2019, AAC and FGIC filed a motion seeking an order that the automatic stay does not apply to certain lawsuits AAC seeks to bring or to continue relating to bonds issued by PRIFA, or, in the alternative, for relief from the automatic stay to pursue such lawsuits or for adequate protection of AAC's collateral. On January 31, 2020, AAC, FGIC, Assured, and the PRIFA bond trustee filed an amended motion seeking substantially similar relief. On July 2, 2020, the District Court denied the motion to lift the stay on certain grounds. Briefing regarding additional grounds on which AAC and other movants seek stay relief concluded on August 5, 2020; on September 9, 2020, the District Court denied the motion to lift the stay on the additional grounds. On September 23, 2020, AAC and the other movants appealed this decision to the First Circuit. On March 3, 2021, the First Circuit affirmed the District Court’s opinions denying the motion to lift the stay. On May 5, 2021, Assured and National announced an agreement with the Oversight Board with respect to the PRHTA/PRCCDA Settlement. On July 14, 2021, AAC and FGIC reached an agreement in principle with the Oversight Board with respect to the PRIFA Settlement, and as a result of that settlement, also joined the PRHTA/PRCCDA Settlement. On August 2, 2021, the Oversight Board, AAC, FGIC, and the PRIFA bond trustee jointly moved to stay this motion as a result of the PRIFA Settlement and AAC’s joinder to the PRHTA/PRCCDA Settlement and the GO/PBA Settlement. On August 3, 2021, the District Court ordered that this motion be stayed. The January 18, 2022 confirmation of the Commonwealth Plan resolved this litigation. In re Financial Oversight and Management Board for Puerto Rico (United States District Court, District of Puerto Rico, No. 1:17-bk-03283), Motion of Assured Guaranty Corp., Assured Municipal Corp., Ambac Assurance Corporation, National Public Finance Guarantee Corporation, and Financial Guaranty Insurance Company for Relief from the Automatic Stay, or, in the Alternative, Adequate Protection (Dkt. No. 10102, filed January 16, 2020) (“PRHTA Stay Motion”). On January 16, 2020, AAC, Assured, National, and FGIC filed a motion seeking an order that the automatic stay does not apply to movants’ enforcement of the application of pledged revenues to the PRHTA bonds or the enforcement of movants’ liens on revenues pledged to such bonds, or, in the alter

SEC Schedule, Article 12-04, Co

SEC Schedule, Article 12-04, Condensed Financial Information of Registrant	12 Months Ended
	Dec. 31, 2023
Condensed Financial Information Disclosure [Abstract]
Condensed Financial Information of Parent Company Only Disclosure	AMBAC FINANCIAL GROUP, INC. AND SUBSIDIARIES Condensed Financial Information Of Registrant (Parent Company Only) Condensed Balance Sheets ($ in millions, except share data) December 31, 2023 2022 Assets: Fixed maturity securities, at fair value (amortized cost of $14 and $13) $ 14 $ 12 Short-term investments, at fair value (amortized cost of $156 and $175) 156 175 Other investments 18 16 Total investments (net of allowance for credit losses of $0 and $0) 188 203 Cash — 3 Investment in subsidiaries 1,150 1,029 Investment income due and accrued 1 1 Other assets 24 19 Total assets $ 1,365 $ 1,255 Liabilities and Stockholders' Equity: Liabilities: Current taxes $ — $ 1 Accounts payable and other liabilities 3 3 Total liabilities 4 3 Stockholders’ equity: Preferred stock, par value $0.01 per share; 20,000,000 shares authorized shares; issued and outstanding shares—none — — Common stock, par value $0.01 per share; 130,000,000 shares authorized; issued shares: 46,659,144 and 46,658,990 — — Additional paid-in capital 292 274 Accumulated other comprehensive income (loss) (160) (253) Retained earnings 1,246 1,245 Treasury stock, shares at cost: 1,463,774 and 1,685,233 (17) (15) Total Ambac Financial Group, Inc. stockholders’ equity 1,362 1,252 Total liabilities and stockholders’ equity $ 1,365 $ 1,255 The condensed financial statements should be read in conjunction with the consolidated financial statements and notes thereto and the following notes. See the Report of Independent Registered Public Accounting Firm. SCHEDULE II AMBAC FINANCIAL GROUP, INC. AND SUBSIDIARIES Condensed Financial Information Of Registrant (Parent Company Only) Condensed Statement of Comprehensive Income ($ in millions) Year Ended December 31, 2023 2022 2021 Revenues: Investment income $ 9 $ 10 $ 10 Other income — — — Net gains on derivative contracts — 1 — Net investment gains (losses), including impairments — (14) (5) Total revenues 9 (2) 5 Expenses: General and administrative expenses 22 17 19 Total expenses 22 17 19 Income (loss) before income taxes and net income (loss) of subsidiaries (13) (20) (14) Federal income tax provision (benefit) (1) — 2 Income (loss) before net income (loss) of subsidiaries (11) (19) (16) Net income (loss) of subsidiaries 15 542 (1) Net income (loss) $ 4 $ 522 $ (17) Other comprehensive income (loss), after tax: Net income (loss) $ 4 $ 522 $ (17) Unrealized gains (losses) on securities, net of income tax provision (benefit) of $2, $(6) and $(2) 51 (225) (12) Gains (losses) on foreign currency translation, net of income tax provision (benefit) of $—, $— and $— 40 (85) (8) Credit risk changes of fair value option liabilities, net of income tax provision (benefit) of $—, $— and $— — — (1) Changes to postretirement benefit, net of income tax provision (benefit) of $—, $— and $— 2 (1) (1) Total other comprehensive income (loss) 93 (310) (21) Total comprehensive income (loss) attributable to Ambac Financial Group, Inc. $ 96 $ 212 $ (38) The condensed financial statements should be read in conjunction with the consolidated financial statements and notes thereto and the following notes. See the Report of Independent Registered Public Accounting Firm. SCHEDULE II AMBAC FINANCIAL GROUP, INC. AND SUBSIDIARIES Condensed Financial Information Of Registrant (Parent Company Only) Condensed Statement of Stockholders' Equity ($ in millions) Total Preferred Stock Common Stock Additional Paid-in Capital Accumulated Other Comprehensive Income (Loss) Retained Earnings Common Stock Held in Treasury, at Cost Balance at January 1, 2021 $ 1,080 $ — $ — $ 242 $ 79 $ 759 $ (1) Total comprehensive income (loss) (38) — — — (21) (17) — Adjustment to initially apply ASU 2016-13 — — — — — — — Stock-based compensation 14 — — 14 — — — Cost of shares (acquired) issued under equity plan (6) — — — — (4) (2) Balance at December 31, 2021 1,038 — — 257 58 726 (3) Total comprehensive income (loss) 211 — — — (310) 521 — Stock-based compensation 17 — — 17 — — — Cost of shares (acquired) issued under equity plan (4) — — — — (5) 2 Cost of shares repurchased (14) — — — — — (14) Changes to redeemable noncontrolling interest 3 — — — — 3 — Purchase of Ambac Assurance auction market preferred shares 1 — — — — 1 — Balance at December 31, 2022 1,252 — — 274 (253) 1,245 (15) Total comprehensive income (loss) 96 — — — 93 4 — Stock-based compensation 17 — — 17 — — — Cost of shares (acquired) issued under equity plan (5) — — — — (8) 3 Cost of shares repurchased (5) — — — — — (5) Change in redeemable noncontrolling interest 5 — — — — 5 — Balance at December 31, 2023 $ 1,362 $ — $ — $ 292 $ (160) $ 1,246 $ (17) The condensed financial statements should be read in conjunction with the consolidated financial statements and notes thereto and the following notes. See the Report of Independent Registered Public Accounting Firm. SCHEDULE II AMBAC FINANCIAL GROUP, INC. AND SUBSIDIARIES Condensed Financial Information Of Registrant (Parent Company Only) Condensed Statements of Cash Flow ($ in millions) Year Ended December 31, 2023 2022 2021 Cash flows from operating activities: Net income (loss) $ 4 $ 522 $ (17) Adjustments to reconcile net income loss to net cash used in operating activities: Net (income) loss of subsidiaries (15) (542) 1 Amortization of bond premium and discount — (7) (9) Net investment gains (losses), including impairments — 14 5 Increase (decrease) in current income taxes payable (2) (1) 1 Share-based compensation 9 12 14 (Increase) decrease in other assets and liabilities (5) 41 (5) Distributions received from majority owned subsidiary 8 6 6 Other, net 2 1 (6) Net cash provided by (used in) operating activities 2 46 (10) Cash flows from investing activities: Proceeds from sales and matured bonds — 68 33 Purchases of bonds (1) (1) (34) Change in short-term investments 20 (51) 105 Change in other investments (3) (4) (8) Net cash provided by (used in) investing activities 16 12 95 Cash flows from financing activities: Capital contribution to subsidiaries (16) (42) (92) Cost of shares acquired (5) (14) — Net cash (used in) financing activities (21) (57) (92) Net cash flow (2) 1 (6) Cash at beginning of period 3 1 7 Cash at end of period $ — $ 3 $ 1 Supplemental disclosure of cash flow information: Cash paid during the period for: Income taxes $ — $ — $ — The condensed financial statements should be read in conjunction with the consolidated financial statements and notes thereto and the following notes.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss) Attributable to Parent	$ 4	$ 522	$ (17)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Reorganizations (Policies)

Reorganizations (Policies)	12 Months Ended
Reorganizations (Policies)	Dec. 31, 2023
Reorganizations [Abstract]
Strategies to Enhance Shareholder Vakye	Strategies to Enhance Shareholder Value The Company's primary goal is to maximize long-term shareholder value through the execution of targeted strategies for its (i) Specialty Property and Casualty Insurance and Insurance Distribution businesses and (ii) Legacy Financial Guarantee Insurance business. Specialty Property and Casualty Insurance and Insurance Distribution strategic priorities include: • Growing our Specialty Property and Casualty Insurance business to generate underwriting profits from a diversified portfolio of commercial and personal liability risks accessed primarily through program administrators. • Expanding our Insurance Distribution business based on deep domain knowledge in specialty and niche classes of risk which generate attractive margins at scale. This will be achieved through acquisitions, establishing new businesses “de-novo,” and organic growth and diversification supported by a centralized technology led shared services offering. • Making opportunistic investments that are strategic to both the Specialty Property and Casualty Insurance and Insurance Distribution businesses. Legacy Financial Guarantee Insurance strategic priorities include: • Actively managing, de-risking and mitigating insured portfolio risk, and pursuing recoveries of previously paid losses. • Improving operating efficiency and optimizing our asset and liability profile. • Exploring strategic options to further maximize value for AFG. The execution of Ambac’s strategy to increase the value of its investment in AAC is subject to the restrictions set forth in the Settlement Agreement, dated as of June 7, 2010, as amended (the "Settlement Agreement"), by and among AAC, Ambac Credit Products LLC ("ACP"), AFG and certain counterparties to credit default swaps with ACP that were guaranteed by AAC, as well as the Stipulation and Order among the OCI, AFG and AAC that became effective on February 22, 2024 (the “Stipulation and Order”), replacing the Stipulation and Order that became effective on February 12, 2018, as amended (the "2018 Stipulation and Order"), each of which requires OCI and, under certain circumstances contemplated by the Settlement Agreement, holders of surplus notes, to approve certain actions taken by or in respect of AAC. In exercising its approval rights, OCI will act for the benefit of policyholders, and will not take into account the interests of AFG. The Settlement Agreement limits certain activities of AAC and its subsidiaries, such as issuing indebtedness; engaging in mergers and similar transactions; disposing of assets; making restricted payments; creating or permitting liens; engaging in transactions with affiliates; modifying or creating tax sharing agreements; and taking certain actions with respect to surplus notes (among other restrictions and limitations). The Settlement Agreement includes certain allowances with respect to these activities and generally requires the approval of OCI and, in some cases, holders of surplus notes issued pursuant to the Settlement Agreement, for consents, waivers or amendments. The Stipulation and Order requires AAC to maintain a level of surplus and contingency reserves as regards policyholders which provide reasonable security against contingencies affecting AAC’s financial position that are not otherwise fully covered by reserves or reinsurance; discount loss reserves in a manner approved by OCI; maintain OCI’s Runoff Capital Framework according to parameters specified by OCI; pay the costs of consultants and other experts retained by OCI; limit affiliate transactions and the payment of any dividend or other distribution without the prior non-disapproval of OCI; notify OCI of events that would or would be reasonably likely to cause a material adverse effect to AAC or its affiliates; obtain OCI’s non-disapproval to exercise certain control rights with respect to certain policies that were previously allocated to the Segregated Account of AAC; obtain OCI’s approval for non-ordinary course transactions involving consideration to be paid by AAC of $100 or more; and obtain OCI’s approval of any changes to AAC’s investment policy or derivative use plan. The Stipulation and Order also requires AFG to use its best efforts to preserve the use of NOLs for the benefit of AAC and its subsidiaries. The Stipulation and Order differs from the 2018 Stipulation and Order in that the 2018 Stipulation and Order (i) did not refer to OCI’s Runoff Capital Framework; (ii) included certain affirmative covenants concerning books and records, and reporting of information or events, that were not included in the Stipulation and Order; and (iii) contained a more restrictive limitation on transactions with affiliates. The Stipulation and Order has no fixed term and may be terminated or modified only with the approval of OCI. OCI reserved the right to modify or terminate the Stipulation and Order in a manner consistent with the interests of policyholders, creditors and the public generally. The execution of Ambac’s strategy to increase the value of its investment in AAC may be affected by a new capital framework developed and implemented by OCI to assist OCI with making decisions related to capital management at AAC ("OCI's Runoff Capital Framework"). OCI’s Runoff Capital Framework applies risk-based and other adjustments to AAC’s assets and insured liabilities, as determined by OCI in its sole discretion. OCI’s Runoff Capital Framework allows AAC to understand the likely impact of various developments and actions now or in the future on AAC’s capital position thereunder. No changes in AAC’s current management of the business are required by OCI’s Runoff Capital Framework. AAC’s ability to use capital for potential future deleveraging transactions or distributions will require AAC to sustain an excess of risk-adjusted assets over risk-adjusted insured liabilities according to OCI’s Runoff Capital Framework, and to obtain OCI’s approval, and there can be no assurance that OCI will approve any such use of capital. The results of OCI’s Runoff Capital Framework are expected to vary over time based on changes in AAC’s financial position, insured portfolio developments, the impact of strategic actions taken by AAC, the impact of asset/liability management by AAC and, possibly, changes to the inputs and assumptions utilized by OCI. Opportunities for remediating losses on poorly performing insured transactions depend on market conditions, including the perception of AAC’s creditworthiness, the structure of the underlying risk and associated policy as well as other counterparty specific factors. AAC's ability to commute policies or purchase certain investments may also be limited by available liquidity.
Settlement of RMBS Litigation and Redemption of Secured Notes	Settlement of RMBS Litigations and Redemption of Secured Notes: In October 2022, AAC entered into a Settlement Agreement and Release (the “BOA Settlement Agreement”) with Bank of America Corporation and certain affiliates thereof (together, the “BOA Parties”) pursuant to which the BOA Parties paid AAC the sum of $1,840 (the “BOA Settlement Payment”) following the dismissal of AAC’s lawsuits against the BOA Parties concerning certain residential mortgage-backed securities (“RMBS”) trusts, and the withdrawal by AAC of its objections, including any pending appeals, concerning the settlements that were the subject of certain trust instructional proceedings. In exchange for the BOA Settlement Payment, AAC, on its own behalf and on behalf of its affiliates, agreed to release the BOA Parties and related parties (the “Released Parties”) from claims asserted or which could have been asserted in AAC’s pending litigations against the BOA Parties as well as claims that AAC and its affiliates ever had, may currently have or may have in the future against the Released Parties, subject to certain limited exceptions. The BOA Settlement Agreement also requires AAC to dismiss other pending claims against the Released Parties, and to generally refrain from, and in certain situations hold the Released Parties harmless with respect to, certain actions taken by AAC with respect to RMBS trusts created prior to the date of the BOA Settlement Agreement involving the Released Parties. The BOA Settlement Payment included recoveries from litigations for alleged breaches of contractual obligations and fraud by the BOA Parties. Management allocated the BOA Settlement Payment to each of the litigations based on previously developed valuations of each individual litigation. The portion of the BOA Settlement Payment allocated to fraud litigation recoveries has been recorded as a litigation recovery in the Statement of Comprehensive Income (Loss). On December 29, 2022, AAC entered into a Settlement Agreement and Release (the “Nomura Settlement Agreement”) with Nomura Credit & Capital, Inc. (“Nomura”) to settle its litigation against Nomura concerning certain RMBS trusts (the “Trusts”). Pursuant to the Nomura Settlement Agreement, Nomura made a cash payment to AAC of $140 (the "Nomura Settlement Payment"), and AAC and Nomura agreed to release each other and their respective affiliates and related persons from any claims relating to the Trusts, the financial guaranty policies issued by AAC in connection with Trusts (other than AAC’s obligations to pay insurance claims under such policies), the securities related to the Trusts, and the mortgage loans related to the Trusts. The Nomura Settlement Payment received in January 2023 reduced the subrogation recoverable asset on the Consolidated Balance Sheet. During 2022 and 2023, AAC wholly redeemed its secured debt, in accordance with the terms of such debt, utilizing the BOA Settlement Payment, the Nomura Settlement Payment and other resources as further discussed in Note 12. Long-term Debt . Impact to the Consolidated Statement of Comprehensive Income (Loss): The total gain recognized in net income attributable to common stockholders related to entering into the BOA Settlement Agreement and the Nomura Settlement Agreement, including the redemption of the Sitka AAC Note following receipt of the BOA Settlement Payment, was as follows: Year Ended December 31, 2022 Losses and loss benefit (1) $ 362 Litigation recoveries 126 Net realized gains (losses) on extinguishment of debt (53) Net investment gains (losses), including impairments 5 Impact to net income attributable to common stockholders $ 440 (1) 2022 losses and loss benefit relating to R&W recoveries were $123.

