Aon (AON) 10-Q26 Jul 242024 Q2 Quarterly reportFinancial data

Company Profile

Cover

Cover - shares	6 Months Ended
Cover - shares	Jun. 30, 2024	Jul. 25, 2024
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2024
Document Transition Report	false
Entity File Number	1-7933
Entity Registrant Name	Aon plc
Entity Incorporation, State or Country Code	L2
Entity Tax Identification Number	98-1539969
Entity Address, Address Line One	Metropolitan Building, James Joyce Street
Entity Address, City or Town	Dublin 1
Entity Address, Country	IE
Entity Address, Postal Zip Code	D01 K0Y8
Country Region	353
City Area Code	1
Local Phone Number	266 6000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		217,242,161
Entity Central Index Key	0000315293
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Class A Ordinary Shares $0.01 nominal value
Entity Information [Line Items]
Title of 12(b) Security	Class A Ordinary Shares $0.01 nominal value
Trading Symbol	AON
Security Exchange Name	NYSE
Guarantees of Aon plc’s 3.875% Senior Notes due 2025
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 3.875% Senior Notes due 2025
Trading Symbol	AON25
Security Exchange Name	NYSE
Guarantees of Aon plc’s 2.875% Senior Notes due 2026
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 2.875% Senior Notes due 2026
Trading Symbol	AON26
Security Exchange Name	NYSE
Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.85% Senior Notes due 2027
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.85% Senior Notes due 2027
Trading Symbol	AON27
Security Exchange Name	NYSE
Guarantees of Aon North America, Inc.’s 5.125% Senior Notes due 2027
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon North America, Inc.’s 5.125% Senior Notes due 2027
Trading Symbol	AON27B
Security Exchange Name	NYSE
Guarantees of Aon North America, Inc.’s 5.150% Senior Notes due 2029
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon North America, Inc.’s 5.150% Senior Notes due 2029
Trading Symbol	AON29
Security Exchange Name	NYSE
Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.05% Senior Notes due 2031
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.05% Senior Notes due 2031
Trading Symbol	AON31
Security Exchange Name	NYSE
Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.60% Senior Notes due 2031
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.60% Senior Notes due 2031
Trading Symbol	AON31A
Security Exchange Name	NYSE
Guarantees of Aon North America, Inc.’s 5.300% Senior Notes due 2031
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon North America, Inc.’s 5.300% Senior Notes due 2031
Trading Symbol	AON31B
Security Exchange Name	NYSE
Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.00% Senior Notes due 2032
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.00% Senior Notes due 2032
Trading Symbol	AON32
Security Exchange Name	NYSE
Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.35% Senior Notes due 2033
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.35% Senior Notes due 2033
Trading Symbol	AON33
Security Exchange Name	NYSE
Guarantees of Aon North America, Inc.’s 5.450% Senior Notes due 2034
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon North America, Inc.’s 5.450% Senior Notes due 2034
Trading Symbol	AON34
Security Exchange Name	NYSE
Guarantees of Aon plc’s 4.25% Senior Notes due 2042
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 4.25% Senior Notes due 2042
Trading Symbol	AON42
Security Exchange Name	NYSE
Guarantees of Aon plc’s 4.45% Senior Notes due 2043
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 4.45% Senior Notes due 2043
Trading Symbol	AON43
Security Exchange Name	NYSE
Guarantees of Aon plc’s 4.60% Senior Notes due 2044
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 4.60% Senior Notes due 2044
Trading Symbol	AON44
Security Exchange Name	NYSE
Guarantees of Aon plc’s 4.75% Senior Notes due 2045
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon plc’s 4.75% Senior Notes due 2045
Trading Symbol	AON45
Security Exchange Name	NYSE
Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.90% Senior Notes due 2051
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.90% Senior Notes due 2051
Trading Symbol	AON51
Security Exchange Name	NYSE
Guarantees of Aon Corporation and Aon Global Holdings plc’s 3.90% Senior Notes due 2052
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon Corporation and Aon Global Holdings plc’s 3.90% Senior Notes due 2052
Trading Symbol	AON52
Security Exchange Name	NYSE
Guarantees of Aon North America, Inc.’s 5.750% Senior Notes due 2054
Entity Information [Line Items]
Title of 12(b) Security	Guarantees of Aon North America, Inc.’s 5.750% Senior Notes due 2054
Trading Symbol	AON54
Security Exchange Name	NYSE

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenue
Total revenue	$ 3,760	$ 3,177	$ 7,830	$ 7,048
Expenses
Compensation and benefits	2,130	1,754	4,013	3,546
Information technology	132	129	256	268
Premises	82	68	153	143
Depreciation of fixed assets	45	39	89	77
Amortization and impairment of intangible assets	128	25	144	50
Other general expense	455	320	803	649
Accelerating Aon United Program expenses	132	0	251	0
Total operating expenses	3,104	2,335	5,709	4,733
Operating income	656	842	2,121	2,315
Interest income	31	5	59	10
Interest expense	(225)	(130)	(369)	(241)
Other income (expense)	236	(59)	311	(84)
Income before income taxes	698	658	2,122	2,000
Income tax expense	160	83	491	346
Net income	538	575	1,631	1,654
Less: Net income attributable to redeemable and non-redeemable noncontrolling interests	14	15	36	44
Net income attributable to Aon shareholders	$ 524	$ 560	$ 1,595	$ 1,610
Basic net income per share attributable to Aon shareholders (in dollars per share)	$ 2.47	$ 2.74	$ 7.75	$ 7.84
Diluted net income per share attributable to Aon shareholders (in dollars per share)	$ 2.46	$ 2.71	$ 7.72	$ 7.79
Weighted average ordinary shares outstanding - basic (in shares)	212.5	204.7	205.8	205.4
Weighted average ordinary shares outstanding - diluted (in shares)	213.3	206.3	206.7	206.7

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 538	$ 575	$ 1,631	$ 1,654
Less: Net income attributable to redeemable and non-redeemable noncontrolling interests	14	15	36	44
Net income attributable to Aon shareholders	524	560	1,595	1,610
Other comprehensive income, net of tax:
Change in fair value of financial instruments	1	8	76	11
Foreign currency translation adjustments	(88)	174	(220)	228
Postretirement benefit obligation	13	24	39	46
Total other comprehensive income (loss)	(74)	206	(105)	285
Less: Other comprehensive income attributable to noncontrolling interests	0	0	0	0
Total other comprehensive income (loss) attributable to Aon shareholders	(74)	206	(105)	285
Comprehensive income attributable to Aon shareholders	$ 450	$ 766	$ 1,490	$ 1,895

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Financial Position - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Current assets
Cash and cash equivalents	$ 974	$ 778
Short-term investments	182	369
Receivables, net	4,459	3,254
Fiduciary assets	18,865	16,307
Other current assets	1,063	996
Total current assets	25,543	21,704
Goodwill	15,281	8,414
Intangible assets, net	6,794	234
Fixed assets, net	636	638
Operating lease right-of-use assets	723	650
Deferred tax assets	1,218	1,195
Prepaid pension	629	618
Other non-current assets	629	506
Total assets	51,453	33,959
Current liabilities
Accounts payable and accrued liabilities	2,319	2,262
Short-term debt and current portion of long-term debt	4	1,204
Fiduciary liabilities	18,865	16,307
Other current liabilities	2,310	1,878
Total current liabilities	23,498	21,651
Long-term debt	17,610	9,995
Non-current operating lease liabilities	702	641
Deferred tax liabilities	1,177	115
Pension, other postretirement, and postemployment liabilities	1,173	1,225
Other non-current liabilities	1,135	1,074
Total liabilities	45,295	34,701
Redeemable noncontrolling interests	130	0
Equity (deficit)
Ordinary shares - $0.01 nominal value Authorized: 500.0 shares (issued: 2024 - 217.2; 2023 - 198.6)	2	2
Additional paid-in capital	12,910	6,944
Accumulated deficit	(2,574)	(3,399)
Accumulated other comprehensive loss	(4,478)	(4,373)
Total Aon shareholders' equity (deficit)	5,860	(826)
Nonredeemable noncontrolling interests	168	84
Total equity (deficit)	6,028	(742)
Total liabilities, redeemable noncontrolling interests and equity (deficit)	$ 51,453	$ 33,959

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Financial Position (Parenthetical) - $ / shares	Jun. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Ordinary shares, nominal value (in dollars per share)	$ 0.01	$ 0.01
Ordinary shares, authorized shares (in shares)	500,000,000	500,000,000
Ordinary shares, issued shares (in shares)	217,200,000	198,600,000