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating Leased Assets [Line Items]
Consolidation	Consolidation The consolidated financial statements include the accounts of AFG and all other entities in which AFG (directly or through its subsidiaries) has a controlling financial interest, including variable interest entities (“VIEs”) for which AFG or an AFG subsidiary is deemed the primary beneficiary in accordance with the Consolidation Topic of the Accounting Standards Codification ("ASC"). All significant intercompany balances have been eliminated. The usual condition for a controlling financial interest is ownership of a majority of the voting interests of an entity. However, a controlling financial interest may also exist in entities, such as VIEs, through arrangements that do not involve controlling voting interests. A VIE is an entity: a) that lacks enough equity investment at risk to permit the entity to finance its activities without additional subordinated financial support from other parties; or b) where the group of equity holders does not have: (1) the power, through voting rights or similar rights, to direct the activities of an entity that most significantly impact the entity’s economic performance; (2) the obligation to absorb the entity’s expected losses; or (3) the right to receive the entity’s expected residual returns. The determination of whether a variable interest holder is the primary beneficiary involves performing a qualitative analysis of the VIE that includes, among other factors, its capital structure, contractual terms including the rights of each variable interest holder, the activities of the VIE, whether the variable interest holder has the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance, whether the variable interest holder has the obligation to absorb losses of the VIE that could potentially be significant to the VIE or the right to receive benefits from the VIE that could potentially be significant to the VIE, related party relationships and the design of the VIE. An entity that is deemed the primary beneficiary of a VIE is required to consolidate the VIE. See Note 11. Variable Interest Entities
Unconsolidated Financial Information	AFG Unconsolidated Financial Information
Financing Receivable, Allowance for Credit Losses, Policy for Uncollectible Amounts	Measurement of Credit Losses on Financial Instruments (CECL) Ambac measures credit losses on financial assets that are not accounted for at fair value through net income in accordance with the Current Expected Credit Loss standard or "CECL". • The CECL impact on available-for-sale debt securities is discussed in the Investments sub-section below. • The CECL impact on amortized cost assets, including contract assets and receivables accounted for under the ASC 606 revenue recognition standard, is addressed in the Premiums, Reinsurance Recoverables, Loans and Revenue Recognition sub-sections below. These amortized cost assets reflect management's current estimate of all expected lifetime credit losses. The estimate of expected lifetime credit losses considers historical information, current information, as well as reasonable and supportable forecasts. Expected lifetime credit losses for amortized cost assets are recorded as an allowance for credit losses, with subsequent increases or decreases in the allowance reflected in net income each period.
Investments	Investments The Investments - Debt Securities Topic of the ASC requires that all debt instruments be classified in Ambac’s Consolidated Balance Sheets according to their purpose and, depending on that classification, be carried at either cost or fair market value. Ambac’s non-VIE debt investment portfolio is accounted for on a trade-date basis and consists primarily of: • Investments in fixed maturity securities are either classified as available-for-sale or trading as defined by the Investments - Debt Securities Topic of the ASC. Available-for-sale debt securities are reported in the financial statements at fair value with unrealized gains and losses, net of deferred taxes, reflected in Accumulated Other Comprehensive Income (Loss) in Stockholders’ Equity and computed using amortized cost as the basis. For purposes of computing amortized cost, premiums and discounts are accounted for using the effective interest method over the term of the security. For structured debt securities with a large underlying pool of homogenous loans, such as mortgage-backed and asset-backed securities, premiums and discounts are adjusted for the effects of actual and anticipated prepayments. For other fixed maturity securities, such as corporate and municipal bonds, discounts are amortized or accreted over the remaining term of the securities and premiums are amortized to the earliest call date. Investments in fixed maturity securities classified at trading are reported in the financial statements at fair value with unrealized gains and losses included in Net investment income on the Statement of Total Comprehensive Income (Loss). • Equity interests in pooled investment funds which are accounted for in accordance with the Investments - Equity Securities Topic of the ASC and reported as Other investments on the Consolidated Balance Sheet with income reported through Net investment income on the Statement of Total Comprehensive Income (Loss). Equity interests in the form of common stock or in-substance common stock are classified as trading securities and reported at fair value while limited partner interests in such funds are reported using the equity method. • Preferred equity investments that do not have readily determinable fair values and are carried at cost, less any impairments as permitted under the Investments — Equity Securities Topic of the ASC. VIE investments in fixed maturity securities are carried at fair value as they are classified as either available-for-sale or trading as defined by the Investments — Debt Securities Topic of the ASC, or accounted for under the fair value option election. For additional information about VIE investments, including fair value by asset-type, see Note 11. Variable Interest Entities . Fair value is based primarily on quotes obtained from independent market sources. When quotes for fixed maturity securities are not available or cannot be reasonably corroborated, valuation models are used to estimate fair value. These models include estimates, made by management, which utilize current market information. When fair value is not readily determinable for pooled investment funds, the investments are valued using net asset value ("NAV") as a practical expedient as permitted under the Fair Value Measurement Topic of the ASC. Investment valuations could differ materially from amounts that would actually be realized in the market. Realized gains and losses on the sale of investments are determined on the basis of specific identification. Refer to Note 5. Fair Value Measurements for further description of the methodologies used to determine the fair value of investments, including model inputs and assumptions where applicable. Ambac has a formal impairment review process for fixed maturity available-for-sale securities in its investment portfolio. Ambac conducts a review each quarter to identify and evaluate investments that have indications of impairment in accordance with the Investments - Debt Securities Topic of the ASC. If management either: (i) has the intent to sell its investment in an impaired debt security or (ii) determines that the Company more likely than not will be required to sell the debt security before its anticipated recovery of the amortized cost basis less any current period credit impairment, then an impairment charge is recognized in earnings, with the amortized cost of the security written-down to fair value. If management does not intend to sell, or will not be required to sell the debt security, the security is reviewed for credit impairment. Factors considered to identify and assess securities for credit impairment include: (i) fair values that have declined by 20% or more below amortized cost; (ii) recent downgrades by rating agencies; (iii) the financial condition of the issuer and financial guarantor, as applicable, and an analysis of projected defaults on the underlying collateral; and (iv) whether scheduled interest payments are past due. The recognition of credit impairment losses for available-for-sale debt securities are recorded as an allowance for credit losses with an offsetting charge to net income. Improvements to estimated credit losses for available-for-sale debt securities are recognized immediately in net income. If we believe a decline in the fair value of a particular fixed maturity available-for-sale investment is not credit impaired, we record the decline as an unrealized loss net of tax in Accumulated Other Comprehensive Income (Loss) in Stockholders’ Equity on our Consolidated Balance Sheets. The evaluation of securities for credit impairment is a quantitative and qualitative process, which is subject to risks and uncertainties and is intended to determine whether, and to what extent, declines in the fair value of investments should be recognized in current period earnings. The risks and uncertainties include changes in general economic conditions, the issuer’s or guarantor’s financial condition and/or future prospects, the impact of regulatory actions on the investment portfolio, the performance of the underlying collateral, the effects of changes in interest rates or credit spreads and the expected recovery period. With respect to Ambac insured securities owned, future cash flows used to measure credit impairment represents the sum of (i) the bond’s intrinsic cash flows and (ii) the estimated AAC claim payments. Ambac’s assessment about whether a decline in value is considered a credit impairment reflects management’s current judgment regarding facts and circumstances specific to a security and the factors noted above. If that judgment changes, Ambac may ultimately record a charge for credit impairment in future periods. Ambac has made certain accounting policy elections related to accrued interest receivable ("AIR") for available-for-sale investments under CECL. Elections include: i) not measuring AIR for credit impairment, instead AIR is written off when it becomes 90 days past due; ii) writing off AIR by reversing interest income; iii) presenting AIR separately in Other Assets on the balance sheet and iv) excluding AIR from amortized cost balances in required CECL disclosures found in Note 4. Investments . AIR at December 31, 2023 and 2022 was $14 and $10, respectively. Refer to Note 4. Investments for further credit impairment disclosures.
Net Premiums Earned	Premiums Legacy Financial Guarantee Insurance Gross premiums were received either upfront or in installments. For premiums received upfront, an unearned premium revenue (“UPR”) liability was established, which was initially recorded as the cash amount received. For installment premium transactions, a premium receivable asset and offsetting UPR liability was initially established in an amount equal to: (i) the present value of future contractual premiums due (the “contractual” method) or (ii) if the underlying insured obligation is a homogenous pool of assets which are contractually prepayable, the present value of premiums to be collected over the expected life of the transaction (the “expected” method). An appropriate risk-free rate corresponding to the weighted average life of each policy and currency is used to discount the future premiums contractually due or expected to be collected. For example, U.S. dollar exposures are discounted using U.S. Treasury rates while exposures denominated in a foreign currency are discounted using the appropriate risk-free rate for the respective currency. The weighted average risk-free rate at December 31, 2023 and 2022, was 3.2%. and 3.0%, respectively, and the weighted average period of future premiums used to estimate the premium receivable at December 31, 2023 and 2022, was 7.7 years and 8.0 years, respectively. Insured obligations consisting of homogeneous pools for which Ambac uses expected future premiums to estimate the premium receivable include residential mortgage-backed securities ("RMBS"). As prepayment assumptions change for homogenous pool transactions, or if there is an actual prepayment for a “contractual” method installment transaction, the related premium receivable and UPR are adjusted in equal and offsetting amounts with no immediate effect on earnings using new premium cash flows and the then current risk-free rate corresponding to the initial weighted average life of the related policy. For both upfront and installment premium policies, premium revenues are earned over the life of the financial guarantee contract in proportion to the insured principal amount outstanding at each reporting date (referred to as the level-yield method). For installment paying policies, the premium receivable discount, equating to the difference between the undiscounted future installment premiums and the present value of future installment premiums, is accreted as premiums earned in proportion to the premium receivable balance at each reporting date. When a bond issue insured by Ambac has been retired early, typically due to an issuer call, any remaining UPR is recognized at that time to the extent the financial guarantee contract is legally extinguished, causing accelerated premium revenue. For installment premium paying transactions, we offset the recognition of any remaining UPR by the reduction of the related premium receivable to zero (as it will not be collected as a result of the retirement), which may cause negative accelerated premium revenue. Certain obligations insured by Ambac have been legally defeased whereby government securities are purchased by the issuer with the proceeds of a new bond issuance, or less frequently with other funds of the issuer, and held in escrow. The principal and interest received from the escrowed securities are then used to retire the Ambac-insured obligations at a future date either to their maturity date (a refunding) or a specified call date (a pre-refunding). Ambac has evaluated the provisions in policies issued on these obligations and determined those insurance policies have not been legally extinguished. For policies with refunding securities, premium revenue recognition is not impacted as the escrowed maturity date is the same as the previous legal maturity date. For policies with pre-refunding securities, the maturity date of the pre-refunded security has been shortened from its previous legal maturity. Although premium revenue recognition has not been accelerated in the period of the pre-refunding, it results in an increase in the rate at which the policy's remaining UPR is to be recognized. For financial guarantee contracts, the issuer's ability and willingness to pay its insured debt obligation impacts the payment of policy losses by Ambac as well as the receipt of premiums from the issuer. As such, management leverages its existing loss reserve estimation process to evaluate credit impairment for premium receivables. Key factors in assessing credit impairment include historical premium collection data, internal risk classifications, credit ratings and loss severities. For structured finance transactions involving special purpose entities, we further evaluate the priority of premiums paid to Ambac within the contractual waterfall, as required by bond indentures. Ambac has a formal quarterly credit impairment review process for premium receivables. Management utilizes either a discounted cash flow ("DCF") or probability of default/loss given default ("PD/LGD") approach to estimate credit impairment on premium receivables. The DCF approach utilizes expected cash flows developed by Ambac's Risk Management Group using the same (or similar) models used for estimating loss reserves where such models can identify shortfalls in premiums. Credit impairment using the DCF approach is equal to the difference between amortized cost and the present value of expected cash flows. Credit impairment under the PD/LGD approach is the product of (i) the premium receivable carrying value, (ii) internally developed default probability (considering internal ratings and average life), and (iii) internally developed loss severities. Refer to Note 7. Insurance Contracts for further credit impairment disclosures. AAC has reinsurance in place pursuant to surplus share treaties and facultative reinsurance agreements. Similar to gross premiums, premiums ceded to reinsurers were paid either upfront or in installments. For premiums paid upfront, a deferred ceded premium asset was established which is initially recorded as the cash amount paid. For installment premiums, a ceded premiums payable liability and offsetting deferred ceded premium asset were initially established in an amount equal to: i) the present value of future contractual premiums due or ii) if the underlying insured obligation is a homogenous pool of assets, the present value of expected premiums to be paid over the life of the transaction. An appropriate risk-free rate corresponding to the weighted average life of each policy and exposure currency is used to discount the future premiums contractually due or expected to be collected. Premiums ceded to reinsurers reduce the amount of premiums earned by Ambac from its financial guarantee insurance policies. For both upfront and installment premiums, ceded premiums written are primarily recognized in earnings in proportion to and at the same time as the related gross premium revenue is recognized. For premiums paid to reinsurers on an installment basis, Ambac records the present value of future ceding commissions as an offset to ceded premiums payable, using the same assumptions noted above for installment premiums. Specialty Property and Casualty Insurance Gross written premiums on insurance policies are recorded at the inception of the policy and can be received on an upfront or installment basis. Ceded premiums written are based on contractual terms applied against related gross written premiums. Premiums, net of reinsurance, are recognized as revenue on a daily pro-rata basis over the term of the insured risk. Unearned premiums and Deferred ceded premiums represents the portion of gross and ceded premiums written that relate to unexpired risk, respectively.
Loans	Loans Loans are reported at either their outstanding principal balance less unamortized discount or at fair value. • Loans not held by consolidated VIEs are reported at their outstanding principal balance less unamortized discount and are reported within Other assets on the Consolidated Balance Sheet. Interest income is earned using the effective interest method based upon interest accrued on the unpaid principal balance adjusted for accretion of discounts. A loan is considered impaired when, based on the financial condition of the borrower, it is probable that Ambac will be unable to collect all principal and interest due according to the contractual terms of the loan agreement. Ambac has a formal quarterly credit impairment review process for these loans. The key factors in assessing credit impairment are internal credit ratings and loss severities. Management utilizes a PD/LGD approach, similar to the one described above for financial guarantee premium receivables, which is applied to the loan carrying value. • Loans held by VIEs consolidated as required under the Consolidation Topic of the ASC are carried at fair value under the fair value option election with changes in fair value recorded in Income (loss) on variable interest entities on the Consolidated Statements of Total Comprehensive Income (Loss). Such loans are reported as Loans, at fair value within the Variable interest entity assets section of the Consolidated Balance Sheet.
Derivative Contracts	Derivative Contracts The Company has entered into derivative contracts primarily to hedge certain economic risks inherent in its asset and liability portfolios. None of Ambac’s derivative contracts were designated as hedges under the Derivatives and Hedging Topic of the ASC. Ambac's derivatives have consisted primarily of interest rate swaps and futures contracts. • Ambac's current derivatives portfolio consists of certain legacy interest rate swaps executed in connection with financial guarantee client financings. In recent years, Ambac's interest rate derivatives portfolio consisted primarily of interest rate swaps and futures contracts to economically hedge interest rate risk in the financial guarantee and investment portfolios, managed on the basis of its net sensitivity to changes in interest rates. The economic hedge positions of the portfolio were fully exited in early 2023. Changes in the fair value of these interest rate derivatives are recorded, along with changes in fair value of other derivative contracts, within Net gains (losses) on derivative contracts on the Consolidated Statements of Total Comprehensive Income (Loss). • VIEs consolidated under the Consolidation Topic of the ASC entered into derivative contracts to meet specified purposes within their securitization structure. Changes in fair value of consolidated VIE derivatives are included within Income (loss) on variable interest entities on the Consolidated Statements of Total Comprehensive Income (Loss). All derivatives are recorded on the Consolidated Balance Sheets at fair value on a gross basis; assets and liabilities are netted by counterparty only when a legal right of offset exists, and are included in Other assets and Other liabilities, respectively. Variation payments on centrally cleared swaps and futures contracts are considered settlements of the associated derivative balances and are reflected as a reduction to derivative liabilities or assets on the Consolidated Balance Sheets. For other derivatives, Ambac has determined that the amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral may not be used to offset amounts due under the derivative instruments in the normal course of settlement. Therefore, such amounts are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement and are included in Other assets on the Consolidated Balance Sheets. Refer to Note 9. Derivative Instruments for further discussion of the Company’s use of derivative instruments and their impact of the consolidated financial statements. Refer to Note 5. Fair Value Measurements
Goodwill and Intangible Assets, Policy	Goodwill Goodwill is attributable to acquisitions in the Insurance Distribution segment and represents the acquisition cost in excess of the fair value of net assets acquired, including identifiable intangible assets. Goodwill is assigned at acquisition to the applicable reporting unit of the acquired entity giving rise to the goodwill. Goodwill is not amortized but is subject to impairment testing. Goodwill impairment tests are performed annually or more frequently if circumstances indicate a possible impairment. The annual test of goodwill impairment is as of October 1st of each year. Depending on the reporting unit, management utilizes one of two approaches for impairment testing. Under the first approach, qualitative factors are first assessed to determine if it is more likely than not that the fair value of the reporting unit is less than its carrying amount. If it is more likely than not, then a quantitative impairment evaluation is performed. Under the second approach, management bypasses the qualitative evaluation and proceeds directly to the quantitative evaluation. The quantitative evaluation under both of the above approaches compares the estimated fair value of the reporting unit with its carrying value (including goodwill and identifiable intangible assets). An impairment is recognized for the excess of the carrying amount of the reporting unit over it estimated fair value. If the reporting unit’s estimated fair value exceeds its carrying value, goodwill is not impaired. There have been no accumulated impairment losses since this goodwill was established. Intangible Assets Financial Guarantee Insurance intangible: Upon Ambac's emergence from bankruptcy in 2013, an insurance intangible asset was recorded which represented the difference between the fair value and aggregate carrying value of the financial guarantee insurance and reinsurance assets and liabilities. The carrying values of financial guarantee insurance and reinsurance contracts continue to be reported and measured in accordance with their existing accounting policies. Pursuant to the Financial Services-Insurance Topic of the ASC, the insurance intangible is to be measured on a basis consistent with the related financial guarantee insurance and reinsurance contracts. The initial insurance intangible asset was assigned to groups of insurance and reinsurance contracts with similar characteristics and has been amortized using a level-yield method based on par exposure of the related groups. Finite-lived intangibles Ambac acquired identifiable intangible assets attributable to the Insurance Distribution segment. The intangible assets primarily relate to distribution relationships, non-compete agreements and trade names, all of which have finite lives and are amortized over their estimated useful lives using the straight-line method. The Company tests finite-lived acquired intangible assets for impairment if certain events occur or circumstances change indicating that the carrying amount of the intangible asset may not be recoverable. The carrying amount of the intangible asset is not recoverable if it exceeds the projected undiscounted cash flows expected to result from the use and eventual disposal of the asset or asset group. If deemed unrecoverable, an impairment loss is recognized for the excess carrying amount over the fair value. There have been no accumulated impairment losses since these finite-lived intangible assets were established. Indefinite-lived intangibles Ambac acquired identifiable intangible assets attributable to its acquisitions of carriers in both 2021 and 2022, which were accounted for as asset acquisitions (Specialty Property and Casualty Insurance segment). The intangible assets relate to insurance licenses which have indefinite lives and therefore are not amortized. The useful lives are re-evaluated each period to determine whether facts and circumstances continue to support an indefinite life. The Company tests indefinite-lived acquired intangible assets for impairment annually or more frequently if circumstances indicate a possible impairment. Ambac tests indefinite-lived intangibles for impairment as of October 1st of each year. If, after assessing qualitative factors, management believes it is more likely than not that the intangible assets are impaired, a quantitative impairment evaluation is performed. Management also has the option to bypass the qualitative evaluation and proceed directly to the quantitative evaluation. The quantitative test compares the estimated fair value of the intangible asset with its carrying value. An impairment is recognized for the excess of the carrying amount of the intangible asset over it estimated fair value. If the asset’s estimated fair value exceeds its carrying value, the intangible asset is not impaired. There have been no accumulated impairment losses since these indefinite-lived intangible assets were established.
Restricted Cash	Restricted Cash Cash that we do not have the right to use for general purposes is recorded as restricted cash in our consolidated balance sheets. Restricted cash includes (i) consolidated variable interest entity cash restricted to support the obligations of the consolidated VIEs and (ii) fiduciary cash held by Ambac's insurance distribution subsidiaries as described below. Fiduciary Funds As an intermediary, we hold funds, generally in a fiduciary capacity, for the account of third parties, typically as the result of premiums received from retail brokers or insureds that are in transit to insurers and claims due that are in transit from insurers. Since fiduciary assets are not available for corporate use, they are shown in the consolidated balance sheets as restricted cash and we present an equal and corresponding fiduciary liability relating to these funds representing amounts or claims or premiums due on our consolidated balance sheets (included in Other liabilities). Fiduciary funds are generally required to be kept in bank accounts subject to guidelines which emphasize capital preservation and liquidity. The Company is entitled to retain investment income earned on certain of these fiduciary funds in accordance with industry custom and practice and, in some cases, as supported by agreements with insureds. Restricted cash for net uncollected premiums and claims and the related fiduciary liabilities were $12 and $14 at December 31, 2023 and 2022, respectively.
Loss Reserves	Loss and Loss Adjustment Expenses Legacy Financial Guarantee The loss and loss adjustment expense reserve (“loss reserve”) policy relates only to Ambac’s non-derivative financial guarantee insurance business for insurance policies issued to beneficiaries, including VIEs, for which we do not consolidate the VIE. Losses and loss expenses are based upon estimates of the ultimate aggregate losses inherent in the insured portfolio as of the reporting date. The policy for derivative contracts is discussed in the “Derivative Contracts” section above. A loss reserve is recorded on the balance sheet on a policy-by-policy basis based upon the present value ("PV") of expected net claim cash outflows or expected net recovery cash inflows, discounted at risk-free rates. The estimate for future net cash flows consider the likelihood of all possible outcomes that may occur from missed principal and/or interest payments on the insured obligation. This estimate also considers future recoveries related to remediation strategies and other contractual or subrogation-related cash flows. • Net claim cash outflow policies represent contracts where the PV of expected cash outflows are greater than the PV of expected recovery cash inflows. For such policies, a “loss and loss adjustment expense reserves” liability is recorded for the excess of the PV of expected net claim cash outflows over the unearned premium revenue. • Net recovery cash inflow policies represent contracts where the PV of expected recovery cash inflows are greater than the PV of expected claim cash outflows. For such policies, a “Subrogation recoverable” asset is recorded. The evaluation process for determining expected losses is subject to certain judgments based on our assumptions regarding the probability of default by the issuer of the insured security, probability of settlement outcomes (which may include commutation settlements, refinancing and/or other settlement outcomes) and expected severity of credits for each insurance contract. Ambac’s loss reserves are based on management’s ongoing review of the financial guarantee credit portfolio. Active surveillance of the insured portfolio enables Ambac’s Risk Management Group ("RMG") to track credit migration of insured obligations from period to period and update internal classifications and credit ratings for each transaction. Non-adversely classified credits are assigned a Class I rating while adversely classified credits are assigned a rating of Class IA through Class V. The criteria for an exposure to be assigned an adversely classified credit rating includes the deterioration of an issuer’s financial condition, underperformance of the underlying collateral (for collateral dependent transactions such as mortgage-backed or student loan securitizations), poor performance by the servicer of the underlying collateral and other adverse economic events or trends. The servicer of the underlying collateral of an insured securitization transaction is a consideration in assessing credit quality because the servicer’s performance can directly impact the performance of the related issue. All credits are assigned risk classifications by RMG using the following guidelines: CLASS I – “Fully Performing - Meets Ambac Criteria with Remote Probability of Claim” - Credits that demonstrate adequate security and structural protection with a strong capacity to pay interest, repay principal and perform as underwritten. Factors supporting debt service payment and performance are considered unlikely to change and any such change would not have a negative impact upon the fundamental credit quality. Through ongoing surveillance, Ambac may also designate Class I credits into one or more of the following categories: • Survey List - credits that may lack information or demonstrate a weakness but further deterioration is not expected. • Watch List - credits that demonstrate the potential for future material adverse development due to such factors as long-term uncertainty about a particular sector, a certain structural element, large exposure concentration or concern related to the issuer or transaction or the overall financial and economic sustainability. CLASS IA – “Potential Problem with Risks to be Dimensioned” - Credits that are fully current and monetary default or claims-payment are not anticipated. The issuer’s financial condition may be deteriorating or the credits may lack adequate collateral. A structured financing may also evidence weakness in its fundamental credit quality as evidenced by its under-performance relative to its modeled projections at underwriting, issues related to the servicer’s ability to perform or questions about the structural integrity of the transaction. While certain of these credits may still retain an investment grade rating, they usually have experienced or are vulnerable to a ratings downgrade. Further investigation is required to dimension and correct any deficiencies. A complete legal review of documents may be required. An action plan should be developed with triggers for future classification changes upward or downward. CLASS II – “Substandard Requiring Intervention” - Credits whose fundamental credit quality has deteriorated to the point that timely payment of debt service may be jeopardized by adversely developing trends of a financial, economic, structural, managerial or political nature. No claim payment is currently foreseen but the probability of loss or claim payment over the life of the transaction is now existent (generally 10% or greater probability). Class II credits may be border-line or below investment grade (BBB- to B). Prompt and sustained action must be taken to execute a comprehensive loss mitigation plan and correct deficiencies. CLASS III – “Doubtful with Clear Potential for Loss” - Credits whose fundamental credit quality has deteriorated to the point that timely payment of debt service has been or will be jeopardized by adverse trends of a financial, economic, structural, managerial or political nature which, in the absence of positive change or corrective action, are likely to result in a loss. The probability of monetary default or claims paying over the life of the transaction is generally 50% or greater. Full exercise of all available remedial actions is required to avert or minimize losses. Class III credits will generally be rated below investment grade (B to CCC). CLASS IV – “Imminent Default or Defaulted” - Monetary default or claim payments have occurred or are expected imminently. Class IV credits are generally rated D. CLASS V – “Fully Reserved” - The credit has defaulted and payments have occurred. The claim payments are scheduled and known, reserves have been established to fully cover such claims, and no claim volatility is expected. The population of credits evaluated in Ambac’s loss reserve process are: (i) all adversely classified credits and ii) non-adversely classified credits which had an internal Ambac rating downgrade since the transaction’s inception. One of two approaches is then utilized to estimate losses to ultimately determine if a loss reserve should be established. • The first approach is a statistical expected loss approach, which considers the likelihood of all possible outcomes. The “base case” statistical expected loss is the product of: (i) the par outstanding on the credit; (ii) internally developed default information (taking into consideration internal ratings and average life of an obligation); (iii) internally developed loss severities; and (iv) a discount factor. The loss severities and default information are based on rating agency information, are specific to each bond type and are established and approved by senior RMG officers. For certain credit exposures, Ambac’s additional monitoring, loss remediation efforts and probabilities of potential settlement outcomes may provide information relevant to adjust this estimate of “base case” statistical expected losses. RMG may accept the “base case” statistical expected loss as the best estimate of expected loss or assign multiple probability weighted scenarios to determine an adjusted statistical expected loss that better reflects management’s view of a given transaction’s expected losses, as well as the potential for additional remediation activities (e.g., commutations). • The second approach entails the use of cash-flow based models to estimate expected losses (future claims, net of potential recoveries, expected to be paid to the holder of the insured financial obligation). Ambac’s RMG group will consider the likelihood of all possible outcomes and develop appropriate cash flow scenarios. This approach can include the utilization of internal or third party models and tools to project future losses and resultant claim payment estimates. We utilize cash flow models for RMBS, student loans and other exposures. RMBS and student loan models use historical performance of the collateral pools in order to then derive future performance characteristics, such as default and voluntary prepayment rates, which in turn determine projected future claim payments. In other cases, such as many public finance exposures we do not specifically forecast resources available to pay debt service in the cash flow model itself. Rather, we consider the issuers’ overall ability and willingness to pay, including the fiscal, economic, legal and political framework to develop projected future claim payment estimates. In this approach, a probability-weighted expected loss estimate is developed based on assigning probabilities to multiple claim payment scenarios and applying an appropriate discount factor. Additionally, we consider the issuer’s ability to refinance an insured issue, Ambac’s ability to execute a potential settlement (i.e., commutation) of the insurance policy, including the impact on future installment premiums, and/or other restructuring possibilities in our scenarios. The commutation scenarios and the related probabilities of occurrence vary by transaction, depending on our view of the likelihood of negotiating such a transaction with issuers and/or investors. The discount factor applied to the statistical expected loss approach is based on a risk-free discount rate corresponding to the remaining expected weighted-average life of the exposure and the exposure currency. For the cash flow scenario approach, discount factors are applied based on a risk-free discount rate term structure and correspond to the date of each respective cash flow payment or recovery and the exposure currency. Discount factors are updated for the current risk-free rate each reporting period. Ambac establishes loss expense reserves based on our estimate of expected net cash outflows for loss expenses, such as legal and consulting costs. Below we provide further details of our loss reserve models for both RMBS and student loan exposures: RMBS Expected Loss Estimate Ambac insures RMBS transactions collateralized by (i) first-lien mortgages; and (ii) second-lien mortgage loans such as closed-end seconds and home equity lines of credit. If the borrower defaults on the payments due under these loans and the property is subsequently liquidated, the liquidation proceeds are first utilized to pay off the first-lien loan (as well as other costs) and any remaining funds are applied to pay off the second-lien loan. As a result of this subordinate position to the first-lien loan, second-lien loans may carry a significantly higher severity in the event of a loss. Ambac primarily utilizes a cash flow model (“RMBS cash flow model”) to develop estimates of projected losses for both our first and second lien transactions. The RMBS cash flow model projects collateral performance utilizing a combination of historical performance along with the most recent loan status information to project future collateral performance. In addition to the base case, we analyze historical volatility of performance to develop stress and upside cases. The highest probability is assigned to the base case, with lower probabilities to the stress and upside cases. For the liabilities of the transaction which we insure, we generally utilize waterfall projections generated from a tool provided by a market accepted vendor. This waterfall tool allows us to capture the impact of each transaction’s specific structure (e.g., the waterfall priority of payments, triggers, redemption priority) to generate our specific projected claims profile in the base, upside and downside scenarios. On a monthly basis, we compare monthly claims submitted against the trustees’ reports, waterfall projections and our understanding of the transactions’ structures to identify and resolve discrepancies. In our experience, market performance and model characteristics change and therefore need to be updated and reflected in our models through time. As such, we conduct regular reviews of current models, alternative models and the overall approach to loss estimation. Student Loan Expected Loss Estimate The student loan insured portfolio consists of credits collateralized by private student loans. The calculation of loss reserves for our student loan portfolio involves evaluating numerous factors that can impact ultimate losses. Since our policies cover timely interest and ultimate principal payment, our loss projections must make assumptions for many factors covering a long horizon. Key assumptions that will impact ultimate losses include, but are not limited to, the following: collateral performance (which is highly correlated to the economic environment); interest rates; operating risks associated with the issuer, servicers, special servicers, and administrators; investor appetite for tendering or commuting insured obligations; and as applicable, Ambac’s ability and willingness to commute policies. In addition, we consider in our student loan loss projections the potential impact, if any, of proposed or final regulatory actions or orders, including by the Consumer Financial Protection Bureau ("CFPB"), affecting our insured transactions. We develop and assign probabilities to multiple cash flow scenarios based on each transaction’s unique characteristics. Probabilities assigned are based on available data related to the credit, information from contact with the issuer (if applicable), and any economic or market information that may impact the outcomes of the various scenarios being evaluated. Our base case usually projects deal performance out to maturity using expected loss assumptions. As appropriate, we also develop other cases that incorporate various upside and downside scenarios that may include changes to defaults and recoveries. Specialty Property and Casualty Loss and loss adjustment expense reserves for Specialty Property and Casualty policies represent management's estimate of the ultimate liability for unpaid losses and loss expenses for claims that have been reported and claims that have been incurred but not yet reported ("IBNR") as of the balance sheet date. Loss and loss adjustment expense reserves do not represent an exact calculation of the liability, but instead represent management estimates, primarily utilizing actuarial expertise and projection methods that develop estimates for the ultimate cost of claims and claim adjustment expenses. The reserves are estimated based upon experience and using a variety of actuarial methods. These estimates are reviewed and are subject to the impact of future changes in factors such as claim severity and frequency, underwriting and claims practices, changes in social and economic conditions including the impact of inflation, legal and judicial developments, medical cost trends and upward trends in damage awards. Our actuarial methods may also rely on external data, such as industry loss ratios, loss development factors, or trend factors. Such data while more mature than Everspan's own data may not be perfectly representative of the particular business written by Everspan. The ultimate amount for loss and loss adjustment expenses may be in excess, or less than, the amounts recorded on our financial statements. Because the establishment of claims and claim adjustment expense reserves is an inherently uncertain process involving estimates and judgment, currently estimated claims and claim adjustment expense reserves may change. Adjustments will be reflected as part of the net increase or reduction in loss and loss adjustment expense reserves in the periods in which they become known. Cumulative amounts paid and case reserves held as of the balance sheet date are subtracted from the estimate of the ultimate cost of claims and claim adjustment expenses to derive incurred but not reported (IBNR) reserves. There were no changes in methodology in the past year. Detailed claim data is typically insufficient to produce a reliable indication of the initial estimate for ultimate claims and claim adjustment expenses for an accident year. As a result, the initial estimate for an accident year is generally based on an exposure-based method using the loss ratio projection method. The loss ratio projection method develops an initial estimate of ultimate claims and claim adjustment expenses for an accident year by multiplying earned premium for the accident year by a projected loss ratio. The projected loss ratio is determined by analyzing prior period experience, and adjusting for loss cost trends, rate level differences, mix of business changes and other known or observed factors influencing the accident year relative to prior accident years. For prior accident years, the following estimation and analysis methods are principally used by the Company’s actuaries to estimate the ultimate cost of claims and claim adjustment expenses. These estimation and analysis methods are typically referred to as conventional actuarial methods. • The paid loss development method assumes that the future change (positive or negative) in cumulative paid losses for a given cohort of claims will occur in a stable, predictable pattern from year-to-year, consistent with the pattern observed in past cohorts. • The case incurred development method is the same as the paid loss development method, but is based on cumulative case-incurred losses rather than paid losses. • The Bornhuetter-Ferguson method uses an initial estimate of ultimate losses for a given product line reserve component, typically expressed as a ratio to earned premium. The method assumes that the ratio of additional claim activity to earned premium for that component is relatively stable and predictable over time and that actual claim activity to date is not a credible predictor of further activity for that component. The method is used most often for more recent accident years where claim data is sparse and/or volatile, with a transition to other methods as the underlying claim data becomes more voluminous and therefore more credible. While these are the principal methods utilized, the Company’s actuaries have available to them the full range of actuarial methods developed by the casualty actuarial profession. Most actuarial methods assume that past patterns demonstrated in the data will repeat themselves in the future. The Company performs a continuing review of its loss and loss adjustment expense reserves, including its reserving techniques and the impact of reinsurance. Since the reserves are based on estimates, the ultimate liability may be more or less than such reserves.
Reinsurance Accounting Policy	Reinsurance Recoverable The Company uses ceded reinsurance to transfer certain insurance risk, along with premiums written and earned, to other insurance carriers that agree to share in such risks. The primary purpose of the reinsurance is to (i) protect the Company, at a cost, from losses in excess of amounts it is willing to accept, (ii) protect the Company's capital, and (iii) within the Specialty Property and Casualty Insurance operations, to manage the Company's net retention on individual risks and overall exposure to losses while providing the Company the ability to offer policies with sufficient limits to meet policyholder needs. • Within its Specialty Property and Casualty Insurance segment, the Company generally enters into quota share reinsurance agreements whereby the Company cedes to the capacity providers (reinsurers) a substantial amount (generally 70% or more) of its gross liability under all policies issued by and on behalf of the Company by the MGA/U. Ambac is exposed to the credit risk of the reinsurer, or the risk that one of its reinsurers becomes insolvent or otherwise unable or unwilling to pay policyholder claims. This credit risk is generally mitigated by either selecting well capitalized, highly rated authorized capacity providers or requiring that the capacity provider post collateral to secure the reinsured risks, which in some instances, exceeds the related reinsurance recoverable. Amounts recoverable from reinsurers are estimated in a manner consistent with the associated loss and loss adjustment expense reserves. The Company reports its reinsurance recoverables net of an allowance for amounts that are estimated to be uncollectible. The reinsurance of risk does not legally relieve Ambac of its original liability to its policyholders. In the event that any of Ambac’s reinsurers are unable to meet their obligations under reinsurance contracts, Ambac would, nonetheless, be liable to its policyholders for the full amount of its policy. To minimize its credit exposure to losses from reinsurer insolvencies, Ambac (i) is entitled to receive collateral from certain reinsurance counterparties pursuant to the terms of the relevant reinsurance contracts and (ii) has certain cancellation rights that can be exercised by Ambac in the event of rating agency downgrades of a reinsurer (among other events and circumstances). For those reinsurance counterparties that do not currently post collateral, Ambac’s reinsurers are well capitalized, highly rated, authorized capacity providers. Ambac has a formal quarterly credit impairment review process whereby Ambac has elected to use the practical expedient of considering the fair value of collateral posted by reinsurers when evaluating credit impairment. To determine the total unsecured recoverable to be evaluated for credit impairment, Ambac nets the reinsurance recoverable amount by ceded premiums payable and the fair value of collateral posted, if any. The key factors in assessing credit impairment for reinsurance recoverables are independent rating agency credit ratings and loss severities. Management utilizes a probability of default/loss given default ("PD/LGD") approach, which is applied to the net unsecured reinsurance recoverable amount. Refer to Note 7. Insurance Contracts
Debt, Policy	Long-term Debt Long-term debt issued by Ambac is carried at par value less unamortized discount. Accrued interest and discount accretion on long-term debt is reported as Interest expense on the Consolidated Statements of Total Comprehensive Income (Loss). To the extent Ambac repurchases or redeems its long-term debt, such repurchases or redemptions may be settled for an amount different than the carrying value of the obligation. Any difference between the payment and carrying value of the obligation is reported in Net realized gains (losses) on extinguishment of debt on the Consolidated Statements of Total Comprehensive Income (Loss). For surplus note repurchases, the pro-rata purchase price related to principal and accrued interest is reported as a financing and operating activity, respectively, on the Statement of Cash Flows. For long-term debt issued by consolidated VIEs in which Ambac's variable interest arises from financial guarantees written by Ambac's subsidiaries ("LFG VIEs"), we may elect to use the fair value option on an instrument by instrument basis. When the fair value option is elected, changes in the fair value of the LFG VIEs' long-term debt is reported within Income (loss) on variable interest entities in the Consolidated Statements of Total Comprehensive Income (Loss), except for the portion of the total change in fair value of financial liabilities caused by changes in the instrument-specific credit risk which is presented separately in Other comprehensive income (loss). In cases where the fair value option has not been elected, the LFG VIEs' long-term debt is carried at par less unamortized discount, with interest expense reported within Income (loss) on variable interest entities in the Consolidated Statements of Total Comprehensive Income (Loss).
Noncontrolling Interest Policy [Policy Text Block]		Noncontrolling Interests Nonredeemable noncontrolling interests At December 31, 2023 and 2022, AAC had 4,596 shares of issued and outstanding Auction Market Preferred Shares ("AMPS") with a liquidation preference of $115 (reported as nonredeemable noncontrolling interest of $51 on Ambac's balance sheet). In 2022, Ambac purchased 905 shares of AMPS for $8. The difference between this amount paid to AMPS holders and the carrying amount was reflected as an increase to Net income attributable to common shareholders for approximately $1. The auction occurs every 28 days and the dividend rate has continuously been reset at the maximum, equal to the Reference Rate plus 200 basis points. Beginning July 1, 2023, the Reference Rate for the AMPS is one-month CME Term SOFR plus 0.11448 percent. Prior to July 1, 2023, the Reference Rate was one-month LIBOR. Under the terms of the AMPS, dividends may not be paid on the common stock of AAC unless all accrued and unpaid dividends on the AMPS for the then current dividend period have been paid, provided, that dividends on the common stock may be made at all times for the purpose of, and only in such amounts as are necessary for, enabling AFG (i) to service its indebtedness for borrowed money as such payments become due or (ii) to pay its operating expenses. If dividends are paid on the common stock as provided in the prior sentence, dividends on the AMPS become cumulative until the date that all accumulated and unpaid dividends have been paid on the AMPS. AAC has not paid dividends on its AMPS since 2010. Redeemable noncontrolling interests The Xchange, All Trans, Capacity Marine and Riverton acquisitions resulted in 80%, 85%, 80% and 80%, respectively, ownership of the acquired entities by Ambac. Under the terms of all the acquisition agreements, Ambac has call options to purchase the remaining interest from the minority owners (i.e., noncontrolling interests) and the minority owners have put options to sell their remaining interests to Ambac. Because the exercise of the put options are outside the control of Ambac, in accordance with the Distinguishing Liabilities from Equity Topic of the ASC, Ambac reports redeemable noncontrolling interests in the mezzanine section of its consolidated balance sheet. The redeemable noncontrolling interest is remeasured each period as the greater of: i. the carrying value under ASC 810, which attributes a portion of consolidated net income (loss) to the redeemable noncontrolling interest, and ii. the redemption value of the put option under ASC 480 as if it were exercisable at the end of the reporting period. Any increase (decrease) in the carrying amount of the redeemable noncontrolling interest as a result of adjusting to the redemption value of the put option is recorded as an offset to retained earnings. The impact of such differences on earnings per share are presented in Note 15. Net Income Per Share. Following is a rollforward of redeemable noncontrolling interest. Years ended December 31, 2023 2022 Beginning balance $ 20 $ 18 Fair value of redeemable noncontrolling interest at acquisition date 2 5 Net income attributable to redeemable noncontrolling interest (ASC 810) 1 1 Distributions (2) (1) Adjustment to redemption value (ASC 480 ) (5) (3) Ending Balance $ 17 $ 20
Short-Duration Contracts Revenue Recognition, Policy	Revenue Recognition Revenues for the Insurance Distribution business operations and certain revenues of a consolidated VIE are recognized in accordance with the Revenue from Contracts with Customers Topic of the ASC. The following steps are applied to recognize revenue: (i) identify the contract(s) with the customer, (ii) identify the performance obligations in the contract(s), (iii) determine the transaction price, and (iv) allocate the transaction price to the performance obligations in the contract and recognize revenue when (or as) the entity satisfies a performance obligation. A performance obligation is satisfied either at a point in time or over time depending on the nature of the product or service provided, and the specific terms of the contract with customers. Insurance Distribution Insurance Distribution performance obligations consist of underwriting and placing policies with insurers and, for certain products, providing claims servicing. Revenue from employer stop loss policies ("ESL") is apportioned to policy placement and claims servicing based on the relative stand-alone selling price of the respective performance obligations with policy placement revenue recognized upfront while claims servicing revenue is recognized over the claim adjustment period. Revenue from other insurance policies are recognized up front as no further performance obligations exist after policy placement. Revenue consists of base and profit-sharing commissions. • Base commissions, associated with policy placement and claims servicing, are estimated by applying the contractual commission percentages to estimated gross premiums placed. • Profit-sharing commissions represent variable consideration associated with policy placement only and are estimated based on expected loss ratios and the estimated gross premium for base commissions. Base and profit-sharing commissions are estimated with a constraint applied such that a significant reversal of revenue in the future is not probable. Revenue is reported in Commissions income on the Consolidated Statement of Total Comprehensive Income. Contract assets represent the Company's right to future consideration for services it has already transferred to the customer, which is subject to certain contingencies. Once the right to consideration becomes unconditional, it is reported as a receivable. Contract assets are evaluated for credit loss under CECL. Management utilizes a PD/LGD approach, similar to the one described above for financial guarantee premium receivables and loans. Contract liabilities represent the Company's obligation to transfer services for which it has already received consideration from the customer. Contract assets and receivables are reported as other assets, and contract liabilities are reported as other liabilities, on the Consolidated Balance Sheet. The Company’s costs to obtain customer contracts relate to certain commissions paid to independent agents for procuring policies. As these costs relate to the Company’s policy placement performance obligation to its customers, they are expensed as incurred. These costs are reported in Commission expenses on the Consolidated Statement of Total Comprehensive Income. Consolidated VIE Refer to Note 11. Variable Interest Entities for further discussion on Ambac's involvement with VIEs and triggering events resulting in consolidation. Ambac consolidated a VIE on December 31, 2023 which has a contract with a governmental entity to provide construction and facilities management services in return for periodic concession payments. These services have been identified as the VIE's performance obligations. Revenue is apportioned to these performance obligations based on their respective stand-alone selling prices. Revenue is estimated based on regularly updated cash flow projections. This is a long-term contract that contains a significant financing component related to construction. As the construction services have already been completed, revenue recognized for this performance obligation will solely consist of interest income. Facilities management services are provided, and thus recognized, over time and will consist of services revenue. Costs to fulfill the customer contract primarily relate to fees paid to vendors to provide the facilities management services and will be expensed as incurred. All revenue and expense items will be reported within Income (loss) from variable interest entities. Contract assets are evaluated for credit losses under CECL. Management utilizes a PD/LGD approach, similar to the one described above for financial guarantee premium receivables and loans. Contract assets are reported within Derivative and other assets in the Variable interest entity asset section of the Consolidated Balance Sheet.
Postretirement and Postemployment Benefits	Postretirement and Postemployment Benefits Ambac provides postretirement and postemployment benefits, including health and life benefits covering employees who meet certain age and service requirements. Ambac accounts for these benefits under the accrual method of accounting. Amounts related to the postretirement health benefits liability are established and charged to expense based on actuarial determinations.
Long Term Incentive and Stock Compensation Plan	Incentive Compensation Incentive compensation is a key component of our compensation strategy. Incentive compensation has two components: short term incentive compensation (consisting of an annual cash bonus) and long term incentive plan awards (consisting of deferred cash and awards of restricted and performance stock units). Annual decisions with regard to incentive compensation are generally made in the first quarter of each year and are based on the prior year's performance for the Company, the employee and the employee's business unit. In 2020, the Ambac 2013 Incentive Compensation Plan (the “2013 Incentive Plan”) was superseded by the 2020 Incentive Compensation Plan ("2020 Incentive Plan"). Both plans allow for the granting of stock options, restricted stock, stock appreciation rights, restricted and performance units and other awards to employees, directors and consultants that are valued or determined by reference to Ambac's common stock. Under these plans, Ambac has issued both cash and equity awards to US employees and consultants. In connection with the adoption of the 2020 Incentive Plan, all shares reserved but unissued under the 2013 Incentive Plan were transferred to the the 2020 Incentive Plan in addition to any shares underlying outstanding awards under the 2013 Incentive Plan as of June 2, 2020 that subsequently terminate by expiration or forfeiture, cancellation, or otherwise are not issued. Under the 2013 and 2020 Incentive Compensation Plans. Ambac recognizes compensation costs for all equity classified awards granted at fair value, which is measured on the grant date, and records forfeitures for unvested shares only when they occur. For awards that only include service and performance conditions, the fair value is the market price of Ambac stock on the grant date. For awards that also contain a market condition, specifically a total shareholder return ("TSR") modifier, the fair value is estimated using a Monte Carlo simulation. The types of equity awards granted to employees are as follows: • Restricted stock units — only require future service and accordingly the respective fair value is recognized as compensation expense over the relevant service period. • Performance stock units — require both future service and achieving specified performance targets to vest. Performance stock unit grants also include a market condition TSR modifier that will cause the total payout at the end the performance period to increase or decrease depending on Ambac's stock performance relative to a peer group. Compensation costs for all performance stock units are only recognized when the achievement of the performance conditions are considered probable. Once deemed probable, such compensation costs are recognized as compensation expense over the relevant service period. Compensation costs are initially based on the probable outcome of the performance conditions and adjusted for subsequent changes in the estimated or actual outcome each reporting period as necessary. Changes in the estimated or actual outcome of a performance condition are recognized by reflecting a retrospective adjustment to compensation cost in the current period.
Lessee, Operating Lease, Disclosure [Table Text Block]	Operating Leases A contract contains a lease if it conveys the right to control the use of identified property, plant, or equipment for a period of time in exchange for consideration. Ambac's evaluation of whether certain contracts contain leases requires judgment regarding what party controls the asset and whether the asset is physically distinct. Ambac is the lessee in leases which are classified as operating leases. Ambac recognizes a single lease cost, calculated so that the cost is allocated generally on a straight-line basis over the lease term within operating expenses in the Consolidated Statements of Total Comprehensive Income (Loss). The lease term commences on the earlier of the date when we become legally obligated for the rent payments or the date on which we take possession of the property. For such operating leases, Ambac recognizes a right-of-use ("ROU") asset and a lease liability, initially measured at the present value of the lease payments. The discount rate used to initially measure the ROU assets and lease liabilities reflects the estimated secured borrowing rate of the applicable Ambac subsidiary, which considers the rate of existing or recent debt obligations of the entity. All cash payments are classified within operating activities in the statement of cash flows.
Depreciation and Amortization	Depreciation and Amortization Depreciation of furniture and fixtures, certain information technology development costs and electronic data processing equipment is charged over the estimated useful lives of the respective assets, ranging from three five
Foreign Currency	Foreign Currency Financial statement accounts expressed in foreign currencies are translated into U.S. dollars in accordance with the Foreign Currency Matters Topic of the ASC. The functional currencies of Ambac's subsidiaries are the local currencies of the country where the respective subsidiaries are based, which are also the primary operating environments in which the subsidiaries operate. Foreign currency translation: Functional currency assets and liabilities of Ambac’s foreign subsidiaries are translated into U.S. dollars using exchange rates in effect at the balance sheet dates and the related translation adjustments, net of deferred taxes, are included as a component of Accumulated Other Comprehensive Income (Loss) in Stockholders' Equity. Functional currency operating results of foreign subsidiaries are translated using average exchange rates. Foreign currency transactions: The impact of non-functional currency transactions and the remeasurement of non-functional currency assets and liabilities into the respective subsidiaries' functional currency (collectively "foreign currency transactions gains/(losses)") are $(3), $11 and $(7) for the years ended December 31, 2023, 2022 and 2021, respectively. Foreign currency transactions gains/(losses) are primarily the result of remeasuring Ambac UK's assets and liabilities denominated in currencies (primarily the U.S. dollar and the Euro) other than its functional currency (the British Pound Sterling).
Income Taxes	Income Taxes Ambac files a consolidated U.S. Federal income tax return with its subsidiaries. Ambac and its subsidiaries also file separate or combined income tax returns in various states, local and foreign jurisdictions. Current tax assets and liabilities are recognized for taxes refundable or payable for the current year. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on current and deferred tax assets and liabilities of a change in tax rates is recognized in the period that includes the enactment date.
Net Income Per Share	Net Income Per Share
Reclassifications	Reclassifications and Rounding Reclassifications may have been made to prior years' amounts to conform to the current year's presentation. Certain amounts and tables in the consolidated financial statements and associated notes may not add due to rounding.
Adoption of New Accounting Standards	Adopted Accounting Standards There have been no new accounting standards adopted during 2023. Future Application of Accounting Standards Segment Reporting: In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280) - Improvement to Reportable Segment Disclosures . The ASU requires disclosure of the following: • Significant segment expenses regularly provided to the chief operating decision maker (CODM) and included within the reported measure(s) of a segment’s profit or loss. • The amount and composition of "other segment items". This amount reconciles segment revenue, less significant expenses, to the reported measure(s) of a segment’s profit or loss. • The CODM's title and position. • How the CODM uses the reported measure(s) of a segment’s profit or loss to assess segment performance and decide how to allocate resources. • All segment profit or loss and assets disclosures currently required annually by Topic 280, as well as those introduced by the ASU, to also be disclosed in interim periods. The ASU also permits a public entity to report multiple measures of a segment’s profit or loss as long as: i) all the reported measures of a segment’s profit or loss are used by the CODM for purposes of assessing performance and allocating resources; and ii) the measure closest to GAAP is also provided. The ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. Ambac will adopt this ASU for the annual reporting period ending December 31, 2024 and we are evaluating its impact on Ambac's financial statements. Income Taxes: In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures . The enhancements in the ASU include the following: • Within the rate reconciliation table, disclosure of additional categories of information about federal, state and foreign income taxes and providing more details about the reconciling items in some categories if the items meet a quantitative threshold. • Annual disclosure of income taxes paid (net of refunds received) disaggregated by federal (national), state and foreign taxes and disaggregation of the information by jurisdiction based on a quantitative threshold. • Other disclosures include: i) income (or loss) from continuing operations before income tax expense (or benefit) disaggregated between domestic and foreign and ii) income tax expense (or benefit) from continuing operations disaggregated by federal (national), state, and foreign. The ASU is effective for annual periods beginning after December 15, 2024, with early adoption permitted. Ambac will adopt this ASU on January 1, 2025 and we are evaluating its impact on Ambac's financial statements.