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Shareholders’ Equity (Deficit) (Unaudited) - USD ($) shares in Millions, $ in Millions		Total	Ordinary Shares and Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss, Net of Tax	Non- redeemable Non- controlling Interests
Beginning balance (in shares) at Dec. 31, 2022			205.4
Beginning balance at Dec. 31, 2022		$ (429)	$ 6,866	$ (2,772)	$ (4,623)	$ 100
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		1,079		1,050		29
Shares issued - employee stock compensation plans (in shares)			0.9
Shares issued - employee stock compensation plans		(132)	$ (131)	(1)
Shares repurchased (in shares)			(1.8)
Shares repurchased		(550)		(550)
Share-based compensation expense		127	$ 127
Dividends to shareholders		(115)		(115)
Net change in fair value of financial instruments		3			3
Net foreign currency translation adjustments		54			54
Net postretirement benefit obligation		22			22
Dividends paid to nonredeemable noncontrolling interests on subsidiary common stock		(1)				(1)
Ending balance (in shares) at Mar. 31, 2023			204.5
Ending balance at Mar. 31, 2023		58	$ 6,862	(2,388)	(4,544)	128
Beginning balance (in shares) at Dec. 31, 2022			205.4
Beginning balance at Dec. 31, 2022		(429)	$ 6,866	(2,772)	(4,623)	100
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		1,654
Net change in fair value of financial instruments		11
Net foreign currency translation adjustments		228
Net postretirement benefit obligation		46
Ending balance (in shares) at Jun. 30, 2023			203.2
Ending balance at Jun. 30, 2023		162	$ 6,908	(2,505)	(4,338)	97
Beginning balance (in shares) at Mar. 31, 2023			204.5
Beginning balance at Mar. 31, 2023		58	$ 6,862	(2,388)	(4,544)	128
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		575		560		15
Shares issued - employee stock compensation plans (in shares)			0.4
Shares issued - employee stock compensation plans		(52)	$ (52)
Shares repurchased (in shares)			(1.7)
Shares repurchased		(550)		(550)
Share-based compensation expense		99	$ 99
Dividends to shareholders		(127)		(127)
Net change in fair value of financial instruments		8			8
Net foreign currency translation adjustments		174			174
Net postretirement benefit obligation		24			24
Purchases of subsidiary shares from nonredeemable noncontrolling interests		(2)	$ (1)			(1)
Dividends paid to nonredeemable noncontrolling interests on subsidiary common stock		(45)				(45)
Ending balance (in shares) at Jun. 30, 2023			203.2
Ending balance at Jun. 30, 2023		$ 162	$ 6,908	(2,505)	(4,338)	97
Beginning balance (in shares) at Dec. 31, 2023		198.6	198.6
Beginning balance at Dec. 31, 2023		$ (742)	$ 6,946	(3,399)	(4,373)	84
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		1,093		1,071		22
Shares issued - employee stock compensation plans (in shares)			0.8
Shares issued - employee stock compensation plans		(104)	$ (104)
Shares repurchased (in shares)			(0.8)
Shares repurchased		(250)		(250)
Share-based compensation expense		130	$ 130
Dividends to shareholders		(122)		(122)
Net change in fair value of financial instruments		75			75
Net foreign currency translation adjustments		(132)			(132)
Net postretirement benefit obligation		26			26
Purchases of subsidiary shares from nonredeemable noncontrolling interests		(1)	$ (1)
Dividends paid to nonredeemable noncontrolling interests on subsidiary common stock		(1)				(1)
Ending balance (in shares) at Mar. 31, 2024			198.6
Ending balance at Mar. 31, 2024		$ (28)	$ 6,971	(2,700)	(4,404)	105
Beginning balance (in shares) at Dec. 31, 2023		198.6	198.6
Beginning balance at Dec. 31, 2023		$ (742)	$ 6,946	(3,399)	(4,373)	84
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		1,631
Net change in fair value of financial instruments		76
Net foreign currency translation adjustments		(220)
Net postretirement benefit obligation		$ 39
Ending balance (in shares) at Jun. 30, 2024		217.2	217.2
Ending balance at Jun. 30, 2024		$ 6,028	$ 12,912	(2,574)	(4,478)	168
Beginning balance (in shares) at Mar. 31, 2024			198.6
Beginning balance at Mar. 31, 2024		(28)	$ 6,971	(2,700)	(4,404)	105
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		538
Net income	[1]	536		524		12
Shares issued - NFP Transaction (in shares)			19
Shares issued - NFP Transaction		5,882	$ 5,882
Shares issued - employee stock compensation plans (in shares)			0.4
Shares issued - employee stock compensation plans		(45)	$ (45)
Shares repurchased (in shares)			(0.8)
Shares repurchased		(250)		(250)
Share-based compensation expense		117	$ 117
Dividends to shareholders		(148)		(148)
Net change in fair value of financial instruments		1			1
Net foreign currency translation adjustments		(88)			(88)
Net postretirement benefit obligation		13			13
Purchases of subsidiary shares from nonredeemable noncontrolling interests		86				86
Dividends paid to nonredeemable noncontrolling interests on subsidiary common stock		(35)				(35)
Adjustments to redeemable noncontrolling interests		$ (13)	$ (13)
Ending balance (in shares) at Jun. 30, 2024		217.2	217.2
Ending balance at Jun. 30, 2024		$ 6,028	$ 12,912	$ (2,574)	$ (4,478)	$ 168

[1] The Company’s Net income totaled $538 million for the quarter ended June 30, 2024, which included $2 million of Net income related to redeemable noncontrolling interests.