Background and Business Descr_2

Background and Business Description Reorganization Costs (Tables)	12 Months Ended
	Dec. 31, 2023
Reorganizations [Abstract]
RMBS Litigation Settlement Impact on Consolidated Results	The total gain recognized in net income attributable to common stockholders related to entering into the BOA Settlement Agreement and the Nomura Settlement Agreement, including the redemption of the Sitka AAC Note following receipt of the BOA Settlement Payment, was as follows: Year Ended December 31, 2022 Losses and loss benefit (1) $ 362 Litigation recoveries 126 Net realized gains (losses) on extinguishment of debt (53) Net investment gains (losses), including impairments 5 Impact to net income attributable to common stockholders $ 440 (1) 2022 losses and loss benefit relating to R&W recoveries were $123.

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies Supplemental Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2023
Schedule of Cash Flow Supplemental Information [Line Items]
Schedule of Supplemental Cash Flow Information [Table Text Block]	Supplemental Disclosure of Cash Flow Information Year Ended December 31, 2023 2022 2021 Cash paid during the period for: Income taxes $ 11 $ 6 $ 15 Interest on long-term debt 50 283 80 Non-cash investing and financing activities: Exchange of investments in Puerto Rico bonds for new securities issued in the restructuring transactions — 185 — Decrease in long-term debt as a result of surplus notes exchanges — — 71 Securities acquired (transferred) in transactions related to Puerto Rico restructurings (1) 508 — Loans acquired through financial guarantee subrogation — 20 — VIE long-term debt issued related to Puerto Rico restructurings — 583 — Decrease in VIE loans as a result of de-consolidations 133 — — Decrease in VIE long-term debt as a result of de-consolidations 133 — — Increase in VIE long-term debt as a result of consolidations 89 — — December 31, 2023 2022 2021 Reconciliation of cash, cash equivalents, and restricted cash reported within the Consolidated Balance Sheets to the Consolidated Statements of Cash Flow: Cash and cash equivalents $ 16 $ 31 $ 17 Restricted cash 12 14 5 Variable Interest Entity Restricted cash 246 17 2 Total cash, cash equivalents, and restricted cash shown on the Consolidated Statements of Cash Flows 274 61 23
Cash Flow, Supplemental Disclosures [Text Block]	Supplemental information related to leases is as follows: Year Ended December 31, 2023 2022 Cash paid for amounts included in the measurement of operating lease liabilities $ 5 $ 5 Right-of-use assets obtained in exchange for operating lease liabilities (non-cash) 1 —
Redeemable Noncontrolling Interest	Following is a rollforward of redeemable noncontrolling interest. Years ended December 31, 2023 2022 Beginning balance $ 20 $ 18 Fair value of redeemable noncontrolling interest at acquisition date 2 5 Net income attributable to redeemable noncontrolling interest (ASC 810) 1 1 Distributions (2) (1) Adjustment to redemption value (ASC 480 ) (5) (3) Ending Balance $ 17 $ 20

Investments (Tables)

Investments (Tables)	12 Months Ended
Investments (Tables)	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments Held by Successor Ambac, by Contractual Maturity	The amortized cost and estimated fair value of available-for-sale investments, excluding VIE investments, at December 31, 2023, by contractual maturity, were as follows: Amortized Estimated Due in one year or less $ 544 $ 544 Due after one year through five years 581 560 Due after five years through ten years 293 271 Due after ten years 80 76 1,500 1,451 Residential mortgage-backed securities 239 250 Commercial mortgage-backed securities 19 19 Collateralized debt obligations 139 139 Other asset-backed securities 301 303 Total $ 2,197 $ 2,162
Summary of Gross Unrealized Losses and Fair Values of Ambac's Available-for-Sale Investments	The following table shows gross unrealized losses and fair values of Ambac’s available-for-sale investments, excluding VIE investments, which at December 31, 2023, did not have an allowance for credit losses under the CECL standard. This information is aggregated by investment category and length of time that the individual securities have been in a continuous unrealized loss position, at December 31, 2023 and 2022: December 31, 2023 December 31, 2022 Less Than 12 Months 12 Months or More Total Less Than 12 Months 12 Months or More Total Fair Gross Fair Value Gross Fair Value Gross Fair Gross Fair Value Gross Fair Value Gross Fixed maturity securities: Municipal obligations $ 7 $ — $ 16 $ 1 $ 23 $ 1 $ 21 $ 1 $ 7 $ 1 $ 28 $ 2 Corporate obligations 75 2 509 43 584 44 280 21 279 42 559 63 Foreign obligations 8 — 56 6 64 6 27 2 47 7 73 9 U.S. government obligations 27 1 37 2 63 4 40 3 19 1 58 4 Residential mortgage-backed securities 6 — 98 14 104 14 132 19 — — 132 19 Commercial mortgage-backed securities 3 — — — 3 — 3 — — — 3 — Collateralized debt obligations 1 — 93 1 95 1 90 3 36 1 126 4 Other asset-backed securities 57 1 35 1 92 1 198 4 5 1 203 5 184 4 844 68 1,028 71 791 53 392 53 1,183 106 Short-term 4 — — — 4 — 78 — 8 — 86 — Total temporarily impaired securities $ 187 $ 4 $ 844 $ 68 $ 1,032 $ 71 $ 869 $ 53 $ 400 $ 53 $ 1,269 $ 106
Investment	In addition to these investments, Ambac has unfunded commitments of $41 to private credit and private equity funds at December 31, 2023. Class of Funds 2023 2022 Redemption Frequency Redemption Notice Period Hedge funds (1) $ 112 $ 186 quarterly or semi-annually 90 days High yield and leveraged loans (2) (10) 85 80 daily 0 - 30 days Private credit (3) 84 84 quarterly if permitted 180 days if permitted Private equity (4) 70 47 quarterly if permitted 90 days if permitted Investment grade floating rate income (5) 52 63 weekly 0 days Equity market investments (6) (10) 38 64 daily or quarterly 0 - 90 days Real estate properties (7) 21 22 see footnote (7) see footnote (7) Insurance-linked investments (8) 1 1 see footnote (9) see footnote (9) Convertible bonds (9)(10) — 8 daily 0 days Total equity investments in pooled funds $ 463 $ 556 (1) This class seeks to generate superior risk-adjusted returns through selective asset sourcing, active trading and hedging strategies across a range of asset types. (2) This class of funds includes investments in high quality floating rate debt securities including ABS and corporate floating rate notes. (3) This class aims to obtain high long-term returns primarily through credit and preferred equity investments with low liquidity and defined term. (4) This class seeks to generate long-term capital appreciation through investments in private equity, equity-related and other instruments. (5) This class of funds includes investments in high quality floating rate debt securities including ABS and corporate floating rate notes. (6) This class of funds aim to achieve long-term growth through diversified exposure to global equity markets. (7) Investments consist of UK property to generate income and capital growth. (8) This class seeks to generate returns from insurance markets through investments in catastrophe bonds, life insurance and other insurance linked investments. This investment is restricted in connection with the unwind of certain insurance linked exposures. Ambac has redeemed its investment to the extent permitted by the fund. (9) This class seeks to generate total return from portfolios focused primarily on convertible securities. (10) These categories include fair value amounts totaling $77 and $61 at December 31, 2023 and 2022, respectively, that are readily determinable and are priced through pricing vendors, including for Equity market investments of $38 and $53, High yield and leveraged loans products $39 and $0, and Convertible bonds investments $0 and $8.
Summary of Net Investment Income	Net investment income (loss) was comprised of the following for the affected periods: Year Ended December 31, 2023 2022 2021 Fixed maturity securities $ 76 $ 61 $ 78 Short-term investments 22 11 — Loans — 1 — Investment expense (6) (6) (6) Securities available-for-sale and short-term 93 66 74 Fixed maturity securities - trading 7 (23) — Other investments 40 (26) 66 Total net investment income (loss) $ 140 $ 17 $ 139
Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments	The amortized cost and estimated fair value of available-for-sale investments, excluding VIE investments, at December 31, 2023 and 2022 were as follows: December 31, 2023 December 31, 2022 Amortized Allowance for Credit Losses Gross Gross Estimated Amortized Allowance for Credit Losses Gross Gross Estimated Fixed maturity securities: Municipal obligations $ 72 $ — $ 1 $ 1 $ 72 $ 44 — — 2 43 Corporate obligations 785 — 4 44 745 659 — 1 63 598 Foreign obligations 105 — 1 6 100 85 — — 9 76 U.S. government obligations 85 — 1 4 82 68 — — 4 65 Residential mortgage-backed securities 239 3 28 14 250 230 — 28 19 238 Commercial mortgage-backed securities 19 — — — 19 15 — — — 15 Collateralized debt obligations 139 — 1 1 139 141 — — 4 137 Other asset-backed securities (1) 301 — 3 1 303 227 — 2 5 224 1,744 3 40 71 1,710 1,469 — 31 106 1,395 Short-term 426 — — — 426 507 — — — 507 2,170 3 40 71 2,135 1,977 — 31 106 1,902 Fixed maturity securities pledged as collateral: Short-term 27 — — — 27 64 — — — 64 27 — — — 27 64 — — — 64 Total available-for-sale investments $ 2,197 $ 3 $ 40 $ 71 $ 2,162 2,041 $ — $ 31 $ 106 $ 1,966 (1)
Summary of Amounts Included in Net Realized (Losses) Gains and Other-Than-Temporary Impairments	The following table details amounts included in net investment gains (losses) and impairments included in earnings for the affected periods: Year Ended December 31, 2023 2022 2021 Gross realized gains on securities $ 1 $ 36 $ 14 Gross realized losses on securities (4) (18) (2) Foreign exchange (losses) gains (4) 14 (5) Credit impairments (3) — — Intent to sell impairments (12) — — Net investment gains (losses), including impairments $ (22) $ 31 $ 7
Unrealized Gain (Loss) on Investments	The portion of net unrealized gains (losses) related to securities classified as trading and equity securities, excluding those reported using the equity method, still held at the end of each period is as follows: Year Ended December 31, 2023 2022 2021 Net gains (losses) recognized during the period on trading and equity securities $ 25 $ (48) $ 23 Less: net gains (losses) recognized during the reporting period on trading and equity securities sold during the period 18 (26) 1 Unrealized gains (losses) recognized during the reporting period on trading and equity securities still held at the reporting date $ 7 $ (22) $ 22

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
Fair Value Measurements (Tables)	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Summary of Carrying Amount and Fair Value of Ambac's Financial Assets and Liabilities	The following table sets forth the carrying amount and fair value of Ambac’s financial assets and liabilities as of December 31, 2023 and 2022, including the level within the fair value hierarchy at which fair value measurements are categorized. As required by the Fair Value Measurement Topic of the ASC financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. December 31, 2023: December 31, 2022: Carrying Total Fair Fair Value Measurements Categorized as: Carrying Total Fair Fair Value Measurements Categorized as: Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Financial assets: Fixed maturity securities: Municipal obligations $ 99 $ 99 $ — $ 99 $ — $ 102 $ 102 $ — $ 102 $ — Corporate obligations 745 745 — 726 19 598 598 — 585 12 Foreign obligations 100 100 100 — — 76 76 76 — — U.S. government obligations 82 82 82 — — 65 65 65 — — Residential mortgage-backed securities 250 250 — 250 — 238 238 — 238 — Commercial mortgage-backed securities 19 19 — 19 — 15 15 — 15 — Collateralized debt obligations 139 139 — 139 — 137 137 — 137 — Other asset-backed securities 303 303 — 235 68 224 224 — 157 67 Fixed maturity securities, pledged as collateral: Short-term 27 27 27 — — 64 64 64 — — Short term investments 426 426 421 5 — 507 507 506 1 — Other investments (1) 475 463 77 — — 568 556 61 — — Cash, cash equivalents and restricted cash 28 28 27 2 — 44 44 43 1 — Other assets - Derivatives: Interest rate swaps—asset position 25 25 — — 25 27 27 — 1 26 Warrants 1 1 — — 1 1 1 — — 1 Other assets-loans 2 2 — — 2 10 10 — — 10 Variable interest entity assets: Fixed maturity securities: Corporate obligations, fair value option 2,072 2,072 — — 2,072 1,828 1,828 — — 1,828 Fixed maturity securities: Municipal obligation, trading — — — — — 43 43 — 43 — Fixed maturity securities: Municipal obligations, available-for-sale 95 95 — 95 — 96 96 — 96 — Restricted cash 246 246 246 — 17 17 17 — — Loans 1,663 1,663 — — 1,663 1,829 1,829 — — 1,829 Derivative assets: Interest rate swaps—asset position 190 190 — 190 — 190 190 — 190 — Derivative assets: Currency swaps—asset position 36 36 — 36 — 49 49 — 49 — Total financial assets $ 7,022 $ 7,010 $ 979 $ 1,795 $ 3,850 $ 6,726 $ 6,715 $ 833 $ 1,615 $ 3,772 Financial liabilities: Long term debt, including accrued interest $ 983 $ 697 $ — $ 679 $ 18 $ 1,065 $ 878 $ — $ 864 $ 14 Other liabilities - Derivatives: Interest rate swaps—liability position 35 35 — 35 — 38 38 — 38 — Liabilities for net financial guarantees written (2) 292 788 — — 788 159 476 — — 476 Variable interest entity liabilities: Long-term debt (includes $2,710 and $2,788 at fair value) 2,967 2,980 — 2,760 220 3,107 3,145 — 2,992 154 Derivative liabilities: Interest rate swaps—liability position 1,197 1,197 — 1,197 — 1,048 1,048 — 1,048 — Total financial liabilities $ 5,474 $ 5,697 $ — $ 4,671 $ 1,026 $ 5,418 $ 5,586 — 4,942 644 (1) Excluded from the fair value measurement categories in the table above are investment funds of $386 and $494 as of December 31, 2023 and 2022, respectively, which are measured using NAV as a practical expedient. Also excluded from the fair value measurements in the table above are equity securities with a carrying value of $13 and $12 as of December 31, 2023 and 2022, respectively, that do not have readily determinable fair values and have carrying amounts determined using the measurement alternative. (2) The carrying value of net financial guarantees written includes financial guarantee amounts in the following balance sheet items: Premium receivables; Reinsurance recoverable on paid and unpaid losses; Deferred ceded premium; Subrogation recoverable; Insurance intangible asset; Unearned premiums; Loss and loss adjustment expense reserves; Ceded premiums payable, premiums taxes payable and other deferred fees recorded in Other liabilities.
Summary of Changes in Level 3 Fair Value Category	The following tables present the changes in the Level 3 fair value category for the periods presented in 2023, 2022 and 2021. Ambac classifies financial instruments in Level 3 of the fair value hierarchy when there is reliance on at least one significant unobservable input to the valuation model. In addition to these unobservable inputs, the valuation models for Level 3 financial instruments typically also rely on a number of inputs that are readily observable either directly or indirectly. Thus, the gains and losses presented below include changes in the fair value related to both observable and unobservable inputs. Level-3 Financial Assets and Liabilities Accounted for at Fair Value VIE Assets and Liabilities Year ended December 31, 2023 Investments Derivatives Investments Loans Total Balance, beginning of period $ 79 $ 26 $ 1,828 $ 1,829 $ 3,762 Total gains/(losses) realized and unrealized: Included in earnings 1 — 200 142 343 Included in other comprehensive income 3 — 68 100 170 Purchases 6 — — — 6 Issuances — — — — — Sales — — — — — Settlements (2) — (24) (274) (300) Balance, end of period $ 87 $ 26 $ 2,072 $ 1,663 $ 3,848 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 1 $ — $ 200 $ 142 $ 343 The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 3 $ — $ 68 $ 100 $ 170 Level-3 Financial Assets and Liabilities Accounted for at Fair Value VIE Assets and Liabilities Year Ended December 31, 2022 Investments Derivatives Investments Loans Total Balance, beginning of period $ 91 $ 70 $ 3,320 $ 2,718 $ 6,199 Total gains/(losses) realized and unrealized: Included in earnings 1 (38) (789) (333) (1,160) Included in other comprehensive income (12) — (353) (279) (644) Purchases — — — — — Issuances — — — — — Sales — — — — — Settlements (1) (6) (349) (278) (633) Balance, end of period $ 79 $ 26 $ 1,828 $ 1,829 $ 3,762 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 1 $ (38) $ (789) $ (333) $ (1,160) The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ (12) $ — $ (353) $ (279) $ (644) Level-3 Financial Assets and Liabilities Accounted for at Fair Value Other Assets VIE Assets and Liabilities Year Ended December 31, 2021 Investments Derivatives Investments Loans Total Balance, beginning of period $ 78 $ 1 $ 84 $ 3,215 $ 2,998 $ 6,376 Total gains/(losses) realized and unrealized: Included in earnings 1 — (6) 176 59 230 Included in other comprehensive income 1 — — (32) (26) (58) Purchases 13 — — — — 13 Issuances — — — — — — Sales — — — — — — Settlements (2) (1) (8) (38) (313) (362) Balance, end of period $ 91 $ — $ 70 $ 3,320 $ 2,718 $ 6,199 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ (1) $ — $ (6) $ 176 $ 59 $ 227 The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ (1) $ — $ — $ (32) $ (26) $ (59)
Summary of Gains and Losses (Realized and Unrealized) Relating to Level 3 Assets and Liabilities Included in Earnings	Gains and losses (realized and unrealized) relating to Level 3 assets and liabilities included in earnings for the affected periods are reported as follows: Net Net Gains Income (Loss) Other Year Ended December 31, 2023 Total gains (losses) included in earnings for the period $ 1 $ — $ 341 $ — Changes in unrealized gains (losses) relating to financial instruments still held at the reporting date — — 341 — Year Ended December 31, 2022 Total gains (losses) included in earnings for the period $ 1 $ (38) $ (1,123) $ — Changes in unrealized gains (losses) relating to financial instruments still held at the reporting date 1 (39) (1,123) — Year Ended December 31, 2021 Total gains (losses) included in earnings for the period $ 1 $ (6) $ 235 $ — Changes in unrealized gains (losses) relating to financial instruments still held at the reporting date 1 (6) 235 —

Financial Guarantees in Force_2

Financial Guarantees in Force (Tables)	12 Months Ended
Financial Guarantees in Force (Tables)	Dec. 31, 2023
Guarantees [Abstract]
Schedule of Financial Guarantee Insurance In Force By Bond Type	As of December 31, 2023 and 2022, the legacy financial guarantee portfolio consisted of the types of guaranteed bonds as shown in the following table: Net Par Outstanding December 31, (1) 2023 2022 Public Finance: Housing revenue (2) $ 3,443 $ 5,491 Lease and tax-backed revenue 1,542 1,979 General obligation 1,051 1,301 Other 1,526 1,776 Total Public Finance 7,562 10,547 Structured Finance: Mortgage-backed and home equity 1,712 1,930 Investor-owned utilities 1,077 1,103 Other 526 579 Total Structured Finance 3,315 3,612 International Finance: Sovereign/sub-sovereign 4,221 4,077 Investor-owned and public utilities 2,855 2,583 Asset-backed and other 862 1,083 Transportation 726 711 Total International Finance 8,664 8,454 Total $ 19,541 $ 22,613 (1) Net Par Outstanding includes capital appreciation bonds, which are reported at the par amount at the time of issuance of the insurance policy as opposed to the current accreted value of the bond. (2) Includes $3,371 and $5,400 of Military Housing net par at December 31, 2023 and 2022, respectively.
Schedule of International Financial Guarantee Insurance In Force Portfolio By Location Of Risk	As of December 31, 2023 and 2022, the financial guaranteed portfolio by location of risk was as outlined in the table below: Net Par Outstanding December 31, 2023 2022 United States $ 10,877 $ 14,159 United Kingdom 7,502 7,223 Italy 576 644 Austria 307 310 Australia 266 259 France 12 14 Other international 1 4 Total $ 19,541 $ 22,613

Financial Guarantee Insurance_2

Financial Guarantee Insurance Contracts (Tables)	12 Months Ended
Financial Guarantee Insurance Contracts (Tables)	Dec. 31, 2023
Insurance [Line Items]
Effect of Reinsurance on Premiums Written and Earned	The effect of reinsurance on premiums written and earned was as follows: Year Ended Direct Assumed Ceded Net 2023: Written $ 249 $ 40 $ 244 $ 44 Earned 224 18 164 78 2022: Written $ 127 $ — $ 104 $ 23 Earned 126 — 69 56 2021: Written $ 2 $ — $ 35 $ (33) Earned 62 — 15 47
Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area [Table Text Block]	The following table summarizes net premiums earned by location of risk: Year Ended December 31, 2023 2022 2021 United States 65 $ 41 $ 27 United Kingdom 11 13 14 Other international 2 3 6 Total 78 $ 56 $ 47 Premium Receivables, including Credit Impairments Premium receivables at December 31, 2023 and 2022 were $290 and $269, respectively. Below is the gross premium receivable roll-forward, net of the allowance for credit losses, for the affected periods: Year Ended December 31, 2023 2022 2021 Beginning premium receivable $ 269 $ 323 $ 370 Premiums written on new business, net of commissions 210 117 10 Premium receipts (208) (139) (43) Adjustments for changes in expected and contractual cash flows for contracts (1) 6 (31) (27) Accretion of premium receivable discount for contracts 8 8 8 Consolidation of VIEs (1) — — Changes to allowance for credit losses 1 4 8 Other adjustments (including foreign exchange) (2) 4 (12) (4) Ending premium receivable (3) $ 290 $ 269 $ 323 (1) Adjustments for changes in expected and contractual cash flows are primarily due to indexation offset by reductions in insured exposure as a result of early policy terminations and unscheduled principal paydowns for financial guarantee policies. (2) Includes foreign exchange gains/(losses) of $4, ($13) and $(2) for 2023, 2022,and 2021 respectively. (3) Premium receivable includes premiums to be received in foreign denominated currencies most notably in British Pounds and Euros. At December 31, 2023, 2022 and 2021 premium receivables include British Pounds of $72 (£57), $71 (£59) and $108 (£80), respectively, and Euros of $13 (€12), $14 (€13) and $16 (€14), respectively. Management evaluates premium receivables for expected credit losses ("credit impairment") in accordance with the CECL standard, which is further described in Note 2. Basis of Presentation and Significant Accounting Policies . The key indicator management uses to assess the credit quality of legacy financial guarantee premium receivables is Ambac's internal risk classifications for the insured obligation determined by the Risk Management Group. Below is the amortized cost basis of financial guarantee premium receivables by risk classification code and asset class as of December 31, 2023 and 2022: Surveillance Categories as of December 31, 2023 Surveillance Categories as of December 31, 2022 Type of Guaranteed Bond I IA II III IV Total I IA II III IV Total Public Finance: Housing revenue $ 131 $ 3 $ 5 $ — $ — $ 139 $ 140 $ 3 $ 5 $ — $ — $ 148 Other 1 — — — — 1 2 — — — — 2 Total Public Finance 133 3 5 — — 140 142 3 5 — — 150 Structured Finance: Mortgage-backed and home equity — — — — 11 12 — — — — 11 11 Student loan — — — 7 — 7 1 1 — 7 — 8 Other 4 — — — — 4 4 — — — — 4 Total Structured Finance 4 — — 7 11 22 5 1 — 7 11 24 International: Sovereign/sub-sovereign 51 13 — — — 64 49 7 — 9 — 64 Investor-owned and public utilities 18 — — — — 18 18 — — — — 18 Other 3 — — — — 3 2 — — — — 2 Total International 72 13 — — — 85 70 7 — 9 — 85 Total (1) (2) $ 210 $ 16 $ 5 $ 7 $ 11 $ 248 $ 217 $ 10 $ 5 $ 16 $ 11 $ 259 (1) Excludes specialty property and casualty premium receivables of $46 and $16 at December 31, 2023 and 2022, respectively and has recorded an allowance for credit losses of less than a million in both periods. (2) The underwriting origination dates for all policies included are greater than five years prior to the current reporting date.
Summarized Future Gross Undiscounted Premiums Expected to be Collected and Future Expected Premiums Earned, Net of Reinsurance	The following table summarizes the future Legacy Financial Guarantee gross undiscounted premiums to be collected and future premiums earned, net of reinsurance at December 31, 2023: Future Premiums Collected (1) Future to be Earned Net of (2) Three months ended: March 31, 2024 $ 8 $ 5 June 30, 2024 6 4 September 30, 2024 7 4 December 31, 2024 5 4 Twelve months ended: December 31, 2025 26 16 December 31, 2026 25 16 December 31, 2027 24 15 December 31, 2028 23 14 Five years ended: December 31, 2033 93 55 December 31, 2038 54 28 December 31, 2043 25 9 December 31, 2048 12 4 December 31, 2053 2 1 Total $ 310 $ 173 (1) Future premiums to be collected are undiscounted, gross of allowance for credit losses, and are used to derive the discounted premium receivable asset recorded on Ambac's balance sheet. (2) Future premiums to be earned, net of reinsurance relate to the unearned premiums liability and deferred ceded premium asset recorded on Ambac’s balance sheet. The use of contractual lives for many bond types which do not have homogeneous pools of underlying collateral is required in the calculation of the premium receivable as further described in Note 2. Basis of Presentation and Significant Accounting Policies . This results in a different premium receivable balance than if expected lives were considered. If installment paying policies are retired or prepay early, premiums reflected in the premium receivable asset and amounts reported in the above table for such policies may not be collected. Future premiums to be earned also considers the use of contractual lives for many bond types which do not have homogeneous pools of underlying collateral, which may result in different unearned premium than if expected lives were considered. If those bonds types are retired early, premium earnings may be negative in the period of call or refinancing.
Schedule of Loss And Loss Expense Reserves And Subrogation Recoverable Table	Below are the components of the loss and loss adjustment expense reserves and the subrogation recoverable asset at December 31, 2023 and 2022: December 31, 2023: December 31, 2022: LFG LFG SPC Present Value of Expected SPC Present Value of Expected Balance Sheet Line Item Gross Loss and Claims and Recoveries Unearned Gross Loss and Gross Loss and Claims and Recoveries Unearned Gross Loss and Loss and loss adjustment expense reserves $ 197 $ 779 $ (55) $ (28) $ 893 $ 90 $ 787 $ (44) $ (28) $ 805 Subrogation recoverable — 1 (139) — (137) — 5 (276) — (271) Totals $ 197 $ 780 $ (194) $ (28) $ 756 $ 90 $ 791 $ (319) $ (28) $ 534 SPC = Specialty Property and Casualty, LFG = Legacy Financial Guarantee
Summary of Loss Reserve Roll-Forward, Net of Subrogation Recoverable and Reinsurance	Below is the loss and loss reserve expense roll-forward, net of subrogation recoverable and reinsurance, for the affected periods. Year Ended December 31, 2023 2022 2021 Beginning gross loss and loss adjustment expense reserves $ 534 $ (522) $ (397) Reinsurance recoverable 115 56 33 Beginning balance of net loss and loss adjustment expense reserves 419 (578) (430) Losses and loss expenses (benefit) incurred: Current year 37 4 — Prior years (69) (401) (89) Total (1)(2) (32) (397) (88) Loss and loss adjustment expenses (recovered) paid: Current year 4 7 — Prior years (194) (1,867) 59 Total (190) (1,860) 59 Foreign exchange effect — (2) — Ending net loss and loss adjustment expense reserves 577 883 (578) Impact of VIE consolidation (3) (7) (464) — Reinsurance recoverable (4) 186 115 56 Ending gross loss and loss adjustment expense reserves 756 534 (522) (1) Total losses and loss expenses (benefit) includes $(110), $(41) and $5 for the years ended December 31, 2023, 2022 and 2021, respectively, related to ceded reinsurance. (2) Ambac records the impact of estimated recoveries related to securitized loans in RMBS transactions that breached certain representations and warranties ("R&W's") by transaction sponsors within losses and loss expenses (benefit) for the Legacy Financial Guarantee Insurance segment. The losses and loss expense (benefit) incurred associated with changes in estimated R&W's for the year ended December 31, 2023, 2022 and 2021 was $0, $(123) and $20, respectively. Refer to Note 1. Background and Business Description to the Consolidated Financial Statements in this Annual Report on Form 10-K for details of the RMBS litigation settlements reached in October and December 2022. (3) Ambac consolidated one, three and zero LFG VIEs during the years ended December 31, 2023, 2022 and 2021, respectively as further discussed in Note 11. Variable Interest Entities . (4) Represents reinsurance recoverable on future loss and loss adjustment expenses. Additionally, the Balance Sheet line "Reinsurance recoverable on paid and unpaid losses" includes reinsurance recoverables (payables) of $8, $0 and $0 as of December 31, 2023, 2022 and 2021, respectively, related to previously presented loss and loss adjustment expenses and subrogation.
Summary of Information Related to Policies Currently Included in Ambac's Loss Reserves or Subrogation Recoverable	The tables below summarize information related to policies currently included in Ambac’s loss and loss adjustment expense reserves or subrogation recoverable at December 31, 2023 and 2022, excluding consolidated VIEs. Gross par exposures include capital appreciation bonds which are reported at the par amount at the time of issuance of the insurance policy as opposed to the current accreted value of the bond. The weighted average risk-free rate used to discount loss reserves at December 31, 2023 and 2022 was 3.9% and 3.9%, respectively. Surveillance Categories as of December 31, 2023 Surveillance Categories as of December 31, 2022 I IA II III IV V Total I IA II III IV V Total Number of policies 18 8 9 13 88 5 141 37 6 9 12 93 5 162 Remaining weighted-average contract period (in years) (1) 9 9 13 13 12 7 12 7 19 14 14 12 7 14 Gross insured contractual payments outstanding: Principal $ 429 $ 1,084 $ 430 $ 394 $ 1,473 $ 27 $ 3,838 $ 709 $ 200 $ 459 $ 1,000 $ 1,646 $ 34 $ 4,047 Interest 75 328 262 139 600 17 1,421 526 198 286 156 565 19 1,750 Total $ 505 $ 1,412 $ 692 $ 534 $ 2,073 $ 44 $ 5,259 $ 1,235 $ 399 $ 745 $ 1,156 $ 2,210 $ 53 $ 5,797 Gross undiscounted claim liability $ 1 $ 19 $ 41 $ 324 $ 772 $ 44 $ 1,202 $ 4 $ 4 $ 43 $ 446 $ 729 $ 53 $ 1,279 Discount, gross claim liability — (2) (7) (86) (323) (8) (426) (1) (1) (7) (162) (316) (9) (496) Gross claim liability before all subrogation and before reinsurance $ 1 $ 17 $ 34 $ 239 $ 450 $ 36 $ 777 $ 3 $ 3 $ 36 $ 284 $ 413 $ 43 $ 783 Less: Gross RMBS subrogation (2) $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — $ — $ (140) $ — $ (140) Discount, RMBS subrogation — — — — — — — — — — — — — — Discounted RMBS subrogation, before reinsurance — — — — — — — — — — — (140) — (140) Less: Gross other subrogation (3) (13) (2) — (27) (208) (11) (263) (14) (4) — (31) (172) (12) (233) Discount, other subrogation 2 — — 4 60 3 69 2 — — 5 42 4 54 Discounted other subrogation, before reinsurance (11) (2) — (23) (149) (8) (194) (12) (3) — (26) (130) (8) (179) Gross claim liability, net of all subrogation and discounts, before reinsurance $ (10) $ 15 $ 34 $ 215 $ 301 $ 28 $ 583 $ (9) $ — $ 36 $ 258 $ 143 $ 35 $ 464 Less: Unearned premium revenue $ — $ (12) $ (4) $ — $ (10) $ (1) $ (28) $ (2) $ (2) $ (5) $ (8) $ (10) $ (1) $ (28) Plus: Loss expense reserves — 3 — — 1 — 4 1 1 — 2 4 — 8 Gross loss and loss adjustment expense reserves $ (10) $ 6 $ 30 $ 215 $ 292 $ 27 $ 559 $ (10) $ (2) $ 32 $ 252 $ 137 $ 34 $ 444 Reinsurance recoverable reported on Balance Sheet (4) $ 1 $ — $ 8 $ 18 $ 3 $ — $ 30 $ 1 $ — $ 8 $ 21 $ 3 $ — $ 33 (1) Remaining weighted-average contract period is weighted based on projected gross claims over the lives of the respective policies. (2) RMBS subrogation represents Ambac’s estimate of subrogation recoveries from RMBS transaction sponsors for R&W breaches. (3) Other subrogation represents subrogation related to excess spread and other contractual cash flows on public finance and structured finance transactions, including RMBS. (4) Reinsurance recoverable reported on the Balance Sheet includes reinsurance recoverables of $30 and $33 related to future loss and loss adjustment expenses and $8 and $0 related to presented loss and loss adjustment expenses and subrogation at December 31, 2023 and 2022, respectively.
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	ntangible asset and accumulated amortization are included in the Consolidated Balance Sheets, as shown below. December 31, 2023 2022 Finite-lived Intangible Assets: Insurance intangible: Gross carrying value $ 1,258 $ 1,247 Accumulated amortization 1,013 981 Net insurance intangible asset 245 266 Other intangibles: Gross Carrying value 57 52 Accumulated amortization 10 6 Net other intangible assets 47 47 Total finite-lived intangible assets $ 292 $ 312 Indefinite-lived Intangible Assets: Insurance licenses $ 14 $ 14 Total intangible assets $ 307 $ 326
Premium Receivable, Allowance for Credit Loss	Below is a rollforward of the premium receivable allowance for credit losses as of December 31, 2023 and 2022: Year Ended December 31, 2023 2022 2021 Beginning balance $ 5 $ 9 $ 17 Current period provision (benefit) (1) (4) (6) Write-offs of the allowance — — (2) Recoveries of previously written-off amounts — — — Ending balance $ 4 $ 5 $ 9
Schedule of Financial Guarantee Insurance In Force By Bond Type	As of December 31, 2023 and 2022, the legacy financial guarantee portfolio consisted of the types of guaranteed bonds as shown in the following table: Net Par Outstanding December 31, (1) 2023 2022 Public Finance: Housing revenue (2) $ 3,443 $ 5,491 Lease and tax-backed revenue 1,542 1,979 General obligation 1,051 1,301 Other 1,526 1,776 Total Public Finance 7,562 10,547 Structured Finance: Mortgage-backed and home equity 1,712 1,930 Investor-owned utilities 1,077 1,103 Other 526 579 Total Structured Finance 3,315 3,612 International Finance: Sovereign/sub-sovereign 4,221 4,077 Investor-owned and public utilities 2,855 2,583 Asset-backed and other 862 1,083 Transportation 726 711 Total International Finance 8,664 8,454 Total $ 19,541 $ 22,613 (1) Net Par Outstanding includes capital appreciation bonds, which are reported at the par amount at the time of issuance of the insurance policy as opposed to the current accreted value of the bond. (2) Includes $3,371 and $5,400 of Military Housing net par at December 31, 2023 and 2022, respectively.
Reinsurance Recoverable, Credit Quality Indicator	The following table sets forth our three most significant reinsurers by amount of reinsurance recoverable as of December 31, 2023. Reinsurers Type of Insurance Rating (1) Reinsurance Recoverable (2) Unsecured Recoverable (3) General Reinsurance Company Specialty P&C A++ $ 81 $ 69 QBE Insurance Corporation Specialty P&C A 38 38 Assured Guaranty Re Ltd. Financial AA 25 — All other reinsurers 50 21 Total recoverables $ 195 $ 128 (1) Represents financial strength ratings from S&P for financial guarantee reinsurers and AM Best for specialty P&C reinsurers. (2) Represents reinsurance recoverables on paid and unpaid losses. Unsecured amounts from QBE Insurance Corporation is also supported by an unlimited, uncapped indemnity from Enstar Holdings (US). (3) Reinsurance recoverables reduced by ceded premiums payables due to reinsurers, letters of credit, and collateral posted for the benefit of Ambac.
Short-Duration Insurance Contracts, Schedule of Historical Claims Duration	The claim development tables that follow present, by accident year, incurred and cumulative paid claims and allocated claim adjustment expense on a historical basis. This claim development information is presented on an undiscounted, net of reinsurance basis since 2021, Everspan's entry into the Specialty P&C business. The claim development tables also provide the historical average annual percentage payout of incurred claims by age, net of reinsurance, as supplementary information (identified as unaudited in the tables below). The historical average annual percentage payout for incurred claims is subject to variability due to the impact of both large claim activity and subrogation recoveries, among other items. Commercial Auto Incurred Claims and Allocated LAE, Net of Reinsurance Accident Year Year ended December 31, IBNR Reserves at December 31, 2023 Cumulative Number of Reported Claims 2021 2022 2023 Unaudited 2021 $ — $ — $ 1 $ — 75 2022 8 8 3 1,112 2023 19 10 2,531 Total $ 28 Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Accident Year Year ended December 31, Liability for Loss and Loss Adjustment Expenses, Net of Reinsurance 2021 2022 2023 Unaudited 2021 $ — $ — $ — 2022 1 2 2021 - Before 2023 4 2023 2021 Total 6 22 — Total net liability 22 Average Annual Percentage Payout of Incurred Claims by Age, Unaudited Years 1 2 3 9.3 % 2.9 % 10.7 % Other Incurred Claims and Allocated LAE, Net of Reinsurance Accident Year Year Ended December 31, IBNR Reserves at December 31, 2023 Cumulative Number of Reported Claims 2021 2022 2023 Unaudited 2021 $ — $ — $ — $ — 0 2022 — — — 646 2023 16 8 11,595 Total $ 16 Cumulative Paid Claims and Allocated LAE, Accident Year Year Ended December 31, Liability for Loss and Loss Adjustment Expenses, Net of Reinsurance 2021 2022 2023 Unaudited 2021 $ — $ — $ — 2022 — — 2021 - Before 2023 2 2023 2021 Total 2 14 — Total net liability 14 Average Annual Percentage Payout of Incurred Claims by Age, Unaudited Years 1 2 3 3.1 % 0.9 % — %

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
Derivative Instruments (Tables)	Dec. 31, 2023
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]	The following tables summarize the location and gross fair values of individual derivative instruments and the impact of legal rights of offset as reported in the Consolidated Balance Sheets, as of December 31, 2023 and 2022. December 31, 2023: December 31, 2022: Gross Gross Net Amounts Gross Amount Net Amount Gross Gross Net Amounts Gross Amount Net Amount Other assets: Interest rate swaps $ 25 $ — $ 25 $ — $ 25 $ 27 $ — $ 27 $ — $ 27 Warrants 1 — 1 — 1 1 — 1 — 1 Total non-VIE derivative assets $ 26 $ — $ 26 $ — $ 26 $ 28 $ — $ 27 $ — $ 27 Other liabilities: Interest rate swaps $ 35 $ — $ 35 $ 35 $ — $ 38 $ — $ 38 $ 38 $ — Total non-VIE derivative liabilities $ 35 $ — $ 35 $ 35 $ — $ 38 $ — $ 38 $ 38 $ — Variable interest entities assets: Derivative and other assets: Interest rate swaps $ 190 $ — $ 190 $ 190 $ — $ 190 $ — $ 190 $ — $ 190 Currency swaps 36 — 36 36 — $ 49 $ — $ 49 $ — $ 49 Total VIE derivative assets $ 226 $ — $ 226 $ 226 $ — $ 239 $ — $ 239 $ — $ 239 Variable interest entities liabilities: Derivative liabilities: Interest rate swaps $ 1,197 $ — $ 1,197 $ — $ 1,197 $ 1,048 $ — $ 1,048 $ — $ 1,048 Total VIE derivative liabilities $ 1,197 $ — $ 1,197 $ — $ 1,197 $ 1,048 $ — $ 1,048 $ — $ 1,048
Summary of Location and Amount of Gains and Losses of Derivative Contracts	The following tables summarize the location and amount of gains and losses of derivative contracts in the Consolidated Statements of Total Comprehensive Income (Loss) for the years ended December 31, 2023, 2022 and 2021: Location of Gain (Loss) Recognized Amount of Gain (Loss) Recognized in Consolidated Statement of Total Comprehensive Income (Loss) – 2023 2022 2021 Non-VIE derivatives: Interest rate swaps Net gains (losses) on derivative contracts (1) 65 13 Warrants Net gains (losses) on derivative contracts — 1 — Futures contracts Net gains (losses) on derivative contracts — 62 9 Total Non-VIE derivatives (1) 129 22 Variable Interest Entities: Currency swaps Income (loss) on variable interest entities (1) 24 2 Interest rate swaps Income (loss) on variable interest entities (62) 541 (152) Total Variable Interest Entities (63) 565 (150) Total derivative contracts $ (64) $ 694 $ (128)
Summary of Notional Amounts of AFS's Trading Derivative Products	As of December 31, 2023 and 2022, the notional amounts of AFS's derivatives are as follows: Notional - December 31, Type of Derivative 2023 2022 Interest rate swaps—pay-fixed/receive-variable $ 141 $ 989 Interest rate swaps—receive-fixed/pay-variable 167 337 Warrants:
Variable Interest Entity [Member]
Summary of Notional Amounts of AFS's Trading Derivative Products	The notional for VIE derivatives outstanding as of December 31, 2023 and 2022, were as follows: Notional - December 31, Type of VIE Derivative 2023 2022 Interest rate swaps—receive-fixed/pay-variable $ 1,662 $ 1,573 Interest rate swaps—pay-fixed/receive-variable 864 887 Currency swaps 149 176

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
Intangible Assets (Tables)	Dec. 31, 2023
Statement of Financial Position [Abstract]
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	ntangible asset and accumulated amortization are included in the Consolidated Balance Sheets, as shown below. December 31, 2023 2022 Finite-lived Intangible Assets: Insurance intangible: Gross carrying value $ 1,258 $ 1,247 Accumulated amortization 1,013 981 Net insurance intangible asset 245 266 Other intangibles: Gross Carrying value 57 52 Accumulated amortization 10 6 Net other intangible assets 47 47 Total finite-lived intangible assets $ 292 $ 312 Indefinite-lived Intangible Assets: Insurance licenses $ 14 $ 14 Total intangible assets $ 307 $ 326
Finite-lived Intangible Assets Amortization Expense	Amortization expense is included in the Consolidated Statements of Total Comprehensive Income (Loss), as shown below. Year ended December 31, 2023 2022 2021 Insurance intangible $ 25 44 $ 52 Other intangibles 4 3 3 Total $ 29 $ 47 $ 55
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	The estimated future amortization expense for finite-lived intangible assets is as follows: Amortization Expense Insurance Intangible Asset (1) Other Intangible Assets (1) Total 2024 $ 26 $ 5 $ 30 2025 24 4 28 2026 22 4 26 2027 20 4 24 2028 18 4 22 Thereafter 136 26 162 (1)
Schedule of Goodwill	The following table presents a rollforward of goodwill at December 31, 2023 and 2022. December 31, 2023 2022 Beginning balance $ 61 $ 46 Business acquisitions 9 15 Impairments — — Ending balance $ 70 $ 61

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
Variable Interest Entities (Tables)	Dec. 31, 2023
Variable Interest Entity Not Primary Beneficiary Table [Line Items]
Schedule of Variable Interest Entities Assets and Liabilities [Table Text Block]	The following schedule details the components of Income (loss) on variable interest entities for the affected periods: Year ended December 31, 2023 2022 2021 Net change in fair value of VIE assets and liabilities reported under the fair value option $ 4 $ — $ 4 Less: Credit risk changes of fair value option long-term debt reported through other comprehensive income (loss) — (1) 1 Net change in fair value of VIE assets and liabilities reported in earnings under the fair value option 5 (1) 5 Investment income (loss) 7 (4) 6 Net realized investment gains (losses) on available-for-sale securities 1 2 2 Interest expense on long-term debt carried at par less unamortized cost (12) (12) (6) Other expenses (1) (1) (1) Gain (loss) from consolidating VIEs 4 37 — Income (loss) on variable interest entities $ 3 $ 21 $ 7
Variable Interest Entity Not Primary Beneficiary Table [Table Text Block]	The following table displays the carrying amount of the assets, liabilities and maximum exposure to loss of Ambac’s variable interests in non-consolidated VIEs resulting from financial guarantee and derivative contracts by major underlying asset classes, as of December 31, 2023 and 2022: December 31, 2023: December 31, 2022: Carrying Value of Assets and Liabilities Carrying Value of Assets and Liabilities Maximum (1) Insurance (2) Insurance (3) Net Derivative (Liabilities) (4) Maximum (1) Insurance (2) Insurance (3) Net Derivative (Liabilities) (4) Global structured finance: Mortgage-backed—residential $ 2,391 $ 135 $ 432 $ — $ 2,559 $ 266 $ 400 $ — Other consumer asset-backed 540 5 200 — 652 6 225 — Other 433 2 2 — 430 2 2 1 Total global structured finance 3,364 141 634 — 3,642 274 628 1 Global public finance 17,498 209 202 — 17,997 216 212 — Total $ 20,861 $ 351 $ 836 $ — $ 21,639 $ 490 $ 840 $ 1 (1) Maximum exposure to loss represents the maximum future payments of principal and interest on insured obligations and derivative contracts. Ambac’s maximum exposure to loss does not include the benefit of any financial instruments (such as reinsurance or hedge contracts) that Ambac may utilize to mitigate the risks associated with these variable interests. (2) Insurance assets represent the amount included in “Premium receivables” and “Subrogation recoverable” for financial guarantee insurance contracts on Ambac’s Consolidated Balance Sheets. (3) Insurance liabilities represent the amount included in “Loss and loss adjustment expense reserves” and “Unearned premiums” for financial guarantee insurance contracts on Ambac’s Consolidated Balance Sheets. (4) Net derivative assets (liabilities) represent the fair value recognized on interest rate swaps on Ambac’s Consolidated Balance Sheets.

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
Long-Term Debt (Tables)	Dec. 31, 2023
Debt Instrument [Line Items]
Schedule of Maturities of Long-term Debt [Table Text Block]	Aggregated annual maturities of non-VIE long-term debt obligations (based on scheduled maturity dates as further discussed below) are as follows: 2024 $ 519 (1) 2025 — 2026 — 2027 — 2028 — Thereafter 41 Total $ 560
Schedule of Long-term Debt Instruments	Long-term debt outstanding, excluding VIE long-term debt, was as follows: December 31, 2023 2022 Par Value Unamortized Discount Carrying Value Par Value Unamortized Discount Carrying Value Ambac Assurance: 5.1% Surplus Notes $ 519 $ (28) $ 491 $ 519 $ (42) $ 477 Tier 2 Notes — — — 146 — 146 Ambac UK Debt 41 (24) 17 41 (25) 16 Long-term debt $ 560 $ (52) $ 508 $ 706 $ (67) $ 639

Revenue from Contract with Cu_2

Revenue from Contract with Customer (Tables)	12 Months Ended
Revenue from Contract with Customer (Tables)	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table presents Insurance Distribution commission revenue recognized disaggregated by policy type for the years ended December 31, 2023, 2022 and 2021 : Year ended December 31, 2023 2022 2021 Employer stop loss $ 11 $ 9 $ 8 Affinity products 22 19 18 Commercial auto 12 2 — Marine 3 — — Professional liability 3 — — Other 1 — — Total 51 $ 31 $ 26
Contract with Customer, Contract Asset, Contract Liability, and Receivable	The balances of receivables, contract assets and contract liabilities with customers were as follows: December 31, 2023 2022 Receivables $ 10 $ 7 Contract assets 95 5 Contract liabilities 1 1

Comprehensive Income (Tables)

Comprehensive Income (Tables)	12 Months Ended
Comprehensive Income (Tables)	Dec. 31, 2023
Equity [Abstract]
Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Income	The following tables detail the changes in the balances of each component of accumulated other comprehensive income for the affected periods: Year Ended December 31, 2023: Year ended December 31, 2022: Unrealized Gains (Losses) on Available- for Sale Securities (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency Translation (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Unrealized Gains (Losses) on Available- for Sale Securities (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency Translation (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Beginning Balance $ (71) $ 3 $ (184) $ (1) $ (253) $ 154 $ 4 $ (100) $ (1) $ 58 Other comprehensive income (loss) before reclassifications 31 3 40 — 74 (211) — (85) — (296) Amounts reclassified from accumulated other comprehensive income (loss) 21 (1) — — 19 (14) (1) — — (15) Net current period other comprehensive income (loss) 51 2 40 — 93 (225) (1) (85) — (310) Ending balance $ (20) $ 5 $ (144) $ (1) $ (160) $ (71) $ 3 $ (184) $ (1) $ (253) (1) All amounts are net of tax and noncontrolling interest. Amounts in parentheses indicate reductions to Accumulated Other Comprehensive Income. (2) Represents the changes in fair value attributable to instrument-specific credit risk of liabilities for which the fair value option is elected.
Schedule of Amounts Reclassed Out of Each Component of Accumulated Other Comprehensive Income	The following table details the significant amounts reclassified from each component of accumulated other comprehensive income, shown in the above rollforward tables, for the affected periods: Details about Accumulated Other Amount Reclassified from Accumulated Affected Line Item in the Year Ended December 31, 2023 2022 Unrealized Gains (Losses) on Available-for-Sale Securities (1) $ 22 $ (17) Net realized investment gains (losses) (2) 3 Provision for income taxes $ 21 $ (14) Net of tax and noncontrolling interest Amortization of Postretirement Benefit Prior service cost $ (1) $ (1) Other income Actuarial gains (losses) (1) — Other income (1) (1) Total before tax — — Provision for income taxes $ (1) $ (1) Net of tax and noncontrolling interest Credit Risk Changes of Fair Value Option Liabilities $ — $ — Credit risk changes of fair value option liabilities — — Provision for income taxes — — Net of tax and noncontrolling interest Total reclassifications for the period $ 19 $ (15) Net of tax and noncontrolling interest (1) Net unrealized investment gains (losses) on available for sale securities are included in Ambac's Consolidated Statements of Comprehensive Income as a component of Accumulated Other Comprehensive Income. Changes in these amounts include reclassification adjustments to exclude from "Other comprehensive income (loss)" those items that are included as part of "Net income" for a period that has been part of "Other comprehensive income (loss)" in earlier periods.

Net Income Per Share (Tables)

Net Income Per Share (Tables)	12 Months Ended
Net Income Per Share (Tables)	Dec. 31, 2023
Earnings Per Share [Abstract]
Reconciliation of Common Shares Used for Basic and Diluted Earnings Per Share	The following table provides a reconciliation of the common shares used for basic net income per share to the diluted shares used for diluted net income per share: Year Ended December 31, 2023 2022 2021 Basic weighted average shares outstanding 45,636,649 45,719,906 46,535,001 Effect of potential dilutive shares (1) : Warrants — — — Restricted stock units 164,752 144,194 — Performance stock units (2) 739,305 550,730 — Diluted weighted average shares outstanding 46,540,706 46,414,830 46,535,001 Anti-dilutive shares excluded from the above reconciliation Warrants — 4,877,617 4,877,653 Restricted stock units 135,058 177,119 475,333 Performance stock units (2) — — 700,915 (1) For the year ended December 31, 2021, Ambac had a net loss and accordingly excluded all potentially dilutive securities from the determination of diluted loss per share as their impact was anti-dilutive. (2) Performance stock units are reflected based on the performance metrics through the balance sheet date. Vesting of these units is contingent upon meeting certain performance metrics. Although a portion of these performance metrics have been achieved as of the respective period end, it is possible that awards may no longer meet the metric at the end of the performance period.
Schedule of Earnings Per Share, Basic and Diluted	The following table provides a reconciliation of net income attributable to common stockholders to the numerator in the basic and diluted earnings per share calculation, together with the resulting earnings per share amounts: Year ended December 31, 2023 2022 2021 Net income (loss) attributable to common stockholders $ 4 $ 522 $ (17) Adjustment to redemption value (ASC 480) 5 3 (12) Numerator of basic and diluted EPS $ 8 $ 525 $ (28) Per Share: Basic $ 0.18 $ 11.48 $ (0.61) Diluted $ 0.18 $ 11.31 $ (0.61)

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Major Jurisdictions	The following are the major jurisdictions in which Ambac and its subsidiaries operate and the earliest tax years subject to examination: Jurisdiction Tax Year United States 2010 New York State 2013 New York City 2018 United Kingdom 2020 Italy 2019
Significant Portions of Deferred Tax Liabilities and Deferred Tax Assets	The tax effects of temporary differences that give rise to significant portions of the deferred tax liabilities and deferred tax assets at December 31, 2023 and 2022, are presented below: December 31, 2023 2022 Deferred tax liabilities: Insurance intangible $ 51 $ 56 Unearned premiums and credit fees 23 24 Variable interest entities — 4 Other 3 1 Total deferred tax liabilities 77 85 Deferred tax assets: Net operating loss carryforward 714 725 Interest expense carryforward 58 66 Loss reserves 42 38 Debentures 22 15 State capital loss carryforward 8 8 Compensation 5 6 Investments — 6 Other 4 4 Subtotal deferred tax assets 853 867 Valuation allowance 795 796 Total deferred tax assets 58 70 Net deferred tax liability $ 19 $ 15
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]	U.S. and foreign components of pre-tax income (loss) were as follows: Year Ended December 31, 2023 2022 2021 U.S. $ (29) $ 511 $ (32) Foreign 41 13 34 Total $ 12 $ 525 $ 2
Schedule of Components of Income Tax Expense (Benefit)	The components of the provision (benefit) for income taxes were as follows: Year Ended December 31, 2023 2022 2021 Current taxes U.S. state and local $ 1 $ — $ 2 Foreign 8 7 10 Total current taxes 8 6 12 Deferred taxes Domestic (2) — — Foreign 1 (4) 6 Total deferred taxes $ (1) $ (4) $ 6 Provision for income taxes $ 7 $ 2 $ 18
Schedule Of Income Taxes Charged Credited Directly To Equity	The total effect of income taxes on net income and stockholders’ equity for the years ended December 31, 2023, 2022 and 2021 is as follows: Year Ended December 31, 2023 2022 2021 Total income taxes charged to net income $ 7 $ 2 $ 18 Income taxes charged (credited) to stockholders’ equity: Unrealized gains (losses) on investment securities, including foreign exchange 12 (47) (3) Change in retirement benefits (1) — — Credit Risk Changes to Fair Value Options — — — Valuation allowance to equity (9) 41 1 Total charged to stockholders’ equity: 2 (6) (2) Total effect of income taxes $ 9 $ (4) $ 16
Schedule of Effective Income Tax Rate Reconciliation	Year Ended December 31, 2023 2022 2021 Total income taxes charged to net income $ 7 $ 2 $ 18 Income taxes charged (credited) to stockholders’ equity: Unrealized gains (losses) on investment securities, including foreign exchange 12 (47) (3) Change in retirement benefits (1) — — Credit Risk Changes to Fair Value Options — — — Valuation allowance to equity (9) 41 1 Total charged to stockholders’ equity: 2 (6) (2) Total effect of income taxes $ 9 $ (4) $ 16 Reconciliation of U.S. Federal Statutory Income Tax Rate to Actual Income Tax Rate The tax provisions in the accompanying Consolidated Statements of Total Comprehensive Loss reflect effective tax rates differing from prevailing Federal corporate income tax rates. The following is a reconciliation of these differences: Year Ended December 31, 2023 2022 2021 Tax on income (loss) at statutory rate $ 3 21 % $ 110 21 % $ — 21 % Changes in expected tax resulting from: Tax-exempt interest — — % (1) — % (2) (114) % Foreign taxes 9 70 % 4 1 % 8 448 % State Income Taxes — (1) % (1) — % 14 794 % Return to Provision 15 118 % — — % — — % Variable Interest Entities (24) (197) % 25 5 % — — % Valuation allowance 2 13 % (131) (25) % (4) (230) % Other, net 4 35 % (4) (1) % 1 72 % Tax expense on income (loss) $ 7 60 % $ 2 1 % $ 18 991 %
Schedule of Net Operating Loss And Tax Credit Carryovers	As of December 31, 2023, the Company has (i) $3,400 of NOLs, which if not utilized will begin expiring in 2030, and will fully expire in 2042, and (ii) $274 of interest expense tax deduction carryover, which has an indefinite carryforward period but is limited in any particular year based on certain provisions.

Employment Benefit Plans (Table

Employment Benefit Plans (Tables)	12 Months Ended
Employment Benefit Plans (Tables)	Dec. 31, 2023
Postemployment Benefits [Abstract]
Schedule of Expected Benefit Payments [Table Text Block]	The following table sets forth projected benefit payments from Ambac’s postretirement plan over the next ten years for current retirees: 2024 $ — 2025 — 2026 1 2027 1 2028 1 Thereafter 3 Total $ 6
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable [Table Text Block]	The amount of stock-based compensation expense and corresponding after-tax expense are as follows: Year Ended December 31, 2023 2022 2021 Restricted stock units $ 5 $ 5 $ 5 Performance awards 12 12 10 Total stock-based compensation $ 17 $ 17 $ 14 Total stock-based compensation (after-tax) $ 17 $ 17 $ 11
Share-based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block]	A summary of RSU activity for 2023 is as follows: Shares Weighted Average Grant Date Fair Value Per Share Outstanding at beginning of period 923,250 $ 15.94 Granted 415,416 15.72 Delivered or returned to plan (1) (300,164) 16.28 Forfeited (2,163) 16.97 Outstanding at end of period 1,036,339 $ 15.75 (1) When restricted stock unit awards issued by Ambac become taxable compensation to employees, shares may be withheld to cover the employee’s withholding taxes. For the year ended December 31, 2023, Ambac withheld 49,870 shares from employees that settled restricted stock units to meet the required tax withholdings.
Schedule of Nonvested Performance-based Units Activity [Table Text Block]	A summary of PSU activity for 2023 is as follows: Shares Weighted Average Outstanding at beginning of period 918,951 $ 15.67 Granted (1) 479,079 17.72 Delivered (2) (525,212) 18.90 Forfeited (1,289) 17.72 Performance adjustment (3) 147,542 19.50 Outstanding at end of period 1,019,071 $ 15.52 (1) Represents performance share units at 100% of units granted for LTIP Awards. (2) Reflects the number of performance shares attributable to the performance goals attained over the completed performance period and for which service conditions have been met. When performance stock unit awards issued by Ambac become taxable compensation to employees, shares may be withheld to cover the employee’s withholding taxes. For the year ended December 31, 2023, Ambac withheld 231,645 of shares from employees that settled performance based restricted stock units to meet the required tax withholdings. (3) Represents the number of additional shares issued for awards granted in 2020 as a result of actual performance during the performance period.

Leases (Tables)

Leases (Tables)	12 Months Ended
Leases (Tables)	Dec. 31, 2023
Lessor, Operating Lease, Payments to be Received, Maturity [Table Text Block]	Future undiscounted lease payments to be received are as follows: As of December 31, 2023 Operating 2024 $ 1 2025 1 2026 1 2027 1 2028 1 Thereafter 1 Total lease receipts $ 8
Lease, Cost [Table Text Block]	The components of lease costs, net of sub-lessor income, is as follows: Year Ended December 31, 2023 2022 Operating lease cost $ 4 $ 4 Short-term lease cost — — Variable lease cost 1 — Sublease income (1) (1) Total lease cost $ 4 $ 4 Ambac is required to make variable lease payments under certain leases which primarily relates to variable costs of the lessor, such as taxes, insurance, maintenance and electricity. Supplemental information related to leases is as follows: Year Ended December 31, 2023 2022 Cash paid for amounts included in the measurement of operating lease liabilities $ 5 $ 5 Right-of-use assets obtained in exchange for operating lease liabilities (non-cash) 1 — Supplemental balance sheet information related to leases is as follows: December 31, 2023 2022 Operating leases: Operating lease right of use assets $ 19 $ 21 Operating lease liabilities 22 25 Weighted average remaining lease term: Operating leases 6.1 years 6.8 years Weighted average discount rate: Operating leases 7.9 % 7.8 %
Cash Flow, Supplemental Disclosures [Text Block]	Supplemental information related to leases is as follows: Year Ended December 31, 2023 2022 Cash paid for amounts included in the measurement of operating lease liabilities $ 5 $ 5 Right-of-use assets obtained in exchange for operating lease liabilities (non-cash) 1 —
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	Future undiscounted lease payments, gross of sublease receipts, to be made are as follows: As of December 31, 2023 Operating 2024 $ 4 2025 5 2026 5 2027 5 2028 5 Thereafter 5 Total lease payments 28 Less: imputed interest (6) Total $ 22
Schedule of Supplemental Cash Flow Information [Table Text Block]	Supplemental Disclosure of Cash Flow Information Year Ended December 31, 2023 2022 2021 Cash paid during the period for: Income taxes $ 11 $ 6 $ 15 Interest on long-term debt 50 283 80 Non-cash investing and financing activities: Exchange of investments in Puerto Rico bonds for new securities issued in the restructuring transactions — 185 — Decrease in long-term debt as a result of surplus notes exchanges — — 71 Securities acquired (transferred) in transactions related to Puerto Rico restructurings (1) 508 — Loans acquired through financial guarantee subrogation — 20 — VIE long-term debt issued related to Puerto Rico restructurings — 583 — Decrease in VIE loans as a result of de-consolidations 133 — — Decrease in VIE long-term debt as a result of de-consolidations 133 — — Increase in VIE long-term debt as a result of consolidations 89 — — December 31, 2023 2022 2021 Reconciliation of cash, cash equivalents, and restricted cash reported within the Consolidated Balance Sheets to the Consolidated Statements of Cash Flow: Cash and cash equivalents $ 16 $ 31 $ 17 Restricted cash 12 14 5 Variable Interest Entity Restricted cash 246 17 2 Total cash, cash equivalents, and restricted cash shown on the Consolidated Statements of Cash Flows 274 61 23

Background and Business Descr_3

Background and Business Description Rehabilitation Exit Support Agreement (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Apr. 29, 1991	Dec. 31, 2017	Dec. 31, 2023	Dec. 31, 2022	Apr. 30, 2013
Preferred Stock, Shares Outstanding			0	0
Common stock, shares authorized			130,000,000	130,000,000
Common Stock, Par or Stated Value Per Share					$ 0.01
Preferred stock, shares authorized			20,000,000	20,000,000
Preferred Stock, Par or Stated Value Per Share			$ 0.01		$ 0.01
Common stock, shares issued			46,659,144	46,658,990
Common Stock Voting Restrictions	10%
Common Stock Voting Restriction Less One Vote	10%
Common Stock Transfer Restrictions	5%
Common Stock Additional Transfer Restrictions		5%
Stockholders' Equity Attributable to Noncontrolling Interest			$ 53	$ 53
Ambac Assurance Corporation [Member]
Preferred Stock, Shares Outstanding			4,596	4,596
Preferred Stock, Liquidation Preference, Value			$ 115	$ 115
Stockholders' Equity Attributable to Noncontrolling Interest			$ 51

Background and Business Descr_4

Background and Business Description Stipulation and Order (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
AAC Transaction Amount Requiring OCI Approval	$ 100

Background and Basis of Present

Background and Basis of Presentation - Surplus Note Exchange (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Insurance [Line Items]
Net realized gains on extinguishment of debt	$ 0	$ 81	$ 33
Realized Investment Gains (Losses)	(22)	31	7
Parent Company [Member]
Insurance [Line Items]
Realized Investment Gains (Losses)	$ 0	(14)	$ (5)
5.1% Surplus Notes, General Account, Due 2020 [Member]
Insurance [Line Items]
Net realized gains on extinguishment of debt		$ 134
Ambac Assurance Corporation [Member] \| 5.1 % Surplus Notes Due 2020 [Member]
Insurance [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.10%	5.10%

Background and Business Descr_5

Background and Business Description AMPS Exchange (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Stockholders' Equity Attributable to Noncontrolling Interest	$ 53	$ 53
Preferred Stock, Shares Outstanding	0	0
Ambac Assurance Corporation [Member]
Preferred Stock, Liquidation Preference, Value	$ 115	$ 115
Stockholders' Equity Attributable to Noncontrolling Interest	$ 51
Preferred Stock, Shares Outstanding	4,596	4,596

Background and Business Descr_6

Background and Business Description - Additional Information (Detail)		12 Months Ended
	Apr. 29, 1991	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($)	Dec. 31, 2017	Jul. 06, 2021 USD ($)	Apr. 30, 2013 $ / shares
Background And Basis Of Presentation [Line Items]
Common stock, shares authorized \| shares		130,000,000	130,000,000
Common Stock, Par or Stated Value Per Share \| $ / shares							$ 0.01
Preferred stock, shares authorized \| shares		20,000,000	20,000,000
Preferred Stock, Par or Stated Value Per Share \| $ / shares		$ 0.01					$ 0.01
Common stock, shares issued \| shares		46,659,144	46,658,990
Common Stock Voting Restriction Less One Vote	10%
Common Stock Transfer Restrictions	5%
Common Stock Additional Transfer Restrictions					5%
Financial Guarantee Insurance Contracts, Accelerated Premium Revenue, Amount \| $		$ 0	$ 8,000,000	$ 1,000,000
Number of Admitted Carriers Owned \| $		5
Number of Reportable Segments		3
Number of Admitted Carriers Acquired in 2022		3
LIBOR + 4.5% Senor Secured Notes Due 2026 \| London Interbank Offered Rate (LIBOR) [Member]
Background And Basis Of Presentation [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						4.50%
Sitka Holdings, LLC \| LIBOR + 4.5% Senor Secured Notes Due 2026
Background And Basis Of Presentation [Line Items]
Debt Instrument, Face Amount \| $						$ 1,175,000,000

Background and Business Descr_7

Background and Business Description - Redemption of Notes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net realized gains on extinguishment of debt	$ 0	$ 81	$ 33
5.1% Surplus Notes, General Account, Due 2020 [Member]
Net realized gains on extinguishment of debt		$ 134
Nomura Credit & Capital, Inc.
Proceeds from Legal Settlements	140
Sitka AAC Note \| Ambac Assurance Corporation [Member]
Repayments of Long-term Debt	$ 1,218
Long-term Debt, Repayment, Premium Paid on Principal	103%
Net realized gains on extinguishment of debt	$ 53
Tier 2 Notes [Member] \| Ambac Assurance Corporation [Member]
Repayments of Long-term Debt	$ 213

Background and Business Descr_8

Background and Business Description - Settlement of RMBS Litigation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Gain (Loss) Related to Litigation Settlement		$ 126	$ 0
Loss Reserves [Member]
Gain (Loss) Related to Litigation Settlement	$ 362
Litigation Recoveries
Gain (Loss) Related to Litigation Settlement	126
Gain (loss) on extinguishment of debt
Gain (Loss) Related to Litigation Settlement	(53)
Gain (Loss) on Investments [Member]
Gain (Loss) Related to Litigation Settlement	5
R&W value
Loss and Loss Benjefit Relating to R&W Recoveries	123
Bank of America
Proceeds from Legal Settlements	1,840
Gain (Loss) Related to Litigation Settlement	440
Nomura Credit & Capital, Inc.
Proceeds from Legal Settlements	$ 140

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Apr. 29, 1991	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2017	Dec. 31, 2020	Apr. 30, 2013
Finite-Lived Intangible Assets [Line Items]
Operating Lease, Liability		$ 22	$ 25
Income Taxes Paid		$ 11	$ 6	$ 15
Common Stock Voting Restrictions	10%
Common Stock, Par or Stated Value Per Share							$ 0.01
Preferred stock, shares authorized		20,000,000	20,000,000
Preferred Stock, Par or Stated Value Per Share		$ 0.01					$ 0.01
Common stock, shares issued		46,659,144	46,658,990
Warrant Exercised During Period Shares		1,503	0	132
Common Stock Transfer Restrictions	5%
Common Stock Additional Transfer Restrictions					5%
Restricted Cash		$ 12	$ 14	$ 5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		274	61	23		$ 35
Investment income due and accrued		$ 14	$ 10
Accrued Investment Interest Receivable Write-off Period in Days		90
Weighted average period of future premiums		7 years 8 months 12 days	8 years
Estimated Future Premium Payments Weighted Average Discounted Rate		3.20%	3%
Investment income due and accrued		$ 14	$ 10
CECL Securities Factor for Consideration		20%
Specialty Property & Casualty Program
Finite-Lived Intangible Assets [Line Items]
Reinsurance, Reinsured Risk, Percentage		70%
Xchange
Finite-Lived Intangible Assets [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired		80%
All Trans
Finite-Lived Intangible Assets [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired		85%
Capacity Marine
Finite-Lived Intangible Assets [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired		80%
Riverton
Finite-Lived Intangible Assets [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired		80%
Minimum [Member] \| Furniture and Fixtures [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		3 years
Maximum [Member] \| Furniture and Fixtures [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		5 years
Long-term Debt [Member]
Finite-Lived Intangible Assets [Line Items]
Interest Paid, Including Capitalized Interest, Operating and Investing Activities		$ 50	283	80
Variable Interest Entity, Primary Beneficiary [Member]
Finite-Lived Intangible Assets [Line Items]
Restricted Cash		$ 246	$ 17	$ 2
Estimated Future Premium Payments Weighted Average Discounted Rate		6.30%	6.80%

Basis of Presentation and Sig_5

Basis of Presentation and Significant Accounting Policies FX gain (loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Foreign Currency Transaction Gain (Loss), before Tax	$ (3)	$ 11	$ (7)
Gain (Loss) on Investments [Member]
Foreign Currency Transaction Gain (Loss), before Tax	$ (4)	$ 14	$ (5)

Basis of Presentation and Sig_6

Basis of Presentation and Significant Accounting Policies Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Intangible assets, less accumulated amortization	$ 307	$ 326
Goodwill, Impaired, Accumulated Impairment Loss	0	$ 0
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)	0
Impairment of Intangible Assets, Finite-lived	$ 0