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Shareholders’ Equity (Deficit) (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024
Statement of Stockholders' Equity [Abstract]
Dividends (in dollars per share)	$ 0.675	$ 0.615	$ 0.615	$ 0.56
Net income	$ 538	$ 1,093	$ 575	$ 1,079	$ 1,631
Net income related to redeemable noncontrolling interest					$ 2

Condensed Consolidated Statem_7

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash flows from operating activities
Net income	$ 1,631	$ 1,654
Adjustments to reconcile net income to cash provided by operating activities:
Gain from sales of businesses	(257)	0
Depreciation of fixed assets	89	77
Amortization and impairment of intangible assets	144	50
Share-based compensation expense	247	226
Deferred income taxes	(122)	(168)
Other, net	(112)	28
Change in assets and liabilities:
Receivables, net	(959)	(704)
Accounts payable and accrued liabilities	(251)	(515)
Accelerating Aon United Program liabilities	61	0
Current income taxes	60	53
Pension, other postretirement and postemployment liabilities	(17)	(3)
Other assets and liabilities	308	433
Cash provided by operating activities	822	1,131
Cash flows from investing activities
Proceeds from investments	146	54
Purchases of investments	(91)	(29)
Net sales of short-term investments - non fiduciary	189	255
Acquisition of businesses, net of cash and funds held on behalf of clients	(2,780)	(8)
Sale of businesses, net of cash and funds held on behalf of clients	352	1
Capital expenditures	(101)	(145)
Cash provided by (used for) investing activities	(2,285)	128
Cash flows from financing activities
Share repurchase	(500)	(1,100)
Proceeds from issuance of shares	27	33
Cash paid for employee taxes on withholding shares	(176)	(216)
Commercial paper issuances, net of repayments	(591)	(217)
Issuance of debt	7,926	744
Repayment of debt	(4,328)	0
Increase in fiduciary liabilities, net of fiduciary receivables	283	999
Cash dividends to shareholders	(269)	(241)
Redeemable and non-redeemable noncontrolling interests, and other financing activities	(108)	(41)
Cash provided by (used for) financing activities	2,264	(39)
Effect of exchange rates on cash and cash equivalents and funds held on behalf of clients	(202)	203
Net increase in cash and cash equivalents and funds held on behalf of clients	599	1,423
Cash, cash equivalents and funds held on behalf of clients at beginning of period	7,722	7,076
Cash, cash equivalents and funds held on behalf of clients at end of period	8,321	8,499
Reconciliation of cash and cash equivalents and funds held on behalf of clients:
Cash and cash equivalents	974	952
Cash and cash equivalents and funds held on behalf of clients classified as held for sale	38	9
Funds held on behalf of clients	7,309	7,538
Total cash and cash equivalents and funds held on behalf of clients	8,321	8,499
Supplemental disclosures:
Interest paid	256	220
Income taxes paid, net of refunds	$ 553	$ 461

Basis of Presentation

Basis of Presentation	6 Months Ended
Basis of Presentation	Jun. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying Condensed Consolidated Financial Statements and Notes thereto have been prepared in accordance with U.S. GAAP. The Condensed Consolidated Financial Statements include the accounts of Aon plc and all of its controlled subsidiaries (“Aon” or the “Company”). Intercompany accounts and transactions have been eliminated. The Condensed Consolidated Financial Statements include, in the opinion of management, all adjustments (consisting of normal recurring adjustments and reclassifications) necessary to present fairly the Company’s consolidated financial position, results of operations, and cash flows for all periods presented. Certain information and disclosures normally included in the Consolidated Financial Statements prepared in accordance with U.S. GAAP have been condensed or omitted. The Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements and Notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. The results for the three and six months ended June 30, 2024 are not necessarily indicative of operating results that may be expected for the full year ending December 31, 2024. Use of Estimates The preparation of the accompanying Condensed Consolidated Financial Statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosures of contingent assets and liabilities at the date of the Condensed Consolidated Financial Statements, and the reported amounts of reserves and expenses. These estimates and assumptions are based on management’s best estimates and judgments. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment. Management believes its estimates to be reasonable given the current facts available. Aon adjusts such estimates and assumptions when facts and circumstances dictate. Illiquid credit markets, volatile equity markets, and foreign currency exchange rate movements increase the uncertainty inherent in such estimates and assumptions. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Changes in estimates resulting from continuing changes in the economic environment would, if applicable, be reflected in the Condensed Consolidated Financial Statements in future periods.