Basis of Presentation and Sig_7

Basis of Presentation and Significant Accounting Policies Noncontrolling Interest (Details) $ in Millions	6 Months Ended		12 Months Ended
	Dec. 31, 2023 USD ($) shares	Jun. 30, 2023	Dec. 31, 2023 USD ($) shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 USD ($)
Stockholders' Equity Attributable to Noncontrolling Interest	$ 53		$ 53	$ 53
Preferred Stock, Shares Outstanding \| shares	0		0	0
Redeemable Noncontrolling Interest, Equity, Carrying Amount	$ 17		$ 17	$ 20	$ 18
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value	2		2	5
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest			1	1
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders			(2)	(1)
Temporary Equity, Accretion to Redemption Value, Adjustment			(5)	$ (3)
AMPS Shares Purchased				(905)
AMPS Gain Based on Carry Value				$ 1
AMPS Purchase Cash Paid				$ 8
Ambac Assurance Corporation [Member]
Stockholders' Equity Attributable to Noncontrolling Interest	$ 51		$ 51
Preferred Stock, Shares Outstanding \| shares	4,596		4,596	4,596
Preferred Stock, Liquidation Preference, Value	$ 115		$ 115	$ 115
London Interbank Offered Rate (LIBOR) [Member]
Dividend Rate on Auction Rate Preferred Shares		20,000%
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Dividend Rate on Auction Rate Preferred Shares	11.448%

Basis of Presentation and Sig_8

Basis of Presentation and Significant Accounting Policies Adoption of New Accounting Standards (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Operating Lease, Liability	$ 22	$ 25

Basis of Presentation and Sig_9

Basis of Presentation and Significant Accounting Policies Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes Paid	$ 11	$ 6	$ 15
Restricted Cash	12	14	5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	274	61	23	$ 35
Decrease in long-term debt as a result of surplus notes exchanges	0	0	71
Securities acquired in transactions related to Puerto Rico restructurings	(1)	508	0
Loans acquired through financial guarantee subrogation	0	20	0
VIE long-term debt issued related to Puerto Rico restructurings	0	583	0
Decrease in VIE loans as a result of de-consolidations	133	0	0
Decrease in VIE long-term debt as a result of de-consolidations	133	0	0
Increase in VIE long-term debt as a result of consolidations	89	0	0
Non Cash Exchange of Puerto Rico Bonds	0	185	0
Long-term Debt [Member]
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	50	283	80
Variable Interest Entity, Primary Beneficiary [Member]
Restricted Cash	$ 246	$ 17	$ 2

Basis of Presentation and Si_10

Basis of Presentation and Significant Accounting Policies Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Restricted Cash	$ 12	$ 14	$ 5
Insurance Distribution
Restricted Cash	$ 12	$ 14

Segment Reporting (Details)

Segment Reporting (Details) - USD ($) $ in Millions	12 Months Ended
Segment Reporting (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Premiums Earned, Net	$ 78	$ 56	$ 47
Insurance Commissions and Fees	51	31	26
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	8	3	0
Net Investment Income	140	17	139
Realized Investment Gains (Losses)	(22)	31	7
Derivative, Gain (Loss) on Derivative, Net	(1)	129	22
Net realized gains on extinguishment of debt	0	81	33
Other income Items	15	31	8
Losses and loss adjustment expenses		(396)	(88)
Deferred Policy Acquisition Costs, Amortization Expense	11	3	1
Insurance Commissions	29	18	15
Operating Expenses	155	139	110
Depreciation	2	2	2
Amortization of intangible assets	29	47	55
Interest Expense	64	168	187
Benefits, Losses and Expenses	257	(20)	281
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	12	525	2
Income Tax Expense (Benefit)	7	2	18
Assets	8,428	7,973	12,303
Gain (Loss) Related to Litigation Settlement		126	0
Revenues	269	505	282
Policyholder Benefits and Claims Incurred, Net	(33)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	5	522	(16)
Legacy Financial Guarantee
Premiums Earned, Net	26	42	46
Net Investment Income	127	12	138
Realized Investment Gains (Losses)	(23)	32	3
Derivative, Gain (Loss) on Derivative, Net	(1)	128	22
Net realized gains on extinguishment of debt		81	33
Other income Items	15	30	8
Losses and loss adjustment expenses		(406)	(89)
Deferred Policy Acquisition Costs, Amortization Expense	0	0	0
Operating Expenses	106	102	77
Depreciation	1	2	2
Amortization of intangible assets	25	44	52
Interest Expense	64	168	187
Benefits, Losses and Expenses	127	(89)	230
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	17	540	20
Income Tax Expense (Benefit)	8	3	16
Assets	7,537	7,292	11,871
Gain (Loss) Related to Litigation Settlement		126	0
Revenues	144	451	250
Policyholder Benefits and Claims Incurred, Net	(69)	(406)	(89)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	9	537	4
Specialty Property & Casualty Program
Premiums Earned, Net	52	14	1
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	8	3	0
Net Investment Income	4	2	1
Realized Investment Gains (Losses)	0	0	0
Other income Items	0	0	0
Losses and loss adjustment expenses		9	0
Deferred Policy Acquisition Costs, Amortization Expense	11	3	0
Operating Expenses	16	13	9
Depreciation	0	0	0
Benefits, Losses and Expenses	64	25	9
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	0	(6)	(8)
Income Tax Expense (Benefit)	0	0	0
Assets	523	316	156
Revenues	64	18	2
Policyholder Benefits and Claims Incurred, Net	37
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	0	(6)	(8)
Insurance Distribution
Insurance Commissions and Fees	51	31	26
Net Investment Income	0
Realized Investment Gains (Losses)
Other income Items	0	1	0
Insurance Commissions	29	18	15
Operating Expenses	11	6	5
Depreciation	0	0	0
Amortization of intangible assets	4	3	3
Benefits, Losses and Expenses	44	27	22
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	7	5	4
Income Tax Expense (Benefit)	0	0	0
Assets	155	138	93
Revenues	52	31	26
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	7	5	4
Corporate and Other
Net Investment Income	9	3	1
Realized Investment Gains (Losses)	0	0	4
Derivative, Gain (Loss) on Derivative, Net	0	1
Other income Items	0	0	0
Operating Expenses	21	17	19
Depreciation	0	0	0
Benefits, Losses and Expenses	22	17	19
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(13)	(14)	(15)
Income Tax Expense (Benefit)	(1)	0	2
Assets	213	226	182
Revenues	9	4	5
Surplus Notes			90
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (11)	$ (13)	$ (17)

Investments - Summary of Amorti

Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments (Detail) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	$ 2,197,000,000	$ 2,041,000,000
Gross Unrealized Gains	40,000,000	31,000,000
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71,000,000	106,000,000
Available-for-sale Securities	1,710,000,000	1,395,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	3,000,000	0
Debt Securities, Available-for-Sale, Current	2,162,000,000	1,966,000,000
Fixed Income Investments And Other Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	1,744,000,000	1,469,000,000
Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	72,000,000	44,000,000
Gross Unrealized Gains	1,000,000	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1,000,000	2,000,000
Available-for-sale Securities	72,000,000	43,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Corporate Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	785,000,000	659,000,000
Gross Unrealized Gains	4,000,000	1,000,000
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	44,000,000	63,000,000
Available-for-sale Securities	745,000,000	598,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Security, Government, Non-US [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	105,000,000	85,000,000
Gross Unrealized Gains	1,000,000	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	6,000,000	9,000,000
Available-for-sale Securities	100,000,000	76,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
U.S. Government Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	85,000,000	68,000,000
Gross Unrealized Gains	1,000,000	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	4,000,000	4,000,000
Available-for-sale Securities	82,000,000	65,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	239,000,000	230,000,000
Gross Unrealized Gains	28,000,000	28,000,000
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	14,000,000	19,000,000
Available-for-sale Securities	250,000,000	238,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	3,000,000	0
Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	139,000,000	141,000,000
Gross Unrealized Gains	1,000,000	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1,000,000	4,000,000
Available-for-sale Securities	139,000,000	137,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	301,000,000	227,000,000
Gross Unrealized Gains	3,000,000	2,000,000
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1,000,000	5,000,000
Available-for-sale Securities	303,000,000	224,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	426,000,000	507,000,000
Gross Unrealized Gains	0	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	0
Available-for-sale Securities	426,000,000	507,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	19,000,000	15,000,000
Gross Unrealized Gains	0	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	0
Available-for-sale Securities	19,000,000	0
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Available-for-sale, Debt Securities		15,000,000
Collateralized Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	19,000,000
Fixed Income Investments And Other Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	2,170,000,000	1,977,000,000
Gross Unrealized Gains	40,000,000	31,000,000
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71,000,000	106,000,000
Available-for-sale Securities	2,135,000,000	1,902,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	3,000,000	0
Collateral Pledged [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Gains	0	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	0
Available-for-sale Securities	27,000,000	64,000,000
Collateral Pledged [Member] \| Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	27,000,000	64,000,000
Gross Unrealized Gains	0	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	0
Available-for-sale Securities	27,000,000	64,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Asset Pledged as Collateral [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	27,000,000	64,000,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 0	$ 0

Investments - Summary of Amor_2

Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments Held by Successor Ambac, by Contractual Maturity (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Due in one year or less	$ 544
Amortized Cost, Due after one year through five years	581
Amortized Cost, Due after five years through ten years	293
Amortized Cost, Due after ten years	80
Amortized Cost, Total	1,500
Fixed income securities, amortized cost	2,197	$ 2,041
Estimated Fair Value, Due in one year or less	544
Estimated Fair Value, Due after one year through five years	560
Estimated Fair Value, Due after five years through ten years	271
Estimated Fair Value, Due after ten years	76
Estimated Fair Value due, Total	1,451
Debt Securities, Available-for-sale	1,710	1,395
Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	239	230
Debt Securities, Available-for-sale	250	238
Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	139	141
Debt Securities, Available-for-sale	139	137
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Fixed income securities, amortized cost	301	227
Debt Securities, Available-for-sale	$ 303	$ 224

Investments - Summary of Gross

Investments - Summary of Gross Unrealized Losses and Fair Values of Ambac's Available-for-Sale Investments (Detail) $ in Millions	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ 4	$ 53
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	844	400
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	68	53
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71	106
Debt Securities Accumulated Gross Unrealized Loss Before Tax Included Pledged Securities		106
Debt Securities, Available for sale, Unrealized Loss Position, Including Pledged Securities	1,032	1,269
Debt Securities , Available for sale, Continuous Unrealized Loss Position,	187
Available-for-sale Securities	$ 1,710	1,395
Average Percentage Loss Versus Amortized Cost	7%
Average Percentage of Unrealized Loss Versus Amortized Cost for Below Investment Grade Securities	5%
Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	$ 1	2
Available-for-sale Securities	72	43
US Government Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	4	4
Available-for-sale Securities	82	65
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	44	63
Available-for-sale Securities	745	598
Debt Security, Government, Non-US [Member]
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	6	9
Available-for-sale Securities	100	76
Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	14	19
Available-for-sale Securities	250	238
Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1	4
Available-for-sale Securities	139	137
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1	5
Available-for-sale Securities	303	224
Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	4	78
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	8
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	4	86
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	0
Available-for-sale Securities	$ 426	507
Ambac Insured Securities \| Parsed Fixed Income Securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions	4,000
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	$ 0	0
Available-for-sale Securities	19	0
Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	184	791
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	4	53
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	844	392
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	68	53
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,028	1,183
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71	106
Fixed Income Securities [Member] \| Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	7	21
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	16	7
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	1	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	23	28
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1	2
Fixed Income Securities [Member] \| US Government Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	27	40
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	37	19
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	2	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	63	58
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	4	4
Fixed Income Securities [Member] \| US Government Debt Securities [Member] \| Asset Pledged as Collateral [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities Available For Sale Continuous Unrealized Loss Position Less Than 12 Months Including Pledged Securities		869
Fixed Income Securities [Member] \| Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	75	280
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2	21
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	509	279
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	43	42
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	584	559
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	$ 44	63
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions	662,000
Fixed Income Securities [Member] \| Corporate Debt Securities [Member] \| External Credit Rating, Investment Grade
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	$ 44
Fixed Income Securities [Member] \| Corporate Debt Securities [Member] \| External Credit Rating, Non Investment Grade [Member]
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1
Fixed Income Securities [Member] \| Debt Security, Government, Non-US [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	8	27
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	56	47
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	6	7
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	64	73
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	6	9
Fixed Income Securities [Member] \| Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	6	132
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	19
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	98	0
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	14	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	104	132
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	14	19
Fixed Income Securities [Member] \| Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	1	90
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	93	36
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	1	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	95	126
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1	4
Fixed Income Securities [Member] \| Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	57	198
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	35	5
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	1	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	92	203
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1	5
Fixed Income Securities [Member] \| Ambac Insured Securities
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	$ 13
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions	11,000
Dbt Securities Available for Sale Unrealized Loss Measured as a Percent of Amortized Cost	14%
Fixed Income Securities [Member] \| Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 3	3
Fixed Income Securities [Member] \| Collateralized Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	3	3
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	0
Collateral Pledged [Member]
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	0
Available-for-sale Securities	27	64
Collateral Pledged [Member] \| Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	0
Available-for-sale Securities	$ 27	$ 64

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Reported Value Measurement [Member]
Investment [Table]
Other Investments	$ 77	$ 61
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	28	44
Reported Value Measurement [Member] \| Interest Rate Contract [Member]
Investment [Table]
Other Investments	39	0
Reported Value Measurement [Member] \| Equity [Member]
Investment [Table]
Other Investments	38	53
Reported Value Measurement [Member] \| Convertibles and Bonds with Warrants Attached
Investment [Table]
Other Investments	0	8
Other Investments	475	568
Securities fair value	24	23
Fair Value of Securities Deposited in Connection wtih Letter of Credit	1
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	0
Equity Securities Excluded From Fair Value	13	12
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	274	61	$ 23	$ 35
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	28	44
Insurance Distribution
Investment [Table]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	2	0
Real Estate [Member]
Investment [Table]
Other Investments	21	22
Hedge Funds, Multi-strategy [Member]
Investment [Table]
Other Investments	112	186
Interest Rate Contract [Member]
Investment [Table]
Other Investments	85	80
Illiquid Investments [Member]
Investment [Table]
Other Investments	84	84
Insurance Linked [Member]
Investment [Table]
Other Investments	1	1
Equity [Member]
Investment [Table]
Other Investments	38	64
Credit Index Product [Member]
Investment [Table]
Other Investments	52	63
Equity investments in pooled funds [Member]
Investment [Table]
Other Investments	463	556
Private Equity Funds, US
Investment [Table]
Other Investments	70	47
Convertibles and Bonds with Warrants Attached
Investment [Table]
Other Investments	0	8
Investment Portfolio [Member]
Investment [Table]
Fair Value of Cash and Securities Pledged to Derivative Counterparties	27	$ 64
Commitments [Member] \| Private Equity Funds
Investment [Table]
Other Investments	$ 41

Investments - Summary of Amount

Investments - Summary of Amounts Included in Net Realized (Losses) Gains and Other-Than-Temporary Impairments (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investment [Line Items]
Gross realized gains on securities	$ 1	$ 36	$ 14
Gross realized losses on securities	(4)	(18)	(2)
Foreign exchange (losses) gains	(3)	11	(7)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	(3)	0	0
Debt Securities, Available-for-sale, Allowance for Credit Loss, Sell before Recovery	(12)	0	0
Net realized (losses) gains	(22)	31	7
Gain (Loss) on Investments [Member]
Investment [Line Items]
Foreign exchange (losses) gains	$ (4)	$ 14	$ (5)

Investments - Summary of Roll-F

Investments - Summary of Roll-Forward of Ambac's Cumulative Credit Losses on Debt Securities for Which Portion of Other-than-Temporary Impairment was Recognized in Other Comprehensive Income (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 3	$ 0

Investments - Summary of Source

Investments - Summary of Sources of Collateral Received and Various Investment Agreement in which Collateral Pledged (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investment [Line Items]
Fair Value Of Securities Deposited With Governmental Authorities	$ 24	$ 23
Restricted Cash	$ 12	$ 14	$ 5

Investments - Summary of Fair V

Investments - Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities (Detail2) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Investment [Line Items]
Securities fair value	$ 24	$ 23
Investment Portfolio [Member]
Investment [Line Items]
Fair Value of Cash and Securities Pledged to Derivative Counterparties	27	64
Standard & Poor's, B Rating
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		403
Standard & Poor's, B Rating \| Municipal Bonds [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		10
Standard & Poor's, B Rating \| Mortgage-Backed Securities, Other
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		236
Standard & Poor's, B Rating \| Asset-backed Securities [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		$ 157
Standard & Poor's, B- Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	482
Standard & Poor's, B- Rating [Member] \| Municipal Bonds [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	9
Standard & Poor's, B- Rating [Member] \| Mortgage-Backed Securities, Other
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	240
Standard & Poor's, B- Rating [Member] \| Asset-backed Securities [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	$ 232

Investments - Summary of Net In

Investments - Summary of Net Investment Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investment [Line Items]
Trading Securities, Realized Gain (Loss)	$ 18	$ (26)	$ 1
Investment expense	(6)	(6)	(6)
Interest Income, Debt Securities, Available-for-Sale, Operating	93	66	74
Net investment income	140	17	139
Fixed income securities		61	78
Gains (losses) on securities held as of reporting date [Member]
Investment [Line Items]
Other Investments Income	7	(22)	22
Available-for-sale Securities [Member]
Investment [Line Items]
Fixed income securities	76
Short-term Investments [Member]
Investment [Line Items]
Fixed income securities	22	11	0
Financing Receivable [Member]
Investment [Line Items]
Fixed income securities	0	1	0
Other Investments [Member]
Investment [Line Items]
Fixed income securities	40	(26)	66
Debt Securities, Trading
Investment [Line Items]
Fixed income securities	$ 7	$ (23)	$ 0

Investments (Details)

Investments (Details) - USD ($) $ in Millions	12 Months Ended
Investments (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Other Investments	$ 475	$ 568
Investment [Line Items]
Other Investments	475	568
Trading Securities, Realized Gain (Loss)	18	(26)	$ 1
Debt Securities, Trading, Unrealized Gain (Loss)	25	(48)	23
Gains (losses) on securities held as of reporting date [Member]
Investment [Line Items]
Other investments	7	(22)	$ 22
Carrying Amount [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	77	61
Investment [Line Items]
Other Investments	77	61
Hedge Funds, Multi-strategy [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	112	186
Investment [Line Items]
Other Investments	112	186
Illiquid Investments [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	84	84
Investment [Line Items]
Other Investments	84	84
Interest Rate Contract [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	85	80
Investment [Line Items]
Other Investments	85	80
Interest Rate Contract [Member] \| Carrying Amount [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	39	0
Investment [Line Items]
Other Investments	39	0
Equity [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	38	64
Investment [Line Items]
Other Investments	38	64
Equity [Member] \| Carrying Amount [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	38	53
Investment [Line Items]
Other Investments	38	53
Credit Index Product [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	52	63
Investment [Line Items]
Other Investments	52	63
Private Equity Funds, US
Investments, Debt and Equity Securities [Abstract]
Other Investments	70	47
Investment [Line Items]
Other Investments	70	47
Real Estate [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	21	22
Investment [Line Items]
Other Investments	21	22
Convertibles and Bonds with Warrants Attached
Investments, Debt and Equity Securities [Abstract]
Other Investments	0	8
Investment [Line Items]
Other Investments	0	8
Convertibles and Bonds with Warrants Attached \| Carrying Amount [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	0	8
Investment [Line Items]
Other Investments	0	8
Insurance Linked [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	1	1
Investment [Line Items]
Other Investments	1	1
Equity investments in pooled funds [Member]
Investments, Debt and Equity Securities [Abstract]
Other Investments	463	556
Investment [Line Items]
Other Investments	$ 463	$ 556

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Carrying Amount and Fair Value of Ambac's Financial Assets and Liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Financial assets:
Debt Securities, Available-for-sale	$ 1,710	$ 1,395
Other Investments	475	568
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	274	61	$ 23	$ 35
Derivative assets	26	28
Financial liabilities:
Derivative liabilities	$ 35	$ 38
Estimated Future Premium Payments Weighted Average Discounted Rate	3.20%	3%
Interest Rate Swap [Member]
Financial assets:
Derivative assets	$ 25	$ 27
Financial liabilities:
Derivative liabilities	35	38
Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	2,167	1,967
Loans, at fair value	1,663	1,829
Derivative assets	226	239
Financial liabilities:
Derivative liabilities	1,197	1,048
Long-term Debt	$ 2,710	$ 2,788
Estimated Future Premium Payments Weighted Average Discounted Rate	6.30%	6.80%
Variable Interest Entity [Member] \| Interest Rate Swap [Member]
Financial assets:
Derivative assets	$ 190	$ 190
Financial liabilities:
Derivative liabilities	1,197	1,048
Short-term Investments [Member]
Financial assets:
Debt Securities, Available-for-sale	426	507
Asset-backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	303	224
Collateralized Debt Obligations [Member]
Financial assets:
Debt Securities, Available-for-sale	139	137
Residential Mortgage-Backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	250	238
US Government Debt Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	82	65
Debt Security, Government, Non-US [Member]
Financial assets:
Debt Securities, Available-for-sale	100	76
Corporate Debt Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	745	598
Corporate Debt Securities [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	2,072	1,828
Municipal Bonds [Member]
Financial assets:
Debt Securities, Available-for-sale	72	43
Municipal Bonds [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	95	96
Debt Securities, Trading	0	43
Commercial Mortgage Backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	19	0
Warrant [Member]
Financial assets:
Derivative assets	1	1
Carrying Amount [Member]
Financial assets:
Other Investments	77	61
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	28	44
Loans	2	10
Total financial assets	7,022	6,726
Financial liabilities:
Liabilities for net financial guarantees written	292	159
Long-term Debt	983	1,065
Total financial liabilities	5,474	5,418
Carrying Amount [Member] \| Variable Interest Entity [Member]
Financial assets:
Restricted cash	246	17
Loans, at fair value	1,663	1,829
Financial liabilities:
Long-term Debt	2,967	3,107
Carrying Amount [Member] \| Other Debt Obligations [Member]
Financial assets:
Other Investments	475	568
Carrying Amount [Member] \| Short-term Investments [Member]
Financial assets:
Short term investments	426	507
Carrying Amount [Member] \| Corporate Debt Securities [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	2,072	1,828
Carrying Amount [Member] \| Municipal Bonds [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	95	96
Debt Securities, Trading	0	43
Carrying Amount [Member] \| Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities	35	38
Carrying Amount [Member] \| Interest Rate Swap [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	190
Financial liabilities:
Derivative liabilities	1,197	1,048
Carrying Amount [Member] \| Currency Swaps [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	36	49
Carrying Amount [Member] \| Warrant [Member]
Financial assets:
Derivative assets	1	1
Total Fair Value [Member]
Financial assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	28	44
Other Assets [Member] \| Carrying Amount [Member] \| Interest Rate Swap [Member]
Financial assets:
Derivative assets	25	27
Fair Value Measured at Net Asset Value Per Share [Member]
Financial assets:
Other Investments	386	494
Level 1 [Member]
Financial assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	27	43
Total financial assets	979	833
Financial liabilities:
Liabilities for net financial guarantees written	0	0
Long-term Debt	0	0
Total financial liabilities	0	0
Level 1 [Member] \| Variable Interest Entity [Member]
Financial assets:
Restricted cash	246	17
Loans	0	0
Financial liabilities:
Long-term Debt	0	0
Level 1 [Member] \| Other Debt Obligations [Member]
Financial assets:
Other Investments	77	61
Level 1 [Member] \| Short-term Investments [Member]
Financial assets:
Short term investments	421	506
Level 1 [Member] \| Corporate Debt Securities [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Level 1 [Member] \| Municipal Bonds [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Debt Securities, Trading	0	0
Level 1 [Member] \| Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities	0	0
Level 1 [Member] \| Interest Rate Swap [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	0	190
Financial liabilities:
Derivative liabilities	0	0
Level 1 [Member] \| Currency Swaps [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	0	0
Level 1 [Member] \| Loans Receivable [Member]
Financial assets:
Loans	0	0
Level 1 [Member] \| Other Assets [Member] \| Interest Rate Swap [Member]
Financial assets:
Derivative assets	0	0
Level 2 [Member]
Financial assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	2	1
Total financial assets	1,795	1,615
Financial liabilities:
Liabilities for net financial guarantees written	0	0
Long-term Debt	679	864
Total financial liabilities	4,671	4,942
Level 2 [Member] \| Variable Interest Entity [Member]
Financial assets:
Restricted cash		0
Loans	0	0
Financial liabilities:
Long-term Debt	2,760	2,992
Level 2 [Member] \| Variable Interest Entity [Member] \| Interest Rate Swap [Member]
Financial assets:
Derivative assets		190
Level 2 [Member] \| Other Debt Obligations [Member]
Financial assets:
Other Investments	0	0
Level 2 [Member] \| Short-term Investments [Member]
Financial assets:
Short term investments	5	1
Level 2 [Member] \| Corporate Debt Securities [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Level 2 [Member] \| Municipal Bonds [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	95	96
Debt Securities, Trading	0	43
Level 2 [Member] \| Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities	35	38
Level 2 [Member] \| Interest Rate Swap [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	190	0
Financial liabilities:
Derivative liabilities	1,197	1,048
Level 2 [Member] \| Currency Swaps [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	36	49
Level 2 [Member] \| Loans Receivable [Member]
Financial assets:
Loans	0	0
Level 2 [Member] \| Other Assets [Member] \| Interest Rate Swap [Member]
Financial assets:
Derivative assets	0	1
Level 3 [Member]
Financial assets:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	0	0
Total financial assets	3,850	3,772
Financial liabilities:
Liabilities for net financial guarantees written	788	476
Long-term Debt	18	14
Total financial liabilities	1,026	644
Level 3 [Member] \| Variable Interest Entity [Member]
Financial assets:
Restricted cash	0	0
Loans	1,663	1,829
Financial liabilities:
Long-term Debt	220	154
Level 3 [Member] \| Variable Interest Entity [Member] \| Interest Rate Swap [Member]
Financial assets:
Derivative assets	0	0
Level 3 [Member] \| Other Debt Obligations [Member]
Financial assets:
Other Investments	0	0
Level 3 [Member] \| Short-term Investments [Member]
Financial assets:
Short term investments	0	0
Level 3 [Member] \| Corporate Debt Securities [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	2,072	1,828
Level 3 [Member] \| Municipal Bonds [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Debt Securities, Trading	0	0
Level 3 [Member] \| Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities	0	0
Level 3 [Member] \| Interest Rate Swap [Member] \| Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	0	0
Level 3 [Member] \| Currency Swaps [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	0	0
Level 3 [Member] \| Loans Receivable [Member]
Financial assets:
Loans	2	10
Level 3 [Member] \| Warrant [Member]
Financial assets:
Derivative assets	1	1
Level 3 [Member] \| Other Assets [Member] \| Interest Rate Swap [Member]
Financial assets:
Derivative assets	25	26
Municipal Bonds [Member] \| Carrying Amount [Member]
Financial assets:
Debt Securities, Available-for-sale	99	102
Corporate Debt Securities [Member] \| Carrying Amount [Member]
Financial assets:
Debt Securities, Available-for-sale	745	598
Debt Security, Government, Non-US [Member] \| Carrying Amount [Member]
Financial assets:
Debt Securities, Available-for-sale	100	76
US Government Debt Securities [Member] \| Carrying Amount [Member]
Financial assets:
Debt Securities, Available-for-sale	82	65
Residential Mortgage-Backed Securities [Member] \| Carrying Amount [Member]
Financial assets:
Debt Securities, Available-for-sale	250	238
Collateralized Debt Obligations [Member] \| Carrying Amount [Member]
Financial assets:
Debt Securities, Available-for-sale	139	137
Asset-backed Securities [Member] \| Carrying Amount [Member]
Financial assets:
Debt Securities, Available-for-sale	303	224
Commercial Mortgage Backed Securities [Member] \| Carrying Amount [Member]
Financial assets:
Debt Securities, Available-for-sale	19	15
Fair Value, Recurring [Member]
Financial assets:
Total financial assets	7,010	6,715
Financial liabilities:
Liabilities for net financial guarantees written	788	476
Long-term Debt	697	878
Total financial liabilities	5,697	5,586
Fair Value, Recurring [Member] \| Variable Interest Entity [Member]
Financial assets:
Restricted cash	246	17
Loans	1,663	1,829
Financial liabilities:
Long-term Debt	2,980	3,145
Fair Value, Recurring [Member] \| Other Debt Obligations [Member]
Financial assets:
Other Investments	463	556
Fair Value, Recurring [Member] \| Short-term Investments [Member]
Financial assets:
Short term investments	426	507
Fair Value, Recurring [Member] \| Asset-backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	303	224
Fair Value, Recurring [Member] \| Collateralized Debt Obligations [Member]
Financial assets:
Debt Securities, Available-for-sale	139	137
Fair Value, Recurring [Member] \| Residential Mortgage-Backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	250	238
Fair Value, Recurring [Member] \| US Government Debt Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	82	65
Fair Value, Recurring [Member] \| Debt Security, Government, Non-US [Member]
Financial assets:
Debt Securities, Available-for-sale	100	76
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	745	598
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	2,072	1,828
Fair Value, Recurring [Member] \| Municipal Bonds [Member]
Financial assets:
Debt Securities, Available-for-sale	99	102
Fair Value, Recurring [Member] \| Municipal Bonds [Member] \| Variable Interest Entity [Member]
Financial assets:
Debt Securities, Available-for-sale	95	96
Debt Securities, Trading	0	43
Fair Value, Recurring [Member] \| Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities	35	38
Fair Value, Recurring [Member] \| Interest Rate Swap [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	190	190
Financial liabilities:
Derivative liabilities	1,197	1,048
Fair Value, Recurring [Member] \| Currency Swaps [Member] \| Variable Interest Entity [Member]
Financial assets:
Derivative assets	36	49
Fair Value, Recurring [Member] \| Loans Receivable [Member]
Financial assets:
Loans	2	10
Fair Value, Recurring [Member] \| Commercial Mortgage Backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	19
Fair Value, Recurring [Member] \| Other Assets [Member] \| Interest Rate Swap [Member]
Financial assets:
Derivative assets	25	27
Fair Value, Recurring [Member] \| Level 1 [Member] \| Asset-backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 1 [Member] \| Collateralized Debt Obligations [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 1 [Member] \| Residential Mortgage-Backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 1 [Member] \| US Government Debt Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	82	65
Fair Value, Recurring [Member] \| Level 1 [Member] \| Debt Security, Government, Non-US [Member]
Financial assets:
Debt Securities, Available-for-sale	100	76
Fair Value, Recurring [Member] \| Level 1 [Member] \| Corporate Debt Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 1 [Member] \| Municipal Bonds [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 1 [Member] \| Commercial Mortgage Backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 2 [Member] \| Asset-backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	235	157
Fair Value, Recurring [Member] \| Level 2 [Member] \| Collateralized Debt Obligations [Member]
Financial assets:
Debt Securities, Available-for-sale	139	137
Fair Value, Recurring [Member] \| Level 2 [Member] \| Residential Mortgage-Backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	250	238
Fair Value, Recurring [Member] \| Level 2 [Member] \| US Government Debt Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 2 [Member] \| Debt Security, Government, Non-US [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 2 [Member] \| Corporate Debt Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	726	585
Fair Value, Recurring [Member] \| Level 2 [Member] \| Municipal Bonds [Member]
Financial assets:
Debt Securities, Available-for-sale	99	102
Fair Value, Recurring [Member] \| Level 2 [Member] \| Commercial Mortgage Backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	19	15
Fair Value, Recurring [Member] \| Level 3 [Member] \| Asset-backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	68	67
Fair Value, Recurring [Member] \| Level 3 [Member] \| Collateralized Debt Obligations [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 3 [Member] \| Residential Mortgage-Backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 3 [Member] \| US Government Debt Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 3 [Member] \| Debt Security, Government, Non-US [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 3 [Member] \| Corporate Debt Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	19	12
Fair Value, Recurring [Member] \| Level 3 [Member] \| Municipal Bonds [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Level 3 [Member] \| Commercial Mortgage Backed Securities [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Collateral Pledged [Member]
Financial assets:
Debt Securities, Available-for-sale	27	64
Collateral Pledged [Member] \| Short-term Investments [Member]
Financial assets:
Debt Securities, Available-for-sale	27	64
Collateral Pledged [Member] \| Short-term Investments [Member] \| Carrying Amount [Member]
Financial assets:
Debt Securities, Available-for-sale	27	64
Collateral Pledged [Member] \| Fair Value, Recurring [Member] \| Short-term Investments [Member]
Financial assets:
Debt Securities, Available-for-sale	27	64
Collateral Pledged [Member] \| Fair Value, Recurring [Member] \| Level 1 [Member] \| Short-term Investments [Member]
Financial assets:
Debt Securities, Available-for-sale	27	64
Collateral Pledged [Member] \| Fair Value, Recurring [Member] \| Level 2 [Member] \| Short-term Investments [Member]
Financial assets:
Debt Securities, Available-for-sale	0	0
Collateral Pledged [Member] \| Fair Value, Recurring [Member] \| Level 3 [Member] \| Short-term Investments [Member]
Financial assets:
Debt Securities, Available-for-sale	$ 0	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other Investments	$ 475	$ 568
Fair value of derivative liabilities	35
Derivative liabilities	$ 35	$ 38
Weighted average discounted rate of estimated future premium payments to be paid by the VIEs	3.20%	3%
Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Percentage of investment portfolio valued using dealer quotes	2%	5%
Asset-backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Coupon rate	5.97%	5.98%
Minimum [Member] \| Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Percentage of investment portfolio valued using internal valuation models	4%	4%
Maximum [Member] \| Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Percentage of investment portfolio valued using external pricing services	94%	91%
Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value of derivative liabilities	$ 0
Derivative liabilities	$ 1,197	$ 1,048
Weighted average discounted rate of estimated future premium payments to be paid by the VIEs	6.30%	6.80%
Real Estate [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other Investments	$ 21	$ 22
Hedge Funds, Multi-strategy [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other Investments	112	186
Interest Rate Contract [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other Investments	85	80
Illiquid Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other Investments	$ 84	$ 84

Fair Value Measurements - Infor

Fair Value Measurements - Information about Valuation Inputs for Fixed Income Securities Classified as Level 3 (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Investments	$ 475	$ 568
Debt Securities, Available-for-sale	$ 1,710	$ 1,395
Asset-backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Coupon rate	5.97%	5.98%
Fair Value Inputs Maturity	12 years 9 months 18 days	13 years 5 months 15 days
Yield	12%	12.60%
Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Debt Securities, Available-for-sale	$ 2,167	$ 1,967
Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Investments	21	22
Hedge Funds, Multi-strategy [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Investments	112	186
Interest Rate Contract [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Investments	85	80
Illiquid Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other Investments	84	84
Residential Mortgage-Backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Debt Securities, Available-for-sale	250	238
Corporate Obligations [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Debt Securities, Available-for-sale	745	598
Corporate Obligations [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Debt Securities, Available-for-sale	2,072	1,828
Corporate Obligations [Member] \| Variable Interest Entity, Primary Beneficiary [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Debt Securities, Available-for-sale	2,072	1,828
Fair Value, Recurring [Member] \| Residential Mortgage-Backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Debt Securities, Available-for-sale	250	238
Fair Value, Recurring [Member] \| Residential Mortgage-Backed Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Debt Securities, Available-for-sale	0	0
Fair Value, Recurring [Member] \| Corporate Obligations [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Debt Securities, Available-for-sale	745	598
Fair Value, Recurring [Member] \| Corporate Obligations [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Debt Securities, Available-for-sale	$ 19	$ 12
Fair Value Inputs Maturity	10 months 20 days	1 year 9 months
Fair Value, Recurring [Member] \| Corporate Obligations [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Debt Securities, Available-for-sale	$ 2,072	$ 1,828