Accounting Principles and Pract

Accounting Principles and Practices	6 Months Ended
Accounting Principles and Practices	Jun. 30, 2024
Accounting Policies [Abstract]
Accounting Principles and Practices	Accounting Principles and Practices We have not made any changes in our significant accounting policies from those disclosed in our Annual Report on Form 10-K for the year ended December 31, 2023 filed with the SEC, except for those described below, which have been added in connection with the acquisition of NFP. Summary of Significant Accounting Principles and Practices Contingent Consideration Contingent consideration may be paid to the former owners of the business and typically will involve the acquired entity reaching specific financial results over a designated period. Contingent consideration payables are recorded at fair value and are included in the purchase price consideration at the time of the acquisition. Subsequent changes in the fair value of contingent consideration obligations are recorded in the Condensed Consolidated Statements of Income. The fair value of contingent consideration payables is based on the expected future payments to be made to the sellers of the acquired businesses in accordance with the provisions outlined in the respective purchase agreements. In determining fair value of the contingent consideration, the acquired business’s future performance is estimated using financial projections for the acquired business and measured against performance targets specified in each purchase agreement. Contingent consideration liabilities are classified as Level 3 because of the Company’s reliance on unobservable inputs. Principles of Consolidations The accompanying Condensed Consolidated Financial Statements include the accounts of Aon plc and those entities in which the Company has a controlling financial interest. To determine if Aon holds a controlling financial interest in an entity, the Company first evaluates if it is required to apply the variable interest model to the entity, otherwise, the entity is evaluated under the voting interest model. When Aon holds rights that give it the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance, combined with a variable interest that gives the right to receive potentially significant benefits or the obligation to absorb potentially significant losses, the Company has a controlling financial interest in that VIE. If the Company is the primary beneficiary of a VIE, the Company consolidates the entity and reflects any relevant noncontrolling interest of other beneficiaries of that entity on the Statement of Consolidated Financial Position. Aon’s interest in VIEs as of June 30, 2024 predominantly relates to assets and liabilities acquired through the acquisition of NFP and are subject to purchase accounting adjustments. Total assets related to consolidated VIEs are approximately 1% of the Company’s Total assets on the Condensed Consolidated Statements of Financial Position for the period ended June 30, 2024. Aon holds a controlling financial interest in entities that are not VIEs when it, directly or indirectly holds more than 50% of the voting rights and the noncontrolling interest holders do not hold substantive participating rights. Redeemable Noncontrolling Interests Redeemable noncontrolling interests represent interests for certain consolidated entities which are subject to redemption rights held by the noncontrolling interests owners outside of the Company’s control at fixed or determinable prices and dates. The interests are initially recorded at fair value and in subsequent reporting periods are adjusted to the estimated redemption value. The adjustments to the redemption value are recorded to additional paid-in capital or retained earnings, when appropriate, on the Condensed Consolidated Statements of Financial Position. The Redeemable noncontrolling interests are considered temporary equity and reported outside of permanent equity on the Condensed Consolidated Statements of Financial Position. The interests are recorded at the greater of the carrying amount adjusted for the noncontrolling interest’s share of net income (loss) and distributions or its redemption value. New Accounting Pronouncements Accounting Standards Issued But Not Yet Adopted Improvements to Reportable Segment Disclosures In November 2023, the FASB issued new accounting guidance, requiring new segment disclosures under ASC 280, Segment Reporting, including disclosure of significant segment expense categories and amounts that are regularly reported to the CODM and included in the segment’s profit or loss. Additionally, all disclosure requirements under ASC 280, including new requirements under this new guidance, will be required on an interim basis. The new guidance is effective for Aon for the year ended December 31, 2024 and interim periods thereafter, with early adoption permitted. An entity will apply the new guidance on a retrospective basis for all periods presented. The Company is currently evaluating the impact the guidance will have on the Notes to Consolidated Financial Statements. Improvements to Income Tax Disclosures In December 2023, the FASB issued new accounting guidance under ASC 740, Income Taxes, which requires additional income tax disclosures on an annual basis, including disaggregation of information presented within the reconciliation of the expected tax to the reported tax by specific categories, with certain reconciling items 5% or greater broken out by nature and/or jurisdiction. The new guidance also requires disclosure of income taxes paid, net of refunds, broken out by federal, state/local, and foreign, including disclosure of individual jurisdictions when greater than 5% of total net income taxes paid. The new guidance is effective for Aon for the year ended December 31, 2025, with early adoption permitted. The Company is evaluating the period of adoption and transition approach, as well as the impact the disclosures will have on the Notes to Consolidated Financial Statements. Securities and Exchange Commission Final Rules The Enhancement and Standardization of Climate-Related Disclosures for Investors In March 2024, the SEC adopted final rules to enhance and standardize climate-related disclosures. The final rules will require the Company to provide certain climate-related information in Item 7, Management’s Discussion and Analysis regarding material climate-related risks, activities to mitigate or adapt to such risks, information regarding oversight and management of climate-related risks, information on climate-related targets or goals, and disclosure of Scope 1 and 2 GHG emissions. Additionally, within the Notes to Consolidated Financial Statements, the Company will be required to disclose the financial statement effects of severe weather events and other natural conditions. The final rules are effective for Aon for the year ended December 31, 2025, with the exception of GHG emissions disclosures which are effective for Aon for the year ended December 31, 2026. After the adoption of the final rules, the final rules became subject to several legal challenges, and on April 4, 2024 the SEC voluntarily stayed the final rules pending judicial review. The Company is currently evaluating the impact that the guidance will have on our disclosures and will monitor the judicial process for impacts on the disclosure requirements.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	6 Months Ended
Revenue from Contracts with Customers	Jun. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	Revenue from Contracts with Customers Disaggregation of Revenue The following table summarizes revenue from contracts with customers by principal service line (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Commercial Risk Solutions $ 2,015 $ 1,774 $ 3,823 $ 3,552 Reinsurance Solutions 635 607 1,802 1,684 Health Solutions 662 447 1,395 1,118 Wealth Solutions 463 352 833 702 Eliminations (15) (3) (23) (8) Total revenue $ 3,760 $ 3,177 $ 7,830 $ 7,048 Consolidated revenue from contracts with customers by geographic area, which is attributed on the basis of where the services are performed, is as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 United States $ 1,837 $ 1,427 $ 3,349 $ 2,922 Americas other than United States 362 308 685 609 United Kingdom 548 506 1,131 1,060 Ireland 35 28 68 58 Europe, Middle East, & Africa other than United Kingdom and Ireland 566 512 1,775 1,614 Asia Pacific 412 396 822 785 Total revenue $ 3,760 $ 3,177 $ 7,830 $ 7,048 Contract Costs An analysis of the changes in the net carrying amount of costs to fulfill contracts with customers are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Balance at beginning of period $ 269 $ 257 $ 370 $ 355 Additions 386 355 766 717 Amortization (390) (373) (868) (835) Impairment — — — — Foreign currency translation and other (1) 3 (4) 5 Balance at end of period $ 264 $ 242 $ 264 $ 242 An analysis of the changes in the net carrying amount of costs to obtain contracts with customers are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Balance at beginning of period $ 194 $ 183 $ 195 $ 185 Additions 18 13 32 23 Amortization (14) (13) (27) (25) Impairment — — — — Foreign currency translation and other (2) 3 (4) 3 Balance at end of period $ 196 $ 186 $ 196 $ 186

Accelerating Aon United Program

Accelerating Aon United Program	6 Months Ended
Accelerating Aon United Program	Jun. 30, 2024
Restructuring and Related Activities [Abstract]
Accelerating Aon United Program	Accelerating Aon United Program In the third quarter of 2023, Aon initiated a three-year restructuring program called the Accelerating Aon United Program (the “Program”) with the purpose of streamlining the Company’s technology infrastructure, optimizing its leadership structure and resource alignment, and reducing its real estate footprint to align to its hybrid working strategy. The Program includes technology-related costs to facilitate streamlining and simplifying operations, headcount reduction costs, and costs associated with asset impairments, including real estate consolidation and technology costs. Program charges are recognized within Accelerating Aon United Program expenses on the accompanying Condensed Consolidated Statements of Income and consists of the following cost activities: • Technology and other – includes costs associated with actions taken to rationalize certain applications and to optimize technology across the Company. These costs may include contract termination fees and other non-capitalizable costs associated with Program initiatives, which include professional service fees. • Workforce optimization – includes costs associated with headcount reduction and other separation-related costs. • Asset impairments – includes non-cash costs associated with impairment of assets, as they are identified, including ROU lease assets, leasehold improvements, and other capitalized assets no longer providing economic benefit. The Program is currently expected to result in cumulative costs of approximately $1.0 billion, consisting of approximately $900 million of cash charges and approximately $100 million of non-cash charges. For the three and six months ended June 30, 2024, total Program costs incurred were $132 million and $251 million, respectively. The Company expects to continue to review the implementation of elements of the Program throughout the course of the Program and, therefore, there may be changes to expected timing, estimates of expected costs, and related savings. The Company’s unpaid liabilities for charges under the Program are generally included in Accounts payable and accrued liabilities in the Condensed Consolidated Statements of Financial Position. The changes in the Company’s liabilities for the Program as of June 30, 2024 are as follows (in millions): Technology and other Workforce optimization Asset impairments Total Liability balance as of January 1, 2024 $ 14 $ 86 $ — $ 100 Charges 51 145 55 251 Cash payments (29) (69) — (98) Foreign currency translation and other — (3) — (3) Non-cash charges (1) (27) (10) (55) (92) Liability balance as of June 30, 2024 $ 9 $ 149 $ — $ 158 Total costs incurred from inception to date $ 65 $ 248 $ 73 $ 386 (1)