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Information about Described Model Inputs Used to Determine Fair Value of Each Class of Credit Derivatives (Detail) $ in Millions	Dec. 31, 2023 USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value of derivative liabilities	$ 35

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Information about Described Model Inputs Used to Determine Fair Value of Each Class of Credit Derivatives (Detail2) $ in Millions	Dec. 31, 2023 USD ($)
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value of derivative liabilities	$ 35

Fair Value Measurements - Inf_2

Fair Value Measurements - Information about Valuation Inputs for Variable Interest Entity Assets and Liabilities Classified as Level 3 (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Estimated Future Premium Payments Weighted Average Discounted Rate	3.20%	3%
Asset-backed Securities [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Inputs Coupon Rate	5.97%	5.98%
Fair Value Inputs Maturity	12 years 9 months 18 days	13 years 5 months 15 days
Fair Value Inputs Yield	12%	12.60%
Variable Interest Entity [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			$ 235
Estimated Future Premium Payments Weighted Average Discounted Rate	6.30%	6.80%
Estimated Future Premium Payments Minimum Discounted Rate	5.30%	5.80%
Estimated Future Premium Payments Maximum Discounted Rate	7.80%	8.50%

Fair Value Measurements - Sum_4

Fair Value Measurements - Summary of Changes in Level 3 Fair Value Category (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Financial Assets and Liabilities Transfers In or Out of Level 3	0
Fair Value Yield Rate	11.20%	11.30%
Level 3 [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 3,848	$ 3,762	$ 6,199	$ 6,376
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings	343		230
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)			(58)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	170	(644)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		(1,160)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	6	0	13
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(300)	(633)	(362)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	(343)	1,160	(227)
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	170
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI		(644)	(59)
Level 3 [Member] \| Investments [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	87	79	91	78
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings	1		1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)			1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	3	(12)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	6	0	13
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(2)	(1)	(2)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	(1)	(1)	1
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	3
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI		(12)	(1)
Level 3 [Member] \| Other Assets [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			0	1
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings			0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements			(1)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date			0
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI			0
Level 3 [Member] \| Derivative Financial Instruments, Liabilities [Member] \| Derivative Financial Instruments, Liabilities [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	26	26	70	84
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings	0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			(6)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		(38)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	(6)	(8)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	0	38	6
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI		0	0
Variable Interest Entity, Primary Beneficiary [Member] \| Level 3 [Member] \| Loans Receivable [Member] \| Loans [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	1,663	1,829	2,718	2,998
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings	142		59
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)			(26)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	100	(279)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		(333)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(274)	(278)	(313)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	(142)	333	(59)
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	100
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI		(279)	(26)
Variable Interest Entity, Primary Beneficiary [Member] \| Level 3 [Member] \| Corporate Debt Securities [Member] \| Investments Contract [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	2,072	1,828	3,320	$ 3,215
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings	200		176
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)			(32)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	68	(353)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings		(789)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(24)	(349)	(38)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	(200)	789	(176)
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	$ 68
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI		$ (353)	$ (32)

Fair Value Measurements - Sum_5

Fair Value Measurements - Summary of Gains and Losses (Realized and Unrealized) Relating to Level 3 Assets and Liabilities Included in Earnings (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	$ 0	$ 0	$ 0
Variable Interest Entity [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	341	(1,123)	235
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			235
Net Investment Income [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		1	1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	0	1	1
Derivative Contract [Domain]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	(38)	(6)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	0	(39)	(6)
Income Loss On Variable Interest Entities [Member] \| Variable Interest Entity [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	341	(1,123)
Other Income or (Loss) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	$ 0	$ 0	$ 0

Financial Guarantees in Force -

Financial Guarantees in Force - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Guarantor Obligations [Line Items]
Financial Guarantee Insurance Contracts, Accelerated Premium Revenue, Amount	$ 0	$ 8	$ 1
Gross par amount of financial guarantees outstanding	26,005	27,551
Net par amount of financial guarantees	19,541	22,613
Gross financial guarantees in force	41,733	44,734
Net financial guarantees in force	$ 29,121	34,975
Ceded Principal Outstanding Major Reinsurer Percentage	10.60%
Public Finance [Member]
Guarantor Obligations [Line Items]
Net par amount of financial guarantees	$ 7,562	$ 10,547

Financial Guarantees in Force_3

Financial Guarantees in Force - Summary of Financial Guarantee Portfolio Diversification by Type of Guaranteed Bond (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	$ 19,541	$ 22,613
Total Net Par Outstanding Does Not Exceed This Percentage in Any of the States in the US	6%
Highest single insured risk of aggregate net par amount guaranteed	4.60%
Public Finance [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	$ 7,562	10,547
Public Finance [Member] \| Lease and Tax-backed Revenue [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1,542	1,979
Public Finance [Member] \| General Obligation [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1,051	1,301
Public Finance [Member] \| Housing Revenue [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	3,443	5,491
Public Finance [Member] \| Housing Revenue [Member] \| Military Housing [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	3,371	5,400
Public Finance [Member] \| Other [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1,526	1,776
Structured Finance [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	3,315	3,612
Structured Finance [Member] \| Mortgage-backed and Home Equity [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1,712	1,930
Structured Finance [Member] \| Investor-owned Utilities [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1,077	1,103
Structured Finance [Member] \| Other Structured Finance [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	526	579
International Finance [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	8,664	8,454
International Finance [Member] \| Asset Backed and Other [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	862	1,083
International Finance [Member] \| Investor-owned and Public Utilities [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	2,855	2,583
International Finance [Member] \| Sovereign/Sub-sovereign [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	4,221	4,077
International Finance [Member] \| Transportation [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	$ 726	$ 711

Financial Guarantees in Force_4

Financial Guarantees in Force - Summary of International Finance Guaranteed Portfolio (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	$ 19,541	$ 22,613
International Finance [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	8,664	8,454
International Finance [Member] \| United Kingdom [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	7,502	7,223
International Finance [Member] \| Australia [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	266	259
International Finance [Member] \| Italy [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	576	644
International Finance [Member] \| AUSTRIA
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	307	310
International Finance [Member] \| FRANCE
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	12	14
International Finance [Member] \| Other International [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	1	4
International Finance [Member] \| United States [Member]
Guarantor Obligations [Line Items]
Net Par Amount Outstanding	$ 10,877	$ 14,159

Financial Guarantee Insurance_3

Financial Guarantee Insurance Contracts - Additional Information (Detail) € in Millions, £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2023 GBP (£)	Dec. 31, 2023 EUR (€)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 EUR (€)	Dec. 31, 2021 GBP (£)	Dec. 31, 2021 EUR (€)	Dec. 31, 2020 USD ($)
Insurance [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered		$ 0	$ 0
Estimated Future Premium Payments Weighted Average Discounted Rate	3.20%	3%		3.20%	3.20%	3%	3%
Amount Of Insured Par Outstanding Ceded To Reinsurer	$ 2,766
Ceded Principal Outstanding Major Reinsurer Percentage	10.60%
Reinsurance Payable	$ 90	$ 39
Weighted average period of future premiums	7 years 8 months 12 days	8 years
Uncollectable premium receivables	$ 4	$ 5
Accelerated premium revenue for retired obligations	0	8	1
Reinsurance recoveries of losses included in losses and loss expenses	(110)	(41)	5
Losses and loss expense reserves ceded to reinsurers		33
Subrogation recoveries, net of reinsurance	0	(140)
Amortization of intangible assets	29	47	55
Intangible assets, less accumulated amortization	307	326
Financial Guarantee Outstanding Principal Ceded To Third Parties	6,464
Premiums Receivable, Gross	290	269	323							$ 370
Allowance for Doubtful Accounts, Premiums and Other Receivables	4	5	9							$ 17
Premium Receivable, Credit Loss Expense (Reversal)	(1)	(4)	(6)
Premium Receivable, Allowance for Credit Loss, Writeoff	0	0	(2)
Reinsurance Recoverable, Allowance for Credit Loss	0	0
Net Incurred RMBS Subrogation Recoveries	0	(123)	20
Reinsurance Recoverables, Gross	195
Net unsecured reinsurance recoverable	128
Reinsurance Recoverable, Gross, All Other	50
Unsecured Reinsurance Recoverable, All Other	21
Uncollateralized Credit Exposure Supoorted by Unlimited Uncapped Indemnity	44	45
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	(194)	(1,867)	59
Settled Litigation
Insurance [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years		1,687
Financial Guarantee
Insurance [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered	8
Losses and loss expense reserves ceded to reinsurers	30
Financial Guarantee \| Assured Guaranty Re Ltd [Member]
Insurance [Line Items]
Reinsurance Recoverables, Gross	25
Net unsecured reinsurance recoverable	0
Property and Casualty, Commercial Insurance \| QBE Insurance Corporation
Insurance [Line Items]
Reinsurance Recoverables, Gross	38
Net unsecured reinsurance recoverable	38
Property and Casualty, Commercial Insurance \| General Reinsurance Company
Insurance [Line Items]
Reinsurance Recoverables, Gross	81
Net unsecured reinsurance recoverable	69
Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	210	217
IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	16	10
II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	5	5
III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	7	16
IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	$ 11	$ 11
Maximum [Member] \| Furniture and Fixtures [Member]
Insurance [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years			5 years	5 years
Loss Reserves [Member]
Insurance [Line Items]
Weighted average risk-free rate used to discount loss reserves	3.90%	3.90%
United Kingdom, Pounds
Insurance [Line Items]
Financial Guarantee Insurance Contracts, Premium Receivable	$ 72	$ 71	108	£ 57		£ 59		£ 80
Euro Member Countries, Euro
Insurance [Line Items]
Financial Guarantee Insurance Contracts, Premium Receivable	13	14	$ 16		€ 12		€ 13		€ 14
Public Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	140	150
Public Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	133	142
Public Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	3	3
Public Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	5	5
Public Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Public Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Structured Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	22	24
Structured Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	4	5
Structured Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	1
Structured Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Structured Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	7	7
Structured Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	11	11
International Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	85	85
International Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	72	70
International Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	13	7
International Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
International Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	9
International Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Housing Revenue [Member] \| Public Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	139	148
Housing Revenue [Member] \| Public Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	131	140
Housing Revenue [Member] \| Public Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	3	3
Housing Revenue [Member] \| Public Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	5	5
Housing Revenue [Member] \| Public Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Housing Revenue [Member] \| Public Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Public Finance Sectors [Member] \| Public Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	1	2
Other Public Finance Sectors [Member] \| Public Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	1	2
Other Public Finance Sectors [Member] \| Public Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Public Finance Sectors [Member] \| Public Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Public Finance Sectors [Member] \| Public Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Public Finance Sectors [Member] \| Public Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Student Loan [Member] \| Structured Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	7	8
Student Loan [Member] \| Structured Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	1
Student Loan [Member] \| Structured Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	1
Student Loan [Member] \| Structured Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Student Loan [Member] \| Structured Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	7	7
Student Loan [Member] \| Structured Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Structured Finance [Member] \| Structured Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	4	4
Other Structured Finance [Member] \| Structured Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	4	4
Other Structured Finance [Member] \| Structured Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Structured Finance [Member] \| Structured Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Structured Finance [Member] \| Structured Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other Structured Finance [Member] \| Structured Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Sovereign/Sub-sovereign [Member] \| International Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	64	64
Sovereign/Sub-sovereign [Member] \| International Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	51	49
Sovereign/Sub-sovereign [Member] \| International Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	13	7
Sovereign/Sub-sovereign [Member] \| International Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Sovereign/Sub-sovereign [Member] \| International Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	9
Sovereign/Sub-sovereign [Member] \| International Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Investor-owned and Public Utilities [Member] \| International Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	18	18
Investor-owned and Public Utilities [Member] \| International Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	18	18
Investor-owned and Public Utilities [Member] \| International Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Investor-owned and Public Utilities [Member] \| International Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Investor-owned and Public Utilities [Member] \| International Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Investor-owned and Public Utilities [Member] \| International Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other International [Member] \| International Finance [Member]
Insurance [Line Items]
Premiums Receivable, Gross	3	2
Other International [Member] \| International Finance [Member] \| Surveillance Category One [Member]
Insurance [Line Items]
Premiums Receivable, Gross	3	2
Other International [Member] \| International Finance [Member] \| IA [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other International [Member] \| International Finance [Member] \| II [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other International [Member] \| International Finance [Member] \| III [Member]
Insurance [Line Items]
Premiums Receivable, Gross	0	0
Other International [Member] \| International Finance [Member] \| IV [Member]
Insurance [Line Items]
Premiums Receivable, Gross	$ 0	$ 0

Financial Guarantee Insurance_4

Financial Guarantee Insurance Contracts - Summary of Gross Premium Receivable Roll-Forward (Direct and Assumed Contracts) (Detail) € in Millions, £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2023 GBP (£)	Dec. 31, 2023 EUR (€)	Dec. 31, 2022 USD ($)	Dec. 31, 2022 GBP (£)	Dec. 31, 2022 EUR (€)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Insurance [Line Items]
Premium Receivable, Allowance for Credit Loss	$ 4			$ 5
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,415			1,305			$ 1,098	$ 1,140
Premiums Written, Net	210			117			10
Proceeds from Insurance Premiums Collected	(208)			(139)			(43)
Adjustments for changes in expected and contractual cash flows	6			(31)			(27)
Accretion of premium receivable discount	8			8			8
Financial Guarantee Insurance Contracts, Consolidation of VIE	(1)
Other adjustments (including foreign exchange)	4			(12)			(4)
Allowance for Doubtful Accounts, Premiums and Other Receivables	4			5			9	17
Premium Receivable, Credit Loss Expense (Reversal)	(1)			(4)			(6)
Premium Receivable, Allowance for Credit Loss, Writeoff	0			0			(2)
Premiums Receivable, Gross	290			269			323	$ 370
Premium Receivable, Allowance for Credit Loss, Recovery	0			0			0
Past Due Premiums	1			0
Premium Receivable, Allowance for Credit Loss, Period Increase (Decrease)	1			4			8
Foreign Exchange \| Real Estate [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Other adjustments (including foreign exchange)	4			(13)			(2)
Specialty Property & Casualty Program [Domain]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	46			16
Legacy Financial Guarantee
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	248			259
Surveillance Category One [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	210			217
IA [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	16			10
II [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	5			5
III [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	7			16
IV [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	11			11
United Kingdom, Pounds
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Beginning premium receivable	71	£ 59		108	£ 80
Ending premium receivable	72	£ 57		71	£ 59		108
Euro Member Countries, Euro
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Beginning premium receivable	14		€ 13	16		€ 14
Ending premium receivable	13		€ 12	14		€ 13	$ 16
Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	22			24
Structured Finance [Member] \| Mortgage-backed and Home Equity [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	12			11
Structured Finance [Member] \| Student Loan [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	7			8
Structured Finance [Member] \| Other Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	4			4
Structured Finance [Member] \| Surveillance Category One [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	4			5
Structured Finance [Member] \| Surveillance Category One [Member] \| Mortgage-backed and Home Equity [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Structured Finance [Member] \| Surveillance Category One [Member] \| Student Loan [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			1
Structured Finance [Member] \| Surveillance Category One [Member] \| Other Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	4			4
Structured Finance [Member] \| IA [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			1
Structured Finance [Member] \| IA [Member] \| Mortgage-backed and Home Equity [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Structured Finance [Member] \| IA [Member] \| Student Loan [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			1
Structured Finance [Member] \| IA [Member] \| Other Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Structured Finance [Member] \| II [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Structured Finance [Member] \| II [Member] \| Mortgage-backed and Home Equity [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Structured Finance [Member] \| II [Member] \| Student Loan [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Structured Finance [Member] \| II [Member] \| Other Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Structured Finance [Member] \| III [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	7			7
Structured Finance [Member] \| III [Member] \| Mortgage-backed and Home Equity [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Structured Finance [Member] \| III [Member] \| Student Loan [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	7			7
Structured Finance [Member] \| III [Member] \| Other Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Structured Finance [Member] \| IV [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	11			11
Structured Finance [Member] \| IV [Member] \| Mortgage-backed and Home Equity [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	11			11
Structured Finance [Member] \| IV [Member] \| Student Loan [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Structured Finance [Member] \| IV [Member] \| Other Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	140			150
Public Finance [Member] \| Housing Revenue [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	139			148
Public Finance [Member] \| Other Public Finance Sectors [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	1			2
Public Finance [Member] \| Surveillance Category One [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	133			142
Public Finance [Member] \| Surveillance Category One [Member] \| Housing Revenue [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	131			140
Public Finance [Member] \| Surveillance Category One [Member] \| Other Public Finance Sectors [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	1			2
Public Finance [Member] \| IA [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3			3
Public Finance [Member] \| IA [Member] \| Housing Revenue [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3			3
Public Finance [Member] \| IA [Member] \| Other Public Finance Sectors [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Public Finance [Member] \| II [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	5			5
Public Finance [Member] \| II [Member] \| Housing Revenue [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	5			5
Public Finance [Member] \| II [Member] \| Other Public Finance Sectors [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Public Finance [Member] \| III [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Public Finance [Member] \| III [Member] \| Housing Revenue [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Public Finance [Member] \| III [Member] \| Other Public Finance Sectors [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Public Finance [Member] \| IV [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Public Finance [Member] \| IV [Member] \| Housing Revenue [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
Public Finance [Member] \| IV [Member] \| Other Public Finance Sectors [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	85			85
International Finance [Member] \| Sovereign/Sub-sovereign [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	64			64
International Finance [Member] \| Investor-owned and Public Utilities [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	18			18
International Finance [Member] \| Other International [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3			2
International Finance [Member] \| Surveillance Category One [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	72			70
International Finance [Member] \| Surveillance Category One [Member] \| Sovereign/Sub-sovereign [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	51			49
International Finance [Member] \| Surveillance Category One [Member] \| Investor-owned and Public Utilities [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	18			18
International Finance [Member] \| Surveillance Category One [Member] \| Other International [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3			2
International Finance [Member] \| IA [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	13			7
International Finance [Member] \| IA [Member] \| Sovereign/Sub-sovereign [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	13			7
International Finance [Member] \| IA [Member] \| Investor-owned and Public Utilities [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member] \| IA [Member] \| Other International [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member] \| II [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member] \| II [Member] \| Sovereign/Sub-sovereign [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member] \| II [Member] \| Investor-owned and Public Utilities [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member] \| II [Member] \| Other International [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member] \| III [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			9
International Finance [Member] \| III [Member] \| Sovereign/Sub-sovereign [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			9
International Finance [Member] \| III [Member] \| Investor-owned and Public Utilities [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member] \| III [Member] \| Other International [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member] \| IV [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member] \| IV [Member] \| Sovereign/Sub-sovereign [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member] \| IV [Member] \| Investor-owned and Public Utilities [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0			0
International Finance [Member] \| IV [Member] \| Other International [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	$ 0			$ 0

Financial Guarantee Insurance_5

Financial Guarantee Insurance Contracts - Effect of Reinsurance on Premiums Written and Earned (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums Written	$ (249)	$ (127)	$ (2)
Assumed Reinsurance Premiums Written	40	0	0
Ceded Reinsurance Premiums Written	(244)	(104)	(35)
Premiums written, net of reinsurance	(44)	(23)	33
Direct Premiums Earned	224	126	62
Premiums Earned, Net	78	56	47
Assumed Reinsurance Premiums Earned	18	0	0
Ceded Reinsurance Premiums Earned	164	69	15
Reinsurance on premiums earned, Net	78	56	$ 47
Reinsurance Recoverable, Allowance for Credit Loss	$ 0	$ 0

Financial Guarantee Insurance_6

Financial Guarantee Insurance Contracts - Summarized Future Gross Undiscounted Premiums Expected to be Collected, and Future Expected Premiums Earned, Net of Reinsurance (Detail) $ in Millions	Dec. 31, 2023 USD ($)
Future premiums expected to be collected, March 31, 2022	$ 8
Future premiums expected to be collected, June 30. 2022	6
Future premiums expected to be collected, September 30, 2022	7
Future premiums expected to be collected, December 31, 2022	5
Future premiums expected to be collected, December 31, 2023	26
Future premiums expected to be collected, December 31, 2024	25
Future premiums expected to be collected, December 31, 2025	24
Future premiums expected to be collected, December 31, 2026	23
Future premiums expected to be collected, December 31, 2031	93
Future premiums expected to be collected, December 31, 2036	54
Future premiums expected to be collected, December 31, 2041	25
Future premiums expected to be collected, December 31, 2046	12
Future premiums expected to be collected, December 31, 2051	2
Future premiums expected to be collected, Total	310
Future expected premium to be earned, net of reinsurance, March 31, 2022	5
Future expected premiums to be earned, net of reinsurance, June 30, 2022	4
Future expected premiums to be earned, net of reinsurance, September 30, 2022	4
Future expected premiums to be earned, net of reinsurance, December 31, 2022	4
Future expected premiums to be earned, net of reinsurance, December 31, 2023	16
Future expected premiums to be earned, net of reinsurance, December 31, 2024	16
Future expected premiums to be earned, net of reinsurance, December 31, 2025	15
Future expected premiums to be earned, net of reinsurance, December 31, 2026	14
Future expected premiums to be earned, net of reinsurance, December 31, 2031	55
Future expected premiums to be earned, net of reinsurance, December 31, 2036	28
Future expected premiums to be earned, net of reinsurance, December 31, 2041	9
Future expected premiums to be earned, net of reinsurance, December 31, 2046	4
Future expected premiums to be earned, net of reinsurance, December 31, 2051	1
Future expected premiums to be earned, net of reinsurance, Total	$ 173

Financial Guarantee Insurance_7

Financial Guarantee Insurance Contracts Financial Guarantee Insurance Contracts - Components of Loss and Loss Expense Reserves and Subrogation Recoverable (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Policyholder Benefits and Claims Incurred, Ceded	$ 110	$ 41	$ (5)
Liability for Unpaid Claims and Claims Adjustment Expense, Net	577	883	(578)	$ (430)
Subrogation recoverable	(137)	(271)
Claim liability reported on Balance Sheet, before reinsurance		444
Liability for Claims and Claims Adjustment Expense	893	805
Liabillity for Claim and Claim Adjustment Expense, with Impact of VIE Consolidation	756	534	(522)	$ (397)
Premiums Earned, Net	78	56	47
Legacy Financial Guarantee
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Liability for Claims and Claims Adjustment Expense	696	715	1,538
Premiums Earned, Net	26	42	$ 46
Property and Casualty, Commercial Insurance
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Liability for Claims and Claims Adjustment Expense	197	90
Liabillity for Claim and Claim Adjustment Expense, with Impact of VIE Consolidation	197	90
Unearned Premium Reserve [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Subrogation recoverable	0	0
Claim liability reported on Balance Sheet, before reinsurance	(28)	(28)
Liability for Claims and Claims Adjustment Expense	(28)	(28)
Present Value of Expected Net Cash Flows- Claims and Loss Expenses [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Subrogation recoverable	1	5
Claim liability reported on Balance Sheet, before reinsurance	780	791
Liability for Claims and Claims Adjustment Expense	779	787
Present Value of Expected Net Cash Flows-Recoveries [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Subrogation recoverable	(139)	(276)
Claim liability reported on Balance Sheet, before reinsurance	(194)	(319)
Liability for Claims and Claims Adjustment Expense	$ (55)	$ (44)

Financial Guarantee Insurance_8

Financial Guarantee Insurance Contracts - Summary of Loss Reserve Roll-Forward, Net of Subrogation Recoverable and Reinsurance (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Loss And Loss Adjustment Expense Reserves [Line Items]
Impact of VIE Consolidation on Gross Loss and Loss Reserves	$ 7	$ 464
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	0	(2)	$ 0
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	(32)	(397)	(88)
Schedule Of Insured Financial Obligations With Credit Deterioration Reductions Of Gross Claim Liability Rmbs Subrogation	0	(140)
Policyholder Benefits and Claims Incurred, Ceded	110	41	(5)
Net Incurred RMBS Subrogation Recoveries	0	123	(20)
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Less reinsurance on loss and loss expense reserves	33
Beginning balance of net loss and loss expense reserves	883	(578)	(430)
Current year:
Claim and loss expense payments, net of subrogation and reinsurance	(4)	(7)	0
Prior years:
Claim and loss expense (payments) recoveries, net of subrogation and reinsurance	194	1,867	(59)
Liability for Unpaid Claims and Claims Adjustment Expense, Net	577	883	(578)	$ (430)
Add reinsurance on loss and loss expense reserves		33
Liabillity for Claim and Claim Adjustment Expense, with Impact of VIE Consolidation	756	534	(522)	(397)
Balance Of Rmbs Subrogation Recoveries Net Of Reinsurance	0	(140)
Current Year Claims and Claims Adjustment Expense	37	4	0
Prior Year Claims and Claims Adjustment Expense	(69)	(401)	(89)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	(190)	(1,860)	59
Ceded Loss And Loss Expenses Paid Not Yet Recovered		0	0
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	$ 186	115	$ 56	$ 33
Liability For Unpaid Claims And Claims Adjustment Expense Net of VIE Consolidation		$ 419

Financial Guarantee Insurance_9

Financial Guarantee Insurance Contracts - Summary of Information Related to Policies Currently Included in Ambac's Loss Reserves or Subrogation Recoverable (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) Policies	Dec. 31, 2022 USD ($) Policies	Dec. 31, 2021 USD ($)
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies \| Policies	141	162
Remaining weighted-average contract period (in years)	12 years	14 years
Gross insured contractual payments outstanding:
Principal	$ 3,838	$ 4,047
Interest	1,421	1,750
Total	5,259	5,797
Gross undiscounted claim liability	1,202	1,279
Discount, gross claim liability	426	496
Gross claim liability before all subrogation and before reinsurance	777	783
Less:
Gross RMBS subrogation	0	(140)
Discount, RMBS subrogation	0	0
Schedule Of Insured Financial Obligations With Credit Deterioration Reductions Of Gross Claim Liability Rmbs Subrogation	0	(140)
Less:
Gross other subrogation	(263)	(233)
Discount, other subrogation	69	54
Discounted other subrogation, before reinsurance	(194)	(179)
Gross claim liability, net of all subrogation and discounts, before reinsurance	583	464
Less: Unearned premium reserves	(28)	(28)
Plus: Loss adjustment expenses reserves	4	8
Claim liability reported on Balance Sheet, before reinsurance		444
Reinsurance recoverable reported on Balance Sheet	30	33
Ceded Loss And Loss Expenses Paid Not Yet Recovered		0	$ 0
Loss Reserves Ceded To Reinsurers		$ 33
Financial Guarantee
Less:
Claim liability reported on Balance Sheet, before reinsurance	559
Ceded Loss And Loss Expenses Paid Not Yet Recovered	8
Loss Reserves Ceded To Reinsurers	$ 30
Loss Reserves [Member]
Less:
Weighted average risk-free rate used to discount loss reserves	3.90%	3.90%
Surveillance Category One [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies \| Policies	18	37
Remaining weighted-average contract period (in years)	9 years	7 years
Gross insured contractual payments outstanding:
Principal	$ 429	$ 709
Interest	75	526
Total	505	1,235
Gross undiscounted claim liability	1	4
Discount, gross claim liability	0	1
Gross claim liability before all subrogation and before reinsurance	1	3
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Schedule Of Insured Financial Obligations With Credit Deterioration Reductions Of Gross Claim Liability Rmbs Subrogation	0	0
Less:
Gross other subrogation	(13)	(14)
Discount, other subrogation	2	2
Discounted other subrogation, before reinsurance	(11)	(12)
Gross claim liability, net of all subrogation and discounts, before reinsurance	(10)	(9)
Less: Unearned premium reserves	0	(2)
Plus: Loss adjustment expenses reserves	0	1
Claim liability reported on Balance Sheet, before reinsurance	(10)	(10)
Reinsurance recoverable reported on Balance Sheet	$ 1	$ 1
IA [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies \| Policies	8	6
Remaining weighted-average contract period (in years)	9 years	19 years
Gross insured contractual payments outstanding:
Principal	$ 1,084	$ 200
Interest	328	198
Total	1,412	399
Gross undiscounted claim liability	19	4
Discount, gross claim liability	2	1
Gross claim liability before all subrogation and before reinsurance	17	3
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Schedule Of Insured Financial Obligations With Credit Deterioration Reductions Of Gross Claim Liability Rmbs Subrogation	0	0
Less:
Gross other subrogation	(2)	(4)
Discount, other subrogation	0	0
Discounted other subrogation, before reinsurance	(2)	(3)
Gross claim liability, net of all subrogation and discounts, before reinsurance	15	0
Less: Unearned premium reserves	(12)	(2)
Plus: Loss adjustment expenses reserves	3	1
Claim liability reported on Balance Sheet, before reinsurance	6	(2)
Reinsurance recoverable reported on Balance Sheet	$ 0	$ 0
II [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies \| Policies	9	9
Remaining weighted-average contract period (in years)	13 years	14 years
Gross insured contractual payments outstanding:
Principal	$ 430	$ 459
Interest	262	286
Total	692	745
Gross undiscounted claim liability	41	43
Discount, gross claim liability	7	7
Gross claim liability before all subrogation and before reinsurance	34	36
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Schedule Of Insured Financial Obligations With Credit Deterioration Reductions Of Gross Claim Liability Rmbs Subrogation	0	0
Less:
Gross other subrogation	0	0
Discount, other subrogation	0	0
Discounted other subrogation, before reinsurance	0	0
Gross claim liability, net of all subrogation and discounts, before reinsurance	34	36
Less: Unearned premium reserves	(4)	(5)
Plus: Loss adjustment expenses reserves	0	0
Claim liability reported on Balance Sheet, before reinsurance	30	32
Reinsurance recoverable reported on Balance Sheet	$ 8	$ 8
III [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies \| Policies	13	12
Remaining weighted-average contract period (in years)	13 years	14 years
Gross insured contractual payments outstanding:
Principal	$ 394	$ 1,000
Interest	139	156
Total	534	1,156
Gross undiscounted claim liability	324	446
Discount, gross claim liability	86	162
Gross claim liability before all subrogation and before reinsurance	239	284
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Schedule Of Insured Financial Obligations With Credit Deterioration Reductions Of Gross Claim Liability Rmbs Subrogation	0	0
Less:
Gross other subrogation	(27)	(31)
Discount, other subrogation	4	5
Discounted other subrogation, before reinsurance	(23)	(26)
Gross claim liability, net of all subrogation and discounts, before reinsurance	215	258
Less: Unearned premium reserves	0	(8)
Plus: Loss adjustment expenses reserves	0	2
Claim liability reported on Balance Sheet, before reinsurance	215	252
Reinsurance recoverable reported on Balance Sheet	$ 18	$ 21
IV [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies \| Policies	88	93
Remaining weighted-average contract period (in years)	12 years	12 years
Gross insured contractual payments outstanding:
Principal	$ 1,473	$ 1,646
Interest	600	565
Total	2,073	2,210
Gross undiscounted claim liability	772	729
Discount, gross claim liability	323	316
Gross claim liability before all subrogation and before reinsurance	450	413
Less:
Gross RMBS subrogation	0	(140)
Discount, RMBS subrogation	0	0
Schedule Of Insured Financial Obligations With Credit Deterioration Reductions Of Gross Claim Liability Rmbs Subrogation	0	(140)
Less:
Gross other subrogation	(208)	(172)
Discount, other subrogation	60	42
Discounted other subrogation, before reinsurance	(149)	(130)
Gross claim liability, net of all subrogation and discounts, before reinsurance	301	143
Less: Unearned premium reserves	(10)	(10)
Plus: Loss adjustment expenses reserves	1	4
Claim liability reported on Balance Sheet, before reinsurance	292	137
Reinsurance recoverable reported on Balance Sheet	$ 3	$ 3
V [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies \| Policies	5	5
Remaining weighted-average contract period (in years)	7 years	7 years
Gross insured contractual payments outstanding:
Principal	$ 27	$ 34
Interest	17	19
Total	44	53
Gross undiscounted claim liability	44	53
Discount, gross claim liability	8	9
Gross claim liability before all subrogation and before reinsurance	36	43
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Schedule Of Insured Financial Obligations With Credit Deterioration Reductions Of Gross Claim Liability Rmbs Subrogation	0	0
Less:
Gross other subrogation	(11)	(12)
Discount, other subrogation	3	4
Discounted other subrogation, before reinsurance	(8)	(8)
Gross claim liability, net of all subrogation and discounts, before reinsurance	28	35
Less: Unearned premium reserves	(1)	(1)
Plus: Loss adjustment expenses reserves	0	0
Claim liability reported on Balance Sheet, before reinsurance	27	34
Reinsurance recoverable reported on Balance Sheet	$ 0	$ 0

Financial Guarantee Insuranc_10

Financial Guarantee Insurance Contracts - Summary of Balance of RMBS Subrogation Recoveries and Related Claim Liabilities, by Estimation Approach (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Schedule Of Balance Of Rmbs Subrogation Recoveries And Related Claim Liabilities By Estimation Approach [Line Items]
Subrogation recoveries	$ 0	$ 140

Financial Guarantee Insuranc_11

Financial Guarantee Insurance Contracts - Summary of Rollforward of RMBS Subrogation, by Estimation Approach (Detail) $ in Millions	Dec. 31, 2023 USD ($)
Subrogation By Estimation Approach [Roll Forward]
Discounted RMBS subrogation (gross of reinsurance), beginning balance	$ 140
Changes recognized
Discounted RMBS subrogation (gross of reinsurance), ending balance	$ 0

Financial Guarantee Insuranc_12

Financial Guarantee Insurance Contracts - Estimated Future Amortization Expense for Insurance Intangible Asset (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Amortization Of Intangible Assets [Line Items]
Amortization of intangible assets	$ 29	$ 47	$ 55
2018	30
2019	28
2020	26
2021	24
2022	22
Thereafter	162
Intangible assets, less accumulated amortization	$ 307	326
Insurance Intangible Asset [Member]
Amortization Of Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years 1 month 6 days
Amortization of intangible assets	$ 25	44	$ 52
Intangible Assets, Gross (Excluding Goodwill)	1,258	1,247
2018	26
2019	24
2020	22
2021	20
2022	18
Thereafter	136
Finite-Lived Intangible Assets, Accumulated Amortization	1,013	981
Intangible assets, less accumulated amortization	$ 245	$ 266

Financial Guarantee Insurance -

Financial Guarantee Insurance - Summary of Percentage Ceded to Reinsurers and Reinsurance Recoverable and Rating Levels (Detail)	Dec. 31, 2023
Summary of Ceded Par and Net Unsecured Reinsurance Recoverable [Line Items]
Percentage of Ceded Reinsurance Recoverable Represented by Top Three	74%