Cash and Cash Equivalents and S

Cash and Cash Equivalents and Short-Term Investments	6 Months Ended
Cash and Cash Equivalents and Short-Term Investments	Jun. 30, 2024
Cash, Cash Equivalents, and Short-Term Investments [Abstract]
Cash and Cash Equivalents and Short-Term Investments	Cash and Cash Equivalents and Short-Term Investments Cash and cash equivalents include cash balances and all highly liquid instruments with initial maturities of three months or less. Short-term investments consist of money market funds. The estimated fair value of Cash and cash equivalents and Short-term investments approximates their carrying values. At June 30, 2024, Cash and cash equivalents and Short-term investments were $1.2 billion compared to $1.1 billion at December 31, 2023. Of the total balances, $116 million and $120 million were restricted as to their use at June 30, 2024 and December 31, 2023, respectively. Included within Short-term investments as of June 30, 2024 and December 31, 2023, were £55 million ( $69 million at June 30, 2024 exchange rates) and £63 million ($80 million at December 31, 2023 exchange rates), respectively, of operating funds required to be held by the Company in the U.K. by the FCA, a U.K.-based regulator.

Other Financial Data

Other Financial Data	6 Months Ended
Other Financial Data	Jun. 30, 2024
Other Financial Data [Abstract]
Other Financial Data	Other Financial Data Condensed Consolidated Statements of Income Information Other Income (Expense) Other income (expense) consists of the following (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Gain from sales of businesses $ 257 $ — $ 257 $ — Foreign currency remeasurement 5 (37) 9 (56) Equity earnings 1 (1) 3 2 Pension and other postretirement (11) (43) (21) (60) Extinguishment of debt (6) — (6) — Financial instruments and other (1) (10) 22 69 30 Total $ 236 $ (59) $ 311 $ (84) (1) In first quarter of 2024, an $82 million gain was recognized related to deferred consideration from the affiliates of The Blackstone Group L.P. and the other designated purchasers related to a divestiture completed in a prior year period. Refer to Note 7 “Acquisitions and Dispositions of Businesses” for additional information. Condensed Consolidated Statements of Financial Position Information Allowance for Doubtful Accounts Changes in the net carrying amount of allowance for doubtful accounts are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Balance at beginning of period $ 81 $ 83 $ 79 $ 76 Provision 6 2 11 9 Accounts written off, net of recoveries — (3) (2) (3) Foreign currency translation and other — 1 (1) 1 Balance at end of period $ 87 $ 83 $ 87 $ 83 Other Current Assets The components of Other current assets are as follows (in millions): As of June 30, December 31, Assets held for sale (1) $ 359 $ 354 Costs to fulfill contracts with customers (2) 264 370 Prepaid expenses 176 100 Taxes receivable 37 35 Other 227 137 Total $ 1,063 $ 996 (1) Refer to Note 7 “Acquisitions and Dispositions of Businesses” for further information. (2) Refer to Note 3 “Revenue from Contracts with Customers” for further information. Other Non-Current Assets The components of Other non-current assets are as follows (in millions): As of June 30, December 31, Costs to obtain contracts with customers (1) $ 196 $ 195 Taxes receivable 92 100 Investments 83 45 Leases 17 26 Other 241 140 Total $ 629 $ 506 (1) Refer to Note 3 “Revenue from Contracts with Customers” for further information. Other Current Liabilities The components of Other current liabilities are as follows (in millions): As of June 30, December 31, Deferred revenue (1) $ 391 $ 270 Taxes payable 337 291 Leases 203 182 Contingent consideration 106 — Liabilities held for sale (2) 64 69 Other 1,209 1,066 Total $ 2,310 $ 1,878 (1) During the three and six months ended June 30, 2024, revenue of $199 million and $378 million, respectively, was recognized in the Condensed Consolidated Statements of Income. During the three and six months ended June 30, 2023, revenue of $169 million and $336 million, respectively, was recognized in the Condensed Consolidated Statements of Income. (2) Refer to Note 7 “Acquisitions and Dispositions of Businesses” for further information. Other Non-Current Liabilities The components of Other non-current liabilities are as follows (in millions): As of June 30, December 31, Taxes payable (1) $ 848 $ 827 Contingent consideration 91 — Compensation and benefits 59 59 Deferred revenue 34 33 Leases — 10 Other 103 145 Total $ 1,135 $ 1,074 (1) Includes $72 million for the non-current portion of the one-time mandatory transition tax on accumulated foreign earnings as of December 31, 2023.