Financial Guarantee Insuranc_13

Financial Guarantee Insurance Contracts Financial Guarantee Insurance Contracts Earned Premiums by Geographic Location (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Premiums Earned, Net, Financial Guarantee Insurance Contracts	$ 78	$ 56	$ 47
Premiums Receivable, Gross	290	269	323	$ 370
Liability for Claims and Claims Adjustment Expense	893	805
Subrogation recoverable	137	271
Property and Casualty, Commercial Insurance
Liability for Claims and Claims Adjustment Expense	197	90
Public Finance [Member]
Premiums Receivable, Gross	140	150
Structured Finance [Member]
Premiums Receivable, Gross	22	24
International Finance [Member]
Premiums Receivable, Gross	85	85
Housing Revenue [Member] \| Public Finance [Member]
Premiums Receivable, Gross	139	148
Other Public Finance Sectors [Member] \| Public Finance [Member]
Premiums Receivable, Gross	1	2
Mortgage-backed and Home Equity [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	12	11
Student Loan [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	7	8
Other Structured Finance [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	4	4
Sovereign/Sub-sovereign [Member] \| International Finance [Member]
Premiums Receivable, Gross	64	64
Investor-owned and Public Utilities [Member] \| International Finance [Member]
Premiums Receivable, Gross	18	18
Other International [Member] \| International Finance [Member]
Premiums Receivable, Gross	3	2
Surveillance Category One [Member]
Premiums Receivable, Gross	210	217
Surveillance Category One [Member] \| Public Finance [Member]
Premiums Receivable, Gross	133	142
Surveillance Category One [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	4	5
Surveillance Category One [Member] \| International Finance [Member]
Premiums Receivable, Gross	72	70
Surveillance Category One [Member] \| Housing Revenue [Member] \| Public Finance [Member]
Premiums Receivable, Gross	131	140
Surveillance Category One [Member] \| Other Public Finance Sectors [Member] \| Public Finance [Member]
Premiums Receivable, Gross	1	2
Surveillance Category One [Member] \| Mortgage-backed and Home Equity [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	0
Surveillance Category One [Member] \| Student Loan [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	1
Surveillance Category One [Member] \| Other Structured Finance [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	4	4
Surveillance Category One [Member] \| Sovereign/Sub-sovereign [Member] \| International Finance [Member]
Premiums Receivable, Gross	51	49
Surveillance Category One [Member] \| Investor-owned and Public Utilities [Member] \| International Finance [Member]
Premiums Receivable, Gross	18	18
Surveillance Category One [Member] \| Other International [Member] \| International Finance [Member]
Premiums Receivable, Gross	3	2
IA [Member]
Premiums Receivable, Gross	16	10
IA [Member] \| Public Finance [Member]
Premiums Receivable, Gross	3	3
IA [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	1
IA [Member] \| International Finance [Member]
Premiums Receivable, Gross	13	7
IA [Member] \| Housing Revenue [Member] \| Public Finance [Member]
Premiums Receivable, Gross	3	3
IA [Member] \| Other Public Finance Sectors [Member] \| Public Finance [Member]
Premiums Receivable, Gross	0	0
IA [Member] \| Mortgage-backed and Home Equity [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	0
IA [Member] \| Student Loan [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	1
IA [Member] \| Other Structured Finance [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	0
IA [Member] \| Sovereign/Sub-sovereign [Member] \| International Finance [Member]
Premiums Receivable, Gross	13	7
IA [Member] \| Investor-owned and Public Utilities [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
IA [Member] \| Other International [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
II [Member]
Premiums Receivable, Gross	5	5
II [Member] \| Public Finance [Member]
Premiums Receivable, Gross	5	5
II [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	0
II [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
II [Member] \| Housing Revenue [Member] \| Public Finance [Member]
Premiums Receivable, Gross	5	5
II [Member] \| Other Public Finance Sectors [Member] \| Public Finance [Member]
Premiums Receivable, Gross	0	0
II [Member] \| Mortgage-backed and Home Equity [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	0
II [Member] \| Student Loan [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	0
II [Member] \| Other Structured Finance [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	0
II [Member] \| Sovereign/Sub-sovereign [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
II [Member] \| Investor-owned and Public Utilities [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
II [Member] \| Other International [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
III [Member]
Premiums Receivable, Gross	7	16
III [Member] \| Public Finance [Member]
Premiums Receivable, Gross	0	0
III [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	7	7
III [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	9
III [Member] \| Housing Revenue [Member] \| Public Finance [Member]
Premiums Receivable, Gross	0	0
III [Member] \| Other Public Finance Sectors [Member] \| Public Finance [Member]
Premiums Receivable, Gross	0	0
III [Member] \| Mortgage-backed and Home Equity [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	0
III [Member] \| Student Loan [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	7	7
III [Member] \| Other Structured Finance [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	0
III [Member] \| Sovereign/Sub-sovereign [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	9
III [Member] \| Investor-owned and Public Utilities [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
III [Member] \| Other International [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
IV [Member]
Premiums Receivable, Gross	11	11
IV [Member] \| Public Finance [Member]
Premiums Receivable, Gross	0	0
IV [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	11	11
IV [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
IV [Member] \| Housing Revenue [Member] \| Public Finance [Member]
Premiums Receivable, Gross	0	0
IV [Member] \| Other Public Finance Sectors [Member] \| Public Finance [Member]
Premiums Receivable, Gross	0	0
IV [Member] \| Mortgage-backed and Home Equity [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	11	11
IV [Member] \| Student Loan [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	0
IV [Member] \| Other Structured Finance [Member] \| Structured Finance [Member]
Premiums Receivable, Gross	0	0
IV [Member] \| Sovereign/Sub-sovereign [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
IV [Member] \| Investor-owned and Public Utilities [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
IV [Member] \| Other International [Member] \| International Finance [Member]
Premiums Receivable, Gross	0	0
Reportable Geographical Components [Member] \| UNITED STATES
Premiums Earned, Net, Financial Guarantee Insurance Contracts	65	41	27
Reportable Geographical Components [Member] \| UNITED KINGDOM
Premiums Earned, Net, Financial Guarantee Insurance Contracts	11	13	14
Reportable Geographical Components [Member] \| Other International [Member]
Premiums Earned, Net, Financial Guarantee Insurance Contracts	$ 2	$ 3	$ 6

Reinsurance (Details)

Reinsurance (Details) $ in Millions	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Insurance [Line Items]
Letters of Credit Outstanding, Amount	$ 131
Deferred Ceded Premiums And Reinsurance Recoverables	398
Reinsurance Payable	$ 90	$ 39
Percentage of Ceded Reinsurance Recoverable Represented by Top Three	74%
Reinsurance Recoverables, Gross	$ 195
Net unsecured reinsurance recoverable	128
Reinsurance Recoverable, Gross, All Other	50
Unsecured Reinsurance Recoverable, All Other	21
Reinsurance Recoverable Credit Exposure	128	60
Uncollateralized Credit Exposure Supoorted by Unlimited Uncapped Indemnity	$ 44	$ 45
Number of Reinsurers Covering Majority	3
QBE Insurance Corporation \| Property and Casualty, Commercial Insurance
Insurance [Line Items]
Reinsurance Recoverables, Gross	$ 38
Net unsecured reinsurance recoverable	38
Assured Guaranty Re Ltd [Member] \| Financial Guarantee
Insurance [Line Items]
Reinsurance Recoverables, Gross	25
Net unsecured reinsurance recoverable	0
General Reinsurance Company \| Property and Casualty, Commercial Insurance
Insurance [Line Items]
Reinsurance Recoverables, Gross	81
Net unsecured reinsurance recoverable	$ 69

Insurance Contracts (Details)

Insurance Contracts (Details) - USD ($) $ in Millions	12 Months Ended
Insurance Contracts (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Insurance [Line Items]
Other adjustments (including foreign exchange)	$ 4	$ (12)	$ (4)

Insurance Contracts (Details)_2

Insurance Contracts (Details) $ in Millions	12 Months Ended
Insurance Contracts (Details) $ in Millions	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Insurance [Line Items]
Short-Duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	$ 41
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	186	$ 115	$ 56	$ 33
Liability for Claims and Claims Adjustment Expense	893	805
Short Duration Insurance Contract Liability For Unpaid Clams and Allocated Claim Adjustment Expense Subtotal For Separately Presented	22	0
Other adjustments (including foreign exchange)	4	(12)	(4)
Commercial Auto \| Operating Segments
Insurance [Line Items]
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	85
Liability for Claims and Claims Adjustment Expense	107
Unallocated Loss Adjustment Expense Reserve \| Segment Reconciling Items
Insurance [Line Items]
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	2
Liability for Claims and Claims Adjustment Expense	6
Other Insurance Contracts \| Segment Reconciling Items
Insurance [Line Items]
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	69
Liability for Claims and Claims Adjustment Expense	84	44
Specialty Property & Casualty Program
Insurance [Line Items]
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	156
Specialty Property & Casualty Program \| Operating Segments
Insurance [Line Items]
Liability for Claims and Claims Adjustment Expense	197
Specialty Property & Casualty Program \| Commercial Auto
Insurance [Line Items]
Short-Duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	22
Short-Duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	28
Short-Duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	$ 6
Short-Duration Insurance Contracts, Historical Claims Duration, Year One	9.30%
Short-Duration Insurance Contracts, Historical Claims Duration, Year Two	2.90%
Short-Duration Insurance Contracts, Historical Claims Duration, Year Three	10.70%
Specialty Property & Casualty Program \| Commercial Auto \| Short-Duration Insurance Contract, Accident Year 2021
Insurance [Line Items]
Short-Duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 1	0	0
Short-Duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	0	0	0
Short-Duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Short-Duration Insurance Contract, Cumulative Number of Reported Claims	75
Specialty Property & Casualty Program \| Commercial Auto \| Short-Duration Insurance Contract, Accident Year 2022
Insurance [Line Items]
Short-Duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 8	8
Short-Duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	2	1
Short-Duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 3
Short-Duration Insurance Contract, Cumulative Number of Reported Claims	1,112
Specialty Property & Casualty Program \| Commercial Auto \| Short-Duration Insurance Contract, Accident Year 2023
Insurance [Line Items]
Short-Duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 19
Short-Duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	4
Short-Duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 10
Short-Duration Insurance Contract, Cumulative Number of Reported Claims	2,531
Specialty Property & Casualty Program \| Commercial Auto \| Operating Segments
Insurance [Line Items]
Short-Duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	$ 22
Specialty Property & Casualty Program \| Unallocated Loss Adjustment Expense Reserve \| Segment Reconciling Items
Insurance [Line Items]
Short-Duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	5
Specialty Property & Casualty Program \| Other Insurance Contracts
Insurance [Line Items]
Short-Duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	14
Short-Duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	16
Short-Duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	2
Short Duration Insurance Contract Liability For Unpaid Clams and Allocated Claim Adjustment Expense Subtotal For Separately Presented	$ 14
Short-Duration Insurance Contracts, Historical Claims Duration, Year One	3.10%
Short-Duration Insurance Contracts, Historical Claims Duration, Year Two	0.90%
Short-Duration Insurance Contracts, Historical Claims Duration, Year Three	0%
Specialty Property & Casualty Program \| Other Insurance Contracts \| Short-Duration Insurance Contract, Accident Year 2021
Insurance [Line Items]
Short-Duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 0	0	0
Short-Duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	0	0	$ 0
Short-Duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Short-Duration Insurance Contract, Cumulative Number of Reported Claims	0
Specialty Property & Casualty Program \| Other Insurance Contracts \| Short-Duration Insurance Contract, Accident Year 2022
Insurance [Line Items]
Short-Duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 0	0
Short-Duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	0	$ 0
Short-Duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 0
Short-Duration Insurance Contract, Cumulative Number of Reported Claims	646
Specialty Property & Casualty Program \| Other Insurance Contracts \| Short-Duration Insurance Contract, Accident Year 2023
Insurance [Line Items]
Short-Duration Insurance Contracts, Incurred Claims and Allocated Claim Adjustment Expense, Net	$ 16
Short-Duration Insurance Contracts, Cumulative Paid Claims and Allocated Claim Adjustment Expense, Net	2
Short-Duration Insurance Contracts, Incurred but Not Reported (IBNR) Claims Liability, Net	$ 8
Short-Duration Insurance Contract, Cumulative Number of Reported Claims	11,595
Specialty Property & Casualty Program \| Other Insurance Contracts \| Segment Reconciling Items
Insurance [Line Items]
Short-Duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	$ 14

Insurance Regulatory Restrict_2

Insurance Regulatory Restrictions Additional Details (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Average Annual Rate Of Return	5.86%	3.22%
Prescribed Discount Rate Percentage	5.10%
Minimum [Member]
Settlement Agreement Annual Restricted Payment Amount	$ 5
Maximum [Member]
Settlement Agreement Annual Restricted Payment Amount	7.5
Ambac Assurance [Member]
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	897	$ 598
Ambac Assurance [Member] \| Prescribed Or Permitted Additional Accounting Practices [Member]
Statutory Accounting Practices, Prescribed Practice, Amount	(24)	90
Everspan Indemnity
Statutory Accounting Practices, Statutory Capital and Surplus, Balance	$ 108	$ 107

Derivative Instruments - Summar

Derivative Instruments - Summary of Gross Fair Values of Individual Derivative Instruments (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 26	$ 28
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	26	27
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	35	38
Derivative Liabilities Gross Amount Of Collateral Cash And Securities Pledged Not Offset		38
Fair value of derivative liabilities	35
Net Amount, Derivative Assets	26	27
Net Amount, Derivative Liabilities	0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	0
Derivative Liability, Fair Value, Gross Liability	35	38
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Variable Interest Entity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	226	239
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	226	239
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,197	1,048
Derivative Liabilities Gross Amount Of Collateral Cash And Securities Pledged Not Offset		0
Fair value of derivative liabilities	0
Net Amount, Derivative Assets	0	239
Net Amount, Derivative Liabilities	1,197	1,048
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	226	0
Derivative Liability, Fair Value, Gross Liability	1,197	1,048
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	25	27
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	25	27
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	35	38
Fair value of derivative liabilities	35	38
Net Amount, Derivative Assets	25	27
Net Amount, Derivative Liabilities	0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Derivative Liability, Fair Value, Gross Liability	35	38
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Interest Rate Swaps [Member] \| Variable Interest Entity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	190	190
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	190	190
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,197	1,048
Net Amount, Derivative Assets	0	190
Net Amount, Derivative Liabilities	1,197	1,048
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	190
Derivative Liability, Fair Value, Gross Liability	1,197	1,048
Interest Rate Swaps [Member] \| Variable Interest Entity [Member] \| Level 3 [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Currency Swaps [Member] \| Variable Interest Entity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	36	49
Derivative Asset, Fair Value, Amount Offset Against Collateral	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	36	49
Net Amount, Derivative Assets	0	49
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	36	0
Warrant [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	1
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	1	1
Net Amount, Derivative Assets	$ 1	$ 1

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Derivative, Net Liability Position, Aggregate Fair Value	$ 35	$ 38
Derivative, Collateral, Right to Reclaim Cash	23	6
Collateral Already Posted, Aggregate Fair Value	50	54
Variable Interest Entity, Primary Beneficiary [Member] \| Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,662	1,573
Variable Interest Entity, Primary Beneficiary [Member] \| Interest Rate Swap One [Member]
Derivative [Line Items]
Derivative, Notional Amount	864	887
Variable Interest Entity, Primary Beneficiary [Member] \| Currency Swaps [Member]
Derivative [Line Items]
Derivative, Notional Amount	149	176
AFS [Member] \| Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount	167	337
AFS [Member] \| Interest Rate Swap One [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ 141	$ 989

Derivative Instruments - Summ_2

Derivative Instruments - Summary of Location and Amount of Gains and Losses of Derivative Contracts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (1)	$ 129	$ 22
Derivative, Gain (Loss) on Derivatives, Total Net	(64)	694	(128)
Variable Interest Entity [Member]
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(63)	565	(150)
Interest Rate Swaps [Member]
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(1)	65	13
Interest Rate Swaps [Member] \| Variable Interest Entity [Member]
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(62)	541	(152)
Currency Swaps [Member] \| Variable Interest Entity [Member]
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(1)	24	2
Futures Contracts [Member]
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	62	9
Warrant [Member]
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 0	$ 1	$ 0

Derivative Instruments - Summ_3

Derivative Instruments - Summary of Gross Principal Notional Outstanding for CDS Contracts (Detail) - Variable Interest Entity [Member] - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Interest Rate Swap [Member]
Ambac Rating
Derivative, Notional Amount	$ 1,662	$ 1,573
Interest Rate Swap One [Member]
Ambac Rating
Derivative, Notional Amount	864	887
Currency Swaps [Member]
Ambac Rating
Derivative, Notional Amount	$ 149	$ 176

Derivative Instruments - Summ_4

Derivative Instruments - Summarize Information by Major Category of CDS Contracts (Detail) $ in Millions	Dec. 31, 2023 USD ($)
Summary of information by major category of CDS contracts
Net derivative liabilities at fair value	$ 35

Derivative Instruments - Summ_5

Derivative Instruments - Summary of Notional Amounts of AFS's Trading Derivative Products (Detail) - AFS [Member] - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Interest Rate Swaps [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative, Notional Amount	$ 167	$ 337
Interest Rate Swaps-Pay-Fixed/Receive-Variable [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative, Notional Amount	$ 141	$ 989

Derivative Instruments - Summ_6

Derivative Instruments - Summary of Notional for VIE Derivatives Outstanding (Detail) - Variable Interest Entity, Primary Beneficiary [Member] - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Interest Rate Swaps [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative, Notional Amount	$ 1,662	$ 1,573
Interest Rate Swaps-Pay-Fixed/Receive-Variable [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative, Notional Amount	864	887
Currency Swaps [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative, Notional Amount	$ 149	$ 176

Financial Guarantee Insuranc_14

Financial Guarantee Insurance Contracts - Summary of Gross Premium Receivable Roll-Forward (Direct and Assumed Contracts) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Premiums Receivable, Gross	$ 290	$ 269	$ 323	$ 370
Public Finance [Member]
Premiums Receivable, Gross	140	150
Housing Revenue [Member] \| Public Finance [Member]
Premiums Receivable, Gross	139	148
Surveillance Category One [Member]
Premiums Receivable, Gross	210	217
Surveillance Category One [Member] \| Public Finance [Member]
Premiums Receivable, Gross	133	142
Surveillance Category One [Member] \| Housing Revenue [Member] \| Public Finance [Member]
Premiums Receivable, Gross	$ 131	$ 140

Intangible Assets (Details)

Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Intangible assets, less accumulated amortization	$ 307	$ 326
Finite-Lived Intangible Assets, Net	292	312
2018	30
2019	28
2020	26
2021	24
2022	22
Thereafter	162
Amortization of intangible assets	29	47	$ 55
Goodwill	70	61	46
Goodwill, Acquired During Period	9	15
Goodwill, Impaired, Accumulated Impairment Loss	0	0
License
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	14	14
Other Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	57	52
Finite-Lived Intangible Assets, Accumulated Amortization	10	6
Intangible assets, less accumulated amortization	47	47
2018	5
2019	4
2020	4
2021	4
2022	4
Thereafter	$ 26
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	5 years 3 months 18 days
Amortization of intangible assets	$ 4	3	3
Insurance Intangible Asset [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	1,258	1,247
Finite-Lived Intangible Assets, Accumulated Amortization	1,013	981
Intangible assets, less accumulated amortization	245	266
2018	26
2019	24
2020	22
2021	20
2022	18
Thereafter	$ 136
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	7 years 1 month 6 days
Amortization of intangible assets	$ 25	$ 44	$ 52

Variable Interest Entities - Ad

Variable Interest Entities - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2023 USD ($) Entity	Dec. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2022 USD ($) Entity	Dec. 31, 2021 USD ($)
Variable Interest Entities [Line Items]
Fixed income securities, amortized cost	$ 2,197	$ 2,197	$ 2,197	$ 2,041	$ 2,041	$ 2,041
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	40	40	40	31	31	31
Available-for-sale Securities	1,710	1,710	1,710	1,395	1,395	1,395
Restricted Cash	12	12	12	14	14	14	$ 5
Assets	8,428	8,428	8,428	7,973	7,973	7,973	12,303
Liabilities	6,997	6,997	6,997	6,647	6,647	6,647
Other Investments	475	475	475	568	568	568
Long-term debt	508	508	508	639	639	639
Derivative assets	26	26	26	27	27	27
Other assets	129	129	129	112	112	112
Accrued interest payable	475	475	475	427	427	427
Derivative liabilities	35	35	35	38	38	38
Other liabilities	199	$ 199	$ 199	201	$ 201	$ 201
Variable Interest Entity, Initial Consolidation, Gain (Loss)	4			37			$ 0
Consolidated Entities [Member]
Variable Interest Entities [Line Items]
Number of consolidated Variable Interest Entities		1	6		3	9	0
Number of DeConsolidated Variable Interest Entities		4			0		0
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Available-for-sale Securities	2,167	$ 2,167	$ 2,167	1,967	$ 1,967	$ 1,967
Restricted Cash	246	246	246	17	17	17	$ 2
Assets	4,394	4,394	4,394	4,054	4,054	4,054
Liabilities	4,404	4,404	4,404	4,160	4,160	4,160
Loans, Unpaid principal balance	1,787	1,787	1,787	1,977	1,977	1,977
Long-term Debt, Fair Value	2,710	2,710	2,710	2,788	2,788	2,788
Long-term debt, Unpaid principal balance	2,952	2,952	2,952	3,064	3,064	3,064
Long-term debt	2,967	2,967	2,967	3,107	3,107	3,107
Financing Receivable, after Allowance for Credit Loss	1,663	1,663	1,663	1,829	1,829	1,829
Derivative assets	226	226	226	239	239	239
Other assets	92	92	92	2	2	2
Long-term Debt, at par less amortized discount	258	258	258	319	319	319
Derivative liabilities	1,197	1,197	1,197	1,048	1,048	1,048
Other liabilities	5	5	$ 5	5	5	$ 5
Ambac UK [Member] \| Consolidated Entities [Member]
Variable Interest Entities [Line Items]
Number of consolidated Variable Interest Entities \| Entity			4			5
Ambac UK [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Available-for-sale Securities	2,072	2,072	$ 2,072	1,828	1,828	$ 1,828
Restricted Cash	245	245	245	1	1	1
Assets	4,296	4,296	4,296	3,896	3,896	3,896
Liabilities	4,244	4,244	4,244	3,836	3,836	3,836
Long-term Debt, Fair Value	2,710	2,710	2,710	2,788	2,788	2,788
Long-term debt	2,808	2,808	2,808	2,788	2,788	2,788
Financing Receivable, after Allowance for Credit Loss	1,663	1,663	1,663	1,829	1,829	1,829
Derivative assets	226	226	226	239	239	239
Other assets	90	90	90	0	0	0
Long-term Debt, at par less amortized discount	99	99	99	0	0	0
Derivative liabilities	1,197	1,197	1,197	1,048	1,048	1,048
Other liabilities	4	4	$ 4	0	0	$ 0
Ambac Assurance [Member] \| Consolidated Entities [Member]
Variable Interest Entities [Line Items]
Number of consolidated Variable Interest Entities \| Entity			2			4
Ambac Assurance [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Available-for-sale Securities	95	95	$ 95	139	139	$ 139
Restricted Cash	1	1	1	16	16	16
Assets	98	98	98	157	157	157
Liabilities	160	160	160	324	324	324
Long-term Debt, Fair Value	0	0	0	0	0	0
Long-term debt	159	159	159	319	319	319
Financing Receivable, after Allowance for Credit Loss	0	0	0	0	0	0
Derivative assets	0	0	0	0	0	0
Other assets	2	2	2	2	2	2
Long-term Debt, at par less amortized discount	159	159	159	319	319	319
Derivative liabilities	0	0	0	0	0	0
Other liabilities	1	1	1	5	5	5
Ambac Assurance Corporation [Member]
Variable Interest Entities [Line Items]
Long-term debt	508	508	508	639	639	639
Corporate Debt Securities [Member]
Variable Interest Entities [Line Items]
Fixed income securities, amortized cost	785	785	785	659	659	659
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4	4	4	1	1	1
Available-for-sale Securities	745	745	745	598	598	598
Corporate Debt Securities [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Available-for-sale Securities	2,072	2,072	2,072	1,828	1,828	1,828
Corporate Debt Securities [Member] \| Ambac UK [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Available-for-sale Securities	2,072	2,072	2,072	1,828	1,828	1,828
Corporate Debt Securities [Member] \| Ambac Assurance [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Available-for-sale Securities	0	0	0	0	0	0
Municipal Bonds [Member]
Variable Interest Entities [Line Items]
Fixed income securities, amortized cost	72	72	72	44	44	44
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1	1	0	0	0
Available-for-sale Securities	72	72	72	43	43	43
Municipal Bonds [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Fixed income securities, amortized cost	88	88	88	99	99	99
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	7	7	7	1	1	1
Available-for-sale Securities	95	95	95	96	96	96
Municipal Bonds [Member] \| Ambac UK [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Available-for-sale Securities	0	0	0	0	0	0
Municipal Bonds [Member] \| Ambac Assurance [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Available-for-sale Securities	$ 95	$ 95	$ 95	$ 96	$ 96	$ 96

Variable Interest Entities - Su

Variable Interest Entities - Summary of Fair Value of Fixed Income Securities, by Asset-Type, Held by Consolidated Variable Interest Entities (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Variable Interest Entities [Line Items]
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Assets	$ 351	$ 490
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Liabilities	836	840
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	20,861	21,639
Variable Interest Entity Nonconsolidated Carrying Amount Derivative Net Assets Or Liabilities	0
Fixed income securities, amortized cost	2,197	2,041
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	40	31
Variable Interest Entity [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity Nonconsolidated Carrying Amount Derivative Net Assets Or Liabilities		1
Corporate Obligations [Member]
Variable Interest Entities [Line Items]
Fixed income securities, amortized cost	785	659
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	4	1
Municipal Bonds [Member]
Variable Interest Entities [Line Items]
Fixed income securities, amortized cost	72	44
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	0
Municipal Bonds [Member] \| Variable Interest Entity [Member]
Variable Interest Entities [Line Items]
Fixed income securities, amortized cost	88	99
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	$ 7	$ 1

Variable Interest Entities - _2

Variable Interest Entities - Supplemental Information about Loans Held as Assets and Long-Term Debt Associated with Consolidated Variable Interest Entities (Detail) - Variable Interest Entity [Member] - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Variable Interest Entities [Line Items]
Long-term Debt, Fair Value	$ 2,710	$ 2,788
Loans, Unpaid principal balance	1,787	1,977
Long-term debt, Unpaid principal balance	$ 2,952	$ 3,064

Variable Interest Entities - _3

Variable Interest Entities - Summary of Carrying Amount of Assets, Liabilities and Maximum Exposure to Loss of Ambac's Variable Interests in Non-Consolidated Variable Interest Entities (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	$ 20,861	$ 21,639
Insurance Assets	351	490
Insurance Liabilities	836	840
Derivative Liabilities	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71	106
Fixed income securities, amortized cost	2,197	2,041
Collateralized Debt Obligations [Member]
Variable Interest Entities [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1	4
Fixed income securities, amortized cost	139	141
Residential Mortgage-Backed Securities [Member]
Variable Interest Entities [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	14	19
Fixed income securities, amortized cost	239	230
Municipal Bonds [Member]
Variable Interest Entities [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1	2
Fixed income securities, amortized cost	72	44
Variable Interest Entity [Member]
Variable Interest Entities [Line Items]
Derivative Liabilities		1
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Reclassification Adjustment from AOCI for Derecognition, before Tax	5	(1)	$ 5
Variable Interest Entity [Member] \| Municipal Bonds [Member]
Variable Interest Entities [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	(4)
Fixed income securities, amortized cost	88	99
Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	3,364	3,642
Insurance Assets	141	274
Insurance Liabilities	634	628
Derivative Liabilities	0	1
Global Structured Finance [Member] \| Residential Mortgage-Backed Securities [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	2,391	2,559
Insurance Assets	135	266
Insurance Liabilities	432	400
Derivative Liabilities	0	0
Global Structured Finance [Member] \| Other Consumer Asset-Backed [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	540	652
Insurance Assets	5	6
Insurance Liabilities	200	225
Derivative Liabilities	0	0
Global Structured Finance [Member] \| Other Debt Obligations [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	433	430
Insurance Assets	2	2
Insurance Liabilities	2	2
Derivative Liabilities	0	1
Global Public Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	17,498	17,997
Insurance Assets	209	216
Insurance Liabilities	202	212
Derivative Liabilities	$ 0	$ 0

Variable Interest Entities Vari

Variable Interest Entities Variable Interest Entity - Change in Fair Value of Assets and Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fixed income securities, amortized cost	$ 2,197	$ 2,041
Long-term debt	508	639
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	40	31
Variable Interest Entity Change in Fair Value of Assets and Liabilities	4	0	$ 4
Realized Investment Gains (Losses)	(22)	31	7
Variable Interest Entity, Initial Consolidation, Gain (Loss)	4	37	0
Variable Interest Entity, Measure of Activity, Income or Loss before Tax	3	21	7
Assets	8,428	7,973	12,303
Liabilities	6,997	6,647
Variable Interest Entity [Member]
Long-term debt	2,967	3,107
Loans, Unpaid principal balance	1,787	1,977
Long-term debt, Unpaid principal balance	2,952	3,064
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Reclassification Adjustment from AOCI for Derecognition, before Tax	0	(1)	1
Gross Investment Income, Operating	7	(4)	6
Realized Investment Gains (Losses)	1	2	2
Interest Expense, Long-term Debt	(12)	(12)	(6)
Other Expenses	(1)	(1)	(1)
Assets	4,394	4,054
Liabilities	4,404	4,160
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Reclassification Adjustment from AOCI for Derecognition, before Tax	$ 5	$ (1)	$ 5

Variable Interest Entities Va_2

Variable Interest Entities Variabile Interest Entities - Carry Value of Secured Notes from LSNI (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Long-term debt	$ 508	$ 639
Ambac Assurance Corporation [Member]
Long-term debt	$ 508	$ 639

Variable Interest Entities Spec

Variable Interest Entities Special Purpose Entities, including Variable Interest Entities - Summary of Assets and Liabilities (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2023 USD ($) Entity	Dec. 31, 2022 USD ($)	Dec. 31, 2022 USD ($) Entity	Dec. 31, 2021 USD ($)
Fixed income securities, amortized cost	$ 2,197	$ 2,197	$ 2,041	$ 2,041
Available-for-sale Securities	1,710	1,710	1,395	1,395
Restricted Cash	12	12	14	14	$ 5
Derivative assets	26	26	27	27
Other assets	129	129	112	112
Assets	8,428	8,428	7,973	7,973	12,303
Accrued interest payable	475	475	427	427
Long-term debt	508	508	639	639
Derivative liabilities	35	35	38	38
Other liabilities	199	199	201	201
Liabilities	6,997	6,997	6,647	6,647
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71	71	106	106
Corporate Debt Securities [Member]
Fixed income securities, amortized cost	785	785	659	659
Available-for-sale Securities	745	745	598	598
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	44	44	63	63
Municipal Bonds [Member]
Fixed income securities, amortized cost	72	72	44	44
Available-for-sale Securities	72	72	43	43
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1	1	2	2
Variable Interest Entity [Member]
Available-for-sale Securities	2,167	2,167	1,967	1,967
Restricted Cash	246	246	17	17	$ 2
Loans, at fair value	1,663	1,663	1,829	1,829
Derivative assets	226	226	239	239
Other assets	92	92	2	2
Assets	4,394	4,394	4,054	4,054
Long-term Debt	2,710	2,710	2,788	2,788
Long-term Debt, at par less amortized discount	258	258	319	319
Long-term debt	2,967	2,967	3,107	3,107
Derivative liabilities	1,197	1,197	1,048	1,048
Cash Collateral Payable	235	235	0	0
Other liabilities	5	5	5	5
Liabilities	4,404	4,404	4,160	4,160
Loans, Unpaid principal balance	1,787	1,787	1,977	1,977
Long-term debt, Unpaid principal balance	2,952	2,952	3,064	3,064
Variable Interest Entity [Member] \| Ambac UK [Member]
Available-for-sale Securities	2,072	2,072	1,828	1,828
Restricted Cash	245	245	1	1
Loans, at fair value	1,663	1,663	1,829	1,829
Derivative assets	226	226	239	239
Other assets	90	90	0	0
Assets	4,296	4,296	3,896	3,896
Long-term Debt	2,710	2,710	2,788	2,788
Long-term Debt, at par less amortized discount	99	99	0	0
Long-term debt	2,808	2,808	2,788	2,788
Derivative liabilities	1,197	1,197	1,048	1,048
Cash Collateral Payable	235	235	0	0
Other liabilities	4	4	0	0
Liabilities	4,244	4,244	3,836	3,836
Variable Interest Entity [Member] \| Ambac Assurance [Member]
Available-for-sale Securities	95	95	139	139
Restricted Cash	1	1	16	16
Loans, at fair value	0	0	0	0
Derivative assets	0	0	0	0
Other assets	2	2	2	2
Assets	98	98	157	157
Long-term Debt	0	0	0	0
Long-term Debt, at par less amortized discount	159	159	319	319
Long-term debt	159	159	319	319
Derivative liabilities	0	0	0	0
Cash Collateral Payable	0	0	0	0
Other liabilities	1	1	5	5
Liabilities	160	160	324	324
Variable Interest Entity [Member] \| Corporate Debt Securities [Member]
Available-for-sale Securities	2,072	2,072	1,828	1,828
Variable Interest Entity [Member] \| Corporate Debt Securities [Member] \| Ambac UK [Member]
Available-for-sale Securities	2,072	2,072	1,828	1,828
Variable Interest Entity [Member] \| Corporate Debt Securities [Member] \| Ambac Assurance [Member]
Available-for-sale Securities	0	0	0	0
Variable Interest Entity [Member] \| Municipal Bonds [Member]
Fixed income securities, amortized cost	88	88	99	99
Available-for-sale Securities	95	95	96	96
Debt Securities, Trading	0	0	43	43
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	0	(4)	(4)
Variable Interest Entity [Member] \| Municipal Bonds [Member] \| Ambac UK [Member]
Available-for-sale Securities	0	0	0	0
Debt Securities, Trading	0	0	0	0
Variable Interest Entity [Member] \| Municipal Bonds [Member] \| Ambac Assurance [Member]
Available-for-sale Securities	95	95	96	96
Debt Securities, Trading	$ 0	$ 0	$ 43	$ 43
Consolidated Entities [Member]
Number of consolidated Variable Interest Entities	1	6	3	9	0
Consolidated Entities [Member] \| Ambac UK [Member]
Number of consolidated Variable Interest Entities \| Entity		4		5
Consolidated Entities [Member] \| Ambac Assurance [Member]
Number of consolidated Variable Interest Entities \| Entity		2		4

Long-Term Debt (Details)

Long-Term Debt (Details) - USD ($) $ in Millions	12 Months Ended
Long-Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jul. 06, 2021
Debt Instrument [Line Items]
Long-term debt	$ 508	$ 639
Debt Instrument, Interest Rate, Effective Percentage	6.60%
Net realized gains on extinguishment of debt	$ 0	81	$ 33
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	519
Long-term Debt, Maturities, Repayments of Principal in Year Two	0
Long-term Debt, Maturities, Repayments of Principal in Year Three	0
Long-term Debt, Maturities, Repayments of Principal in Year Four	0
Long-term Debt, Maturities, Repayments of Principal in Year Five	0
Paydown of Ambac Note			1,641
Long-term Debt, Maturities, Repayments of Principal after Year Five	41
5.1% Junior Surplus Notes, General Account Due 2020 Plus Accrued Interest	$ 475
Tier 2 Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	8.50%
Debt Instrument, Interest Rate, Effective Percentage	9.90%
Debt Instrument, Face Amount	$ 0
Paid-in-Kind Interest	0	49
5.1% Junior Surplus Notes, General Account Due 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Issued, Principal			280
Ambac Assurance Corporation [Member]
Debt Instrument [Line Items]
Long-term debt	508	639
Long-term Debt, Gross	560	706
Debt Instrument, Unamortized Discount (Premium), Net	(52)	(67)
Ambac Assurance Corporation [Member] \| 5.1% Surplus Notes, General Account, Due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt	491	477
Long-term Debt, Gross	519	519
Debt Instrument, Unamortized Discount (Premium), Net	(28)	(42)
Ambac Assurance Corporation [Member] \| Tier 2 Notes [Member]
Debt Instrument [Line Items]
Long-term debt	0	146
Long-term Debt, Gross	0	146
Debt Instrument, Unamortized Discount (Premium), Net	0	0
Ambac Assurance Corporation [Member] \| Sitka AAC Note
Debt Instrument [Line Items]
Net realized gains on extinguishment of debt	$ 53
Ambac UK [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	0%
Long-term debt	$ 17	16
Long-term Debt, Gross	41	41
Debt Instrument, Unamortized Discount (Premium), Net	$ (24)	(25)
Debt Instrument, Interest Rate, Effective Percentage	7.40%
Sitka Holdings, LLC \| LIBOR + 4.5% Senor Secured Notes Due 2026
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 1,175
5.1% Surplus Notes, General Account, Due 2020 [Member]
Debt Instrument [Line Items]
Net realized gains on extinguishment of debt		134
Debt Instrument, Repurchased During Period	$ 266
5.1% Junior Surplus Notes, General Account Due 2020 [Member]
Debt Instrument [Line Items]
Net realized gains on extinguishment of debt			$ 33
Consolidated Variable Interest Entities [Member]
Debt Instrument [Line Items]
Unpaid Principal Amount Of Fixed Rate Debt Accounted For Under Fair Value Option	3,655	$ 3,388
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	0
Long-term Debt, Maturities, Repayments of Principal in Year Two	0
Long-term Debt, Maturities, Repayments of Principal in Year Three	0
Long-term Debt, Maturities, Repayments of Principal in Year Four	0
Long-term Debt, Maturities, Repayments of Principal in Year Five	0
Long-term Debt, Maturities, Repayments of Principal after Year Five	$ 3,655
Consolidated Variable Interest Entities [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	0%	0%
Consolidated Variable Interest Entities [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	22.20%	7.93%
London Interbank Offered Rate (LIBOR) [Member] \| LIBOR + 4.5% Senor Secured Notes Due 2026
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				4.50%

Revenue from Contract with Cu_3

Revenue from Contract with Customer (Details) $ in Millions	12 Months Ended
Revenue from Contract with Customer (Details) $ in Millions	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract with Customer, Asset, after Allowance for Credit Loss	$ 95	$ 5
Contract with Customer, Liability	1	1
Contract with Customer, Liability, Revenue Recognized	1	1	$ 1
Contract with Customer, Receivable, after Allowance for Credit Loss	10	7
Revenue from Contract with Customer, Excluding Assessed Tax	51	31	26
Contract with Customer, Performance Obligation Satisfied in Previous Period	5	6	8
Variable Interest Entity [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract with Customer, Asset, after Allowance for Credit Loss	87
Contract with Customer, Liability	0
Employer Stop Loss
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	11	9	8
Affinity Products
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	22	19	18
Commercial Auto
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	12	2
Marine
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3	0
Professional Liability
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3
Product and Service, Other
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 1	$ 0	$ 0
Minimum [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Employee Stop Loss Time When Base Commissions Recognized Begin and End In Months	17
Maximum [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Employee Stop Loss Time When Base Commissions Recognized Begin and End In Months	20

Comprehensive Income - Schedule

Comprehensive Income - Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ (253)	$ 58
Other comprehensive income before reclassifications	(74)	296
Amounts reclassified from accumulated other comprehensive income	19	(15)
Income Tax Expense (Benefit)	(7)	(2)	$ (18)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	93	(310)
Ending Balance	(160)	(253)	58
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(71)	154
Other comprehensive income before reclassifications	(31)	211
Amounts reclassified from accumulated other comprehensive income	21	(14)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	51	(225)
Ending Balance	(20)	(71)	154
Accumulated Translation Adjustment [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(184)	(100)
Other comprehensive income before reclassifications	(40)	85
Amounts reclassified from accumulated other comprehensive income	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	40	(85)
Ending Balance	(144)	(184)	(100)
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(1)	(1)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0	0
Ending Balance	(1)	(1)	(1)
Other Postretirement Benefits Plan [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	3	4
Other comprehensive income before reclassifications	(3)	0
Amounts reclassified from accumulated other comprehensive income	(1)	(1)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	2	(1)
Ending Balance	$ 5	$ 3	$ 4

Comprehensive Income - Schedu_2

Comprehensive Income - Schedule of Amounts Reclassed Out of Each Component of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	$ (7)	$ (2)	$ (18)
Net of tax and noncontrolling interest	8	525	$ (28)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	19	(15)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized investment gains	22	(17)
Net of tax and noncontrolling interest	21	(14)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	21	(14)
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, before Tax	0	0
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, after Tax	0	0
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax and noncontrolling interest	19	(15)
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	2	(3)
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, Tax	0
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Accumulated Gain (Loss), Financial Liability, Fair Value Option, Including Portion Attributable to Noncontrolling Interest [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, Tax		0
Other Postretirement Benefits Plan [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(1)	(1)
Other Postretirement Benefits Plan [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	0	0
Prior service cost	(1)	(1)
Actuarial gains (losses)	(1)	0
Total before tax	(1)	(1)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ (1)	$ (1)

Net Income Per Share - Addition

Net Income Per Share - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended	12 Months Ended			21 Months Ended
	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2023	May 05, 2022	Mar. 29, 2022	Apr. 30, 2013
Schedule Of Earnings Per Share [Line Items]
Common Stock, Shares, Outstanding	45,195,370	45,195,370			45,195,370
Number of new common stock issued	46,659,144	46,659,144	46,658,990		46,659,144
Common Stock, Par or Stated Value Per Share								$ 0.01
Warrant exercised		1,503	0	132
Stock Issued During Period, Shares, New Issues		29	0	4
Net Income (Loss) Available to Common Stockholders, Basic		$ 8	$ 525	$ (28)
Noncontrolling Interest, Change in Redemption Value		5	3	$ (12)
Stock Repurchase Program, Authorized Amount						$ 15	$ 20
Stock Repurchased During Period, Shares	325,068				1,930,384
Payments for Repurchase of Common Stock		$ 5	$ 14		$ 19
Common Stock Repurchase
Schedule Of Earnings Per Share [Line Items]
Payments for Common Stock per share					$ 9.70
Stock Repurchase Program, Remaining Authorized Repurchase Amount						$ 16
Common Stock [Member]
Schedule Of Earnings Per Share [Line Items]
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture		221,613
Noncontrolling Interest, Change in Redemption Value		$ 0

Net Income Per Share - Reconcil

Net Income Per Share - Reconciliation of Common Shares Used for Basic and Diluted Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of common shares and potential dilutive shares used for diluted earnings per share	46,540,706	46,414,830	46,535,001
Weighted Average Number of Shares Outstanding, Basic	45,636,649	45,719,906	46,535,001
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	4,877,617	4,877,653
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	135,058	177,119	475,333
Performance Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0	700,915
Performance Shares [Member]
Effect of potential dilutive shares:
Effect of potential dilutive shares	739,305	550,730	0
Restricted Stock Units (RSUs) [Member]
Effect of potential dilutive shares:
Effect of potential dilutive shares	164,752	144,194	0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Tax Credit Carryforward [Line Items]
Deferred Tax Liabilities, Net	$ 19	$ 15
NOL allocated amount	3,400
AFG [Member]
Tax Credit Carryforward [Line Items]
NOL allocated amount	$ 1,640

Income Taxes - Significant Port

Income Taxes - Significant Portions of Deferred Tax Liabilities and Deferred Tax Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred Tax Assets, Net of Valuation Allowance	$ 58	$ 70
Deferred tax assets:
Net operating loss and capital carryforward	714	725
Deferred Tax Asset, Interest Carryforward	58	66
Deferred Tax Assets, Investments	0	6
Loss reserves	42	38
Deferred Tax Assets, Operating Loss Carryforwards, State and Local	8	8
Deferred Tax Assets, Debentures	22	15
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation	5	6
Other	4	4
Sub total deferred tax assets	853	867
Valuation allowance	795	796
Insurance intangible	51	56
Variable interest entities	0	4
Unearned premiums and credit fees	23	24
Other	3	1
Deferred Tax Liabilities, Gross	77	85
Deferred Tax Liabilities, Net	$ 19	$ 15

Income Taxes Income Taxes - Pro

Income Taxes Income Taxes - Provision for Income Taxes Charged To Income From Continuing Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Provision for Income Taxes [Line Items]
Current Income Tax Expense (Benefit)	$ 8	$ 6	$ 12
Deferred Income Taxes and Tax Credits	(2)
Deferred Income Tax Expense (Benefit)	(1)	(4)	6
Income tax expense (benefit)	7	2	18
Deferred Foreign Income Tax Expense (Benefit)	1	(4)	6
Current State and Local Tax Expense (Benefit)	1	0	2
Current Foreign Tax Expense (Benefit)	$ 8	$ 7	$ 10

Income Taxes Income Taxes - Eff

Income Taxes Income Taxes - Effect of Income Taxes on Net Income and Stockholders' Equity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Expense (Benefit) [Roll Forward]
Income tax expense (benefit)	$ 7	$ 2	$ 18
Net Unrealized Losses On Securities Tax Effect	12	(47)	(3)
Valuation Allowances And Reserves Charged To Equity	(9)	41	(1)
Income Tax Effects Allocated Directly to Equity	2	(6)	(2)
Change in retirement benefits Tax Effect	(1)	0	0
Credit Risk Changes to Fair Value Options Tax Effect	0	0	0
Income Tax Effects Allocated Directly to Equity, Other	$ 9	$ (4)	$ 16

Income Taxes Income Taxes - E_2

Income Taxes Income Taxes - Effective Tax Rates Differing From Prevailing Federal Corporate Income Tax Rates (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Effective Tax Rates [Line Items]
Tax on income from continuing operations at statutory rate	$ 3	$ 110	$ 0
Tax on income from continuing operations at statutory rate,tax rate	21%	21%	21%
Tax-exempt interest	$ 0	$ (1)	$ (2)
Tax-exempt interest, tax rate	0%	0%	(114.00%)
Derivative, Gain (Loss) on Derivative, Net	$ (1)	$ 129	$ 22
Valuation allowance	$ 2	$ (131)	$ (4)
Valuation allowance, tax rate	13%	(25.00%)	(230.00%)
Other, net	$ 4	$ (4)	$ 1
Foreign taxes	$ 9	$ 4	$ 8
Foreign taxes, tax rate	70%	1%	448%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	$ 0	$ (1)	$ 14
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent	(1.00%)	0%	794%
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Percent	118%	0%	0%
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount	$ 15	$ 0	$ 0
Other, net, tax rate	35%	(1.00%)	72%
Income tax expense (benefit)	$ 7	$ 2	$ 18
Effective Income Tax Rate Reconciliation, Percent	60%	1%	991%
Effective Tax Rate Reconciliation, Variable Interest Entities	$ (24)	$ 25
Effective Tax Rate Reconciliation, Variable Interest Entities, Percent	(197.00%)	5%
Futures Contracts [Member]
Reconciliation of Effective Tax Rates [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 0	$ 62	$ 9
Interest Rate Swaps [Member]
Reconciliation of Effective Tax Rates [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(1)	65	13
Variable Interest Entity, Primary Beneficiary [Member]
Reconciliation of Effective Tax Rates [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(63)	565	(150)
Variable Interest Entity, Primary Beneficiary [Member] \| Currency Swaps [Member]
Reconciliation of Effective Tax Rates [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(1)	24	2
Variable Interest Entity, Primary Beneficiary [Member] \| Interest Rate Swaps [Member]
Reconciliation of Effective Tax Rates [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (62)	$ 541	$ (152)

Income Taxes Income Taxes - Rec

Income Taxes Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) $ in Millions	Dec. 31, 2023 USD ($)
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits	$ 0

Income Taxes Income Taxes - NOL

Income Taxes Income Taxes - NOL Usage Table (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	$ 3,400
Ambac Assurance [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	1,760
AFG [Member]
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	$ 1,640
Minimum [Member] \| Ambac Assurance [Member]
Net Income Loss Reconciliation [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2030
Maximum [Member] \| Ambac Assurance [Member]
Net Income Loss Reconciliation [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2042

Income Taxes Schedule of Income

Income Taxes Schedule of Income Before Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule of Income Before Income Tax, Domestic and Foreign [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Domestic	$ (29)	$ 511	$ (32)
Income (Loss) from Continuing Operations before Income Taxes, Foreign	41	13	34
Pretax income (loss)	$ 12	$ 525	$ 2

Employment Benefit Plans Postre

Employment Benefit Plans Postretirement Health Care and Other Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Postemployment Benefits, Period Expense	$ 1	$ 2	$ 1
Unfunded Accumulated Postretirement Benefit Obligations Determined By Company	$ 8
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	4.75%	5%
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	$ 0
Defined Benefit Plan, Expected Future Benefit Payment, Year Two	0
Defined Benefit Plan, Expected Future Benefit Payment, Year Three	1
Defined Benefit Plan, Expected Future Benefit Payment, Year Four	1
Defined Benefit Plan, Expected Future Benefit Payment, Year Five	1
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter	3
Defined Benefit Plan, Benefit Obligation	$ 6
Maximum [Member]
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year	5.50%
Minimum [Member]
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year	4.50%

Employment Benefit Plans Saving

Employment Benefit Plans Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	2%
Defined Contribution Plan, Cost	$ 1	$ 1	$ 1
Minimum [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	100%
Maximum [Member]
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	50%
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent	3%

Employment Benefit Plans Stock

Employment Benefit Plans Stock Compensation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense	$ 17	$ 17	$ 14
Total stock-based compensation (after-tax)	$ 17	$ 17	11
Common stock, shares authorized	130,000,000	130,000,000
2013 Plan
Share-based compensation expense [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	4,000,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	4,000,000
2021 Plan
Share-based compensation expense [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,475,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,475,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense	$ 5	$ 5	5
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense	$ 12	$ 12	$ 10

Employment Benefit Plans Restri

Employment Benefit Plans Restricted Stock Units (Details)	12 Months Ended
Employment Benefit Plans Restricted Stock Units (Details)	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payment, Tax Withholding, Share-based Payment Arrangement \| $	$ 5,000,000	$ 4,000,000	$ 6,000,000
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Restricted Stock Units Vested Number	402,027	385,087
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	538,163
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	634,312	538,163
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payment, Tax Withholding, Share-based Payment Arrangement \| $	$ 49,870
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	923,250
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	415,416
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	300,164
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(2,163)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	1,036,339	923,250
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value \| $ / shares	$ 15.94
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares	15.72	$ 12.48	$ 17.39
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value \| $ / shares	16.28
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value \| $ / shares	16.97
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value \| $ / shares	$ 15.75	$ 15.94
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized \| $	$ 6,000,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	2 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value \| $	$ 5,000,000	$ 4,000,000	$ 4,000,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payment, Tax Withholding, Share-based Payment Arrangement \| $	$ 231,645
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	918,951
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	479,079
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	(525,212)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(1,289)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	1,019,071	918,951
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value \| $ / shares	$ 15.67
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares	17.72	$ 13.44	$ 18.67
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value \| $ / shares	18.90
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value \| $ / shares	17.72
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value \| $ / shares	$ 15.52	$ 15.67
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized \| $	$ 10,000,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition	1 year 8 months 12 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value \| $	$ 8,000,000	$ 5,000,000	$ 10,000,000
Performance Shares [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
2013 RSU Award First Vesting Percent	240%
Performance Shares [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
2013 RSU Award First Vesting Percent	0%
Long-term Incentive Compensation [Domain] \| Restricted Stock Units (RSUs) [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU Award Vesting Period	3
Long-term Incentive Compensation [Domain] \| Restricted Stock Units (RSUs) [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU Award Vesting Period	2

Employment Benefit Plans Perfor

Employment Benefit Plans Performance Units (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
PerformanceAwardsSettlementPeriod	75 days
Payment, Tax Withholding, Share-based Payment Arrangement	$ 5,000,000	$ 4,000,000	$ 6,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	538,163
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	634,312	538,163
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
PSU Payout Percentage Upon Termination	100%
2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Shareholder Return Modifier	10%
2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Shareholder Return Modifier	20%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Shareholder Return Modifier	2,500%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Shareholder Return Modifier	7,500%
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSUUnrecognizedCompensationYearstoGo	1 year 8 months 12 days
Target Units	100%
Payment, Tax Withholding, Share-based Payment Arrangement	$ 231,645
PerformanceStockUnitsUnrecognizedCompensationExpense	$ 10,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	918,951
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	479,079
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	(525,212)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(1,289)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	1,019,071	918,951
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 15.67
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	17.72	$ 13.44	$ 18.67
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	18.90
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	17.72
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 15.52	$ 15.67
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Period Increase (Decrease)	147,542
ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIncrease(Decrease)WeightedAverageGrantDateFairValue	$ 19.50
Performance Shares [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	0%
Performance Shares [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	240%
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSUUnrecognizedCompensationYearstoGo	2 years
Payment, Tax Withholding, Share-based Payment Arrangement	$ 49,870
PerformanceStockUnitsUnrecognizedCompensationExpense	$ 6,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	923,250
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	415,416
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	300,164
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	(2,163)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	1,036,339	923,250
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 15.94
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	15.72	$ 12.48	$ 17.39
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	16.28
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	16.97
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 15.75	$ 15.94

Leases Statement (Details)

Leases Statement (Details) - USD ($) $ in Millions	12 Months Ended
Leases Statement (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Lessor, Operating Lease, Term of Contract	6 years
Operating Leases, Future Minimum Payments Receivable, Remainder of Fiscal Year	$ 1
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	4
Lessee, Operating Lease, Liability, Payments, Due Year Two	5
Lessee, Operating Lease, Liability, Payments, Due Year Three	5
Lessee, Operating Lease, Liability, Payments, Due Year Four	5
Lessee, Operating Lease, Liability, Payments, Due Year Five	5
Lessee, Operating Lease, Liability, Payments, Due after Year Five	5
Lessee, Operating Lease, Liability, Payments, Due	28
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(6)
Operating Lease, Right-of-Use Asset	19	$ 21
Operating Lease, Payments	5	5
Operating Lease, Expense	4	4
Short-Term Lease, Cost	0	0
Variable Lease, Cost	1	0
Sublease Income	(1)	(1)
Lease, Cost	4	4
Operating Lease, Liability	$ 22	$ 25
Operating Lease, Weighted Average Remaining Lease Term	6 years 1 month 6 days	6 years 9 months 18 days
Operating Lease, Weighted Average Discount Rate, Percent	7.90%	7.80%
Operating Leases, Future Minimum Payments Receivable, in Two Years	$ 1
Operating Leases, Future Minimum Payments Receivable, in Three Years	1
Operating Leases, Future Minimum Payments Receivable, in Four Years	1
Operating Leases, Future Minimum Payments Receivable, in Five Years	1
Operating Leases, Future Minimum Payments, Due Thereafter	1
Lessor, Operating Lease, Payments to be Received	8
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 1	$ 0
Minimum [Member]
Lessee Operating Lease Remaining Lease Term	1 year
Maximum [Member]
Lessee Operating Lease Remaining Lease Term	9 years

Leases (Details)

Leases (Details) $ in Millions	Dec. 31, 2023 USD ($)
Statement of Financial Position [Abstract]
Lessor, Operating Lease, Payments to be Received	$ 8

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Loss Contingencies [Line Items]
Retiree Committee Asserted Pension Liabilities	$ 58,500
AAC Asserted Pension Liability Overstatement	$ 9,000

Schedule I - Summary Of Investm

Schedule I - Summary Of Investments (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties, Cost	$ 2,652
Investments	2,664
Short-term investments, at cost (approximates fair value)	2,197	$ 2,041
Other Investments	475	568
Available-for-sale Securities	1,710	1,395
Investments	2,664	2,593
Municipal Bonds [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	72	44
Available-for-sale Securities	72	43
Corporate Debt Securities [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	785	659
Available-for-sale Securities	745	598
Debt Security, Government, Non-US [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	105	85
Available-for-sale Securities	100	76
Residential Mortgage-Backed Securities [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	239	230
Available-for-sale Securities	250	238
Collateralized Debt Obligations [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	139	141
Available-for-sale Securities	139	137
Asset-backed Securities [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	301	227
Available-for-sale Securities	303	224
Short-term Investments [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	426	507
Available-for-sale Securities	426	507
U S Government Obligations [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	85
Available-for-sale Securities	82
US Government Debt Securities [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	85	68
Available-for-sale Securities	82	65
ShortTermInvestmentsMember, including Pledged
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	452
Available-for-sale Securities	452
Corporate Obligations, Excluding Related Party Investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	785
Available-for-sale Securities	745
Other Investments [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	432
Available-for-sale Securities	463
Other Investments [Member] \| Fixed Income Funds
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Available-for-sale Securities	475
Commercial Mortgage Backed Securities [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	19	15
Available-for-sale Securities	19	0
Available-for-sale Securities [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	24
Available-for-sale Securities	27
Fixed Income Securities [Member]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Short-term investments, at cost (approximates fair value)	1,744	$ 1,469
Fair Value Amount, Excluding Related Party Investments [Domain]
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Investments	$ 2,652

Schedule II - Condensed Financi

Schedule II - Condensed Financial Information of Registrant (Parent Company Only) - Condensed Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, shares issued	46,659,144	46,658,990
Treasury Stock, Common, Shares	1,463,774	1,685,233
Common Stock, Shares, Outstanding	45,195,370
Assets:
Debt Securities, Available-for-sale	$ 1,710	$ 1,395
Short-term investments, at cost (approximates fair value)	2,197	2,041
Other Investments	475	568
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	0
Investments, Total	2,664	2,593
Investment income due and accrued	14	10
Other assets	129	112
Assets	8,428	7,973	$ 12,303
Liabilities:
Liabilities	6,997	6,647
Stockholders' equity (deficit):
Preferred Stock, Value, Issued	0	0
Common stock	0	0
Additional paid-in capital	292	274
Accumulated other comprehensive income (loss)	(160)	(253)	58
Retained earnings	1,246	1,245
Common stock held in treasury at cost	(17)	(15)
Total Ambac Financial Group, Inc. stockholders’ equity	1,362	1,252
Total liabilities, redeemable noncontrolling interest and stockholders’ equity	8,428	7,973
Short-term investments, amortized cost	426	507
Ambac Financial Group, Inc Parent Company Only [Member]
Assets:
Debt Securities, Available-for-sale	14	12
Short-term investments, at cost (approximates fair value)	14	13
Other Investments	18	16
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Investments, Total	188	203
Cash	0	3
Investment in subsidiaries	1,150	1,029
Investment income due and accrued	1	1
Other assets	24	19
Assets	1,365	1,255
Taxes Payable, Current	0	1
Liabilities:
Accounts payable and other liabilities	3	3
Liabilities	4	3
Stockholders' equity (deficit):
Preferred Stock, Value, Issued	0	0
Common stock	0	0
Additional paid-in capital	292	274
Accumulated other comprehensive income (loss)	(160)	(253)
Retained earnings	1,246	1,245
Common stock held in treasury at cost	(17)	(15)
Total Ambac Financial Group, Inc. stockholders’ equity	1,362	1,252	$ 1,038	$ 1,080
Total liabilities, redeemable noncontrolling interest and stockholders’ equity	1,365	1,255
Short-term investments, amortized cost	156	175
Short-term Investments [Member]
Assets:
Debt Securities, Available-for-sale	426	507
Short-term investments, at cost (approximates fair value)	426	507
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Short-term Investments [Member] \| Ambac Financial Group, Inc Parent Company Only [Member]
Assets:
Short-term investments, at cost (approximates fair value)	$ 156	$ 175

Schedule II - Condensed Finan_2

Schedule II - Condensed Financial Information of Registrant (Parent Company Only) - Condensed Statement of Total Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Other income	$ 11	$ 10	$ 1
Net investment gains (losses), including impairments	22	(31)	(7)
Total revenues and other income	269	505	282
General and Administrative Expense	156	141	111
Expenses:
Operating Expenses	155	139	110
Income tax expense (benefit)	(7)	(2)	(18)
Net income (loss) attributable to common stockholders	4	522	(17)
Other comprehensive income, after tax:
Net income	5	522	(16)
Unrealized gains (losses) on securities, net of deferred income taxes of $0	51	(225)	(12)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	40	(85)	(8)
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Reclassification Adjustment from AOCI for Derecognition, after Tax	0	0	(1)
Total other comprehensive income (loss), net of income tax	93	(310)	(21)
Total comprehensive income attributable to common stockholders	96	212	(38)
Derivative, Gain (Loss) on Derivative, Net	(1)	129	22
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax	2	(6)	(2)
Other Comprehensive Income (Loss), Foreign Currency Translation Gain (Loss) Arising During Period, Tax	0	0	0
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Reclassification Adjustment from AOCI for Derecognition, Tax	0	0	0
Revenues:
Investment income	9	10	10
Other income	0	0	0
Net investment gains (losses), including impairments	0	14	5
Total revenues and other income	9	(2)	5
General and Administrative Expense	22	17	19
Expenses:
Operating Expenses	22	17	19
Pretax income (loss)	(13)	(20)	(14)
Income tax expense (benefit)	1	0	(2)
Income (loss) before equity pick-up of net income (loss) of subsidiaries	11	19	16
Equity in undistributed net income (loss) of subsidiaries	15	542	(1)
Net income (loss) attributable to common stockholders	4	522	(17)
Other comprehensive income, after tax:
Net income	4	522	(17)
Unrealized gains (losses) on securities, net of deferred income taxes of $0	51	(225)	(12)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	40	(85)	(8)
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Reclassification Adjustment from AOCI for Derecognition, after Tax	0	0	(1)
Changes to postretirement benefit, net of tax	2	(1)	(1)
Total other comprehensive income (loss), net of income tax	93	(310)	(21)
Total comprehensive income attributable to common stockholders	96	212	(38)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Plan Amendments, Tax Effect	0	0	$ 0
Derivative, Gain (Loss) on Derivative, Net	$ 0	$ 1

Schedule II - Condensed Finan_3

Schedule II - Condensed Financial Information of Registrant (Parent Company Only) - Condensed Statements of Stockholders' Equity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income, net of income tax	$ 98	$ 212	$ (38)
Stock-based compensation	(17)	(17)	(14)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	(5)	(4)	(6)
Ending balance	1,415	1,305	1,098
Stockholders' Equity Attributable to Parent	1,362	1,252
Noncontrolling Interest, Change in Redemption Value	5	3	(12)
Treasury Stock, Value, Acquired, Cost Method	5	(14)
AMPS Impact on Stockholders Equity		(8)
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income, net of income tax	4	521	(17)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	(8)	(5)	(4)
Ending balance	1,246	1,245	726
Noncontrolling Interest, Change in Redemption Value	5	3	(12)
AMPS Impact on Stockholders Equity		1
AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income, net of income tax	93	(310)	(21)
Ending balance	(160)	(253)	58
Noncontrolling Interest, Change in Redemption Value	0
Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ending balance	0	0	0
Noncontrolling Interest, Change in Redemption Value	0
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ending balance	0	0	0
Noncontrolling Interest, Change in Redemption Value	0
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	(17)	(17)	(14)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture		0
Ending balance	292	274	257
Noncontrolling Interest, Change in Redemption Value	0
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ending balance	53	53	60
Noncontrolling Interest, Change in Redemption Value	0
AMPS Impact on Stockholders Equity		(9)
Treasury Stock, Common
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	3	2	(2)
Ending balance	(17)	(15)	(3)
Noncontrolling Interest, Change in Redemption Value	0
Treasury Stock, Value, Acquired, Cost Method	5	(14)
Parent Company [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income, net of income tax	96	211	(38)
Stock-based compensation	(17)	(17)	(14)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	(5)	(4)	(6)
Stockholders' Equity Attributable to Parent	1,362	1,252	1,038	$ 1,080
Noncontrolling Interest, Change in Redemption Value	5	3
Treasury Stock, Value, Acquired, Cost Method	(5)
Parent Company [Member] \| Accounting Standards Update 2016-13 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Effect of New Accounting Principle			0
Parent Company [Member] \| Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income, net of income tax	4	521	(17)
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	(8)	(5)	(4)
Stockholders' Equity Attributable to Parent	1,246	1,245	726	759
Noncontrolling Interest, Change in Redemption Value	5	3
Parent Company [Member] \| Retained Earnings [Member] \| Accounting Standards Update 2016-13 [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Effect of New Accounting Principle			0
Parent Company [Member] \| AOCI Attributable to Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income, net of income tax	93	(310)	(21)
Stockholders' Equity Attributable to Parent	(160)	(253)	58	79
Parent Company [Member] \| Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent	0	0	0	0
Parent Company [Member] \| Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent	0	0	0	0
Parent Company [Member] \| Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	(17)	(17)	(14)
Stockholders' Equity Attributable to Parent	292	274	257	242
Parent Company [Member] \| Treasury Stock, Common
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation		0
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	3	2	(2)
Stockholders' Equity Attributable to Parent	(17)	$ (15)	$ (3)	$ (1)
Treasury Stock, Value, Acquired, Cost Method	$ (5)

Schedule II - Condensed Finan_4

Schedule II - Condensed Financial Information of Registrant (Parent Company Only) - Condensed Statements of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended			21 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2023
Cash flows from operating activities:
Net income	$ 5	$ 522	$ (16)
Adjustments to reconcile net income loss to net cash used in operating activities:
Accretion (Amortization) of Discounts and Premiums, Investments	(15)	(11)	(13)
Net investment gains (losses), including impairments	22	(31)	(7)
Share-based compensation	17	17	14
Proceeds from Contributions from Affiliates	8	6	6
Other, net	13	(196)	(56)
Net cash provided by operating activities	200	1,335	(131)
Cash flows from investing activities:
Proceeds from matured bonds	74	206	698
Purchases of bonds	(415)	(403)	(343)
Change in short-term investments	118	(52)	98
Proceeds from Sale and Maturity of Other Investments	209	166	39
Payments for (Proceeds from) Other Investing Activities	6	9	(5)
Net cash provided by investing activities	435	866	776
Cash flows from financing activities:
Net Cash Provided by (Used in) Financing Activities	(423)	(2,163)	(657)
Cash and cash equivalents at beginning of period	31	17
Cash and cash equivalents end of period	16	31	17	$ 16
Cash paid during the period for:
Income taxes	11	6	15
Payments to Acquire Businesses, Net of Cash Acquired	7	18	0
Payments for Repurchase of Common Stock	5	14		19
Ambac Financial Group, Inc Parent Company Only [Member]
Cash flows from operating activities:
Net income	4	522	(17)
Adjustments to reconcile net income loss to net cash used in operating activities:
Equity in undistributed net (income) loss of non-debtor subsidiaries	(15)	(542)	1
Accretion (Amortization) of Discounts and Premiums, Investments	0	(7)	(9)
Net investment gains (losses), including impairments	0	14	5
Decrease in current income taxes payable	(2)	(1)	1
Share-based compensation	9	12	14
Decrease in other assets	(5)	41	(5)
Other, net	2	1	(6)
Net cash provided by operating activities	2	46	(10)
Cash flows from investing activities:
Proceeds from matured bonds	0	68	33
Purchases of bonds	(1)	(1)	(34)
Change in short-term investments	20	(51)	105
Proceeds from Sale and Maturity of Other Investments	(3)	(4)	(8)
Net cash provided by investing activities	16	12	95
Capital Contribution to Subsidiaries	(16)	(42)	(92)
Cash flows from financing activities:
Net Cash Provided by (Used in) Financing Activities	(21)	(57)	(92)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect	(2)	1	(6)
Cash and cash equivalents at beginning of period	3	1	7
Cash and cash equivalents end of period	0	3	1	$ 0
Cash paid during the period for:
Income taxes	0	0	$ 0
Payments for Repurchase of Common Stock	$ (5)	$ (14)

Schedule II - Condensed Finan_5

Schedule II - Condensed Financial Information of Registrant (Parent Company Only) Schedule II - Condensed Financial Information of Registrant - Additional Information (Details)	Apr. 29, 1991
Entity Incorporation, Date of Incorporation	Apr. 29, 1991

Schedule II - Condensed Finan_6

Schedule II - Condensed Financial Information of Registrant (Parent Company Only) Schedule II - Condensed Financial Information of Registrant - Income Taxes (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Operating Loss Carryforwards	$ 3,400
AFG [Member]
Operating Loss Carryforwards	1,640
Ambac Assurance [Member]
Operating Loss Carryforwards	$ 1,760
Ambac Assurance [Member] \| Minimum [Member]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2030
Ambac Assurance [Member] \| Maximum [Member]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2042
Interest Expense \| U. S. Federal Net Operating Tax [Member]
Operating Loss Carryforwards	$ 274

SEC Schedule, Article 12-16, Su

SEC Schedule, Article 12-16, Supplementary Insurance Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Liability for Claims and Claims Adjustment Expense	$ 893	$ 805
Deferred Policy Acquisition Cost	11	3
Unearned premiums	422	372
Premiums Earned, Net	78	56	$ 47
Net Investment Income	140	17	139
Policyholder Benefits and Claims Incurred, Net	(33)
Deferred Policy Acquisition Costs, Amortization Expense	11	3	1
General and Administrative Expense	156	141	111
Premiums Written, Net	44	23	(33)
Legacy Financial Guarantee
Liability for Claims and Claims Adjustment Expense	696	715	1,538
Deferred Policy Acquisition Cost	0	0	0
Unearned premiums	267	287	385
Premiums Earned, Net	26	42	46
Net Investment Income	127	12	138
Policyholder Benefits and Claims Incurred, Net	(69)	(406)	(89)
Deferred Policy Acquisition Costs, Amortization Expense	0	0	0
General and Administrative Expense	108	104	77
Premiums Written, Net	(35)	(6)	(35)
Specialty Property & Casualty Program [Domain]
Liability for Claims and Claims Adjustment Expense	197	90	32
Deferred Policy Acquisition Cost	11	3	0
Unearned premiums	155	85	10
Premiums Earned, Net	52	14	1
Net Investment Income	4	2	1
Policyholder Benefits and Claims Incurred, Net	37	9	0
Deferred Policy Acquisition Costs, Amortization Expense	11	3	0
General and Administrative Expense	16	13	9
Premiums Written, Net	$ 80	$ 29	$ 13