Acquisitions and Dispositions o

Acquisitions and Dispositions of Businesses	6 Months Ended
Acquisitions and Dispositions of Businesses	Jun. 30, 2024
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
Acquisitions and Dispositions of Businesses	Acquisitions and Dispositions of Businesses Completed Acquisitions The Company completed eight acquisitions d uring the three and six months ended June 30, 2024 and one acquisition during the three and six months ended June 30, 2023. On April 25, 2024 (the “Acquisition Date”), the Company completed the acquisition of NFP (the “NFP Transaction”), a leading middle market property and casualty broker, benefits consultant, wealth manager, and retirement plan advisor, with more than 7,700 colleagues. The Transaction expands Aon’s presence in the large and fast-growing middle-market and enhances NFP’s strong existing client relationships and distribution, by bringing Aon’s data and analytics-based content, capabilities, and expertise, delivered through the Aon Business Services platform. 2024 Acquisitions On June 18, 2024, the Company completed the acquisition of 100% of the share capital of Southern Insurance Agency, L.L.C., a U.S.-based insurance and financial services business. On June 13, 2024, the Company completed the acquisition of 100% of the share capital of Sean Barrett Bloodstock Insurance Limited, an Ireland-based insurance brokerage. On May 31, 2024, the Company completed the acquisition of 100% of the share capital of Walden Wealth Partners LLC., a U.S.-based registered investment advisor firm. On May 31, 2024, the Company completed the acquisition of 100% of the share capital of the Morley Agency, Inc., a U.S.-based commercial and person lines P&C insurance broker. On May 2, 2024, the Company completed the acquisition of 100% of the share capital of Honest Employment Law Practice Ltd., a U.K.-based business that provides consulting and outsourcing services. On April 26, 2024, the Company completed the acquisition of 100% of the share capital of NOVABROK Correduría de Seguros, S.L., a Spain-based insurance broker. On April 25, 2024, the Company completed the acquisition of 100% of the share capital of NFP Intermediate Holdings A Corp. (“NFP”), a leading middle market property and casualty broker, benefits consultant, wealth manager, and retirement plan advisor. On April 3, 2024, the Company completed the acquisition of 100% of the share capital of Global Insurance Brokers Private Limited, an India-based broker that delivers risk management, insurance, and reinsurance broking services. Acquisition of NFP The Company acquired 100% of the outstanding equity interests of NFP Intermediate Holdings A Corp. in a cash-and-stock merger for an aggregate preliminary purchase price totaling $9.1 billion, including approximately $3.2 billion used to settle indebtedness of NFP and cash consideration to the selling shareholders, and approximately 19 million class A ordinary shares with a fair value of approximately $5.9 billion, based on the Company’s closing stock price on April 25, 2024. As part of the NFP Transaction, the Company acquired certain less-than-wholly owned entities, resulting in the recognition of noncontrolling interests which are described further below. The Company financed the NFP Transaction, in part, with the net proceeds from Senior Notes issued on March 1, 2024 totaling to an aggregate amount of $6.0 billion and proceeds from a $2.0 billion delayed draw term loan which was drawn on April 25, 2024. Refer to Note 9 “Debt” for further information. Aon accounted for the NFP Transaction as a business combination under the acquisition method of accounting. The acquisition method requires the Company to measure identifiable assets acquired and liabilities assumed at their fair values as of the Acquisition Date, with the excess of the consideration transferred over those fair values recorded as goodwill. Determining the fair value of intangible assets acquired requires significant judgements, assumptions, and estimates about future events, which the Company believes are reasonable. Use of different estimates and judgements could produce materially different results. The preliminary fair values of consideration transferred, assets acquired, liabilities assumed, and redeemable and nonredeemable noncontrolling interests are subject to adjustment when purchase accounting is finalized. The following table includes these amounts recognized as a result of the Company’s acquisitions (in millions): Six months ended June 30, 2024 NFP Acquisition Other Acquisitions Total Consideration transferred: Cash $ 3,247 $ 109 $ 3,356 Deferred and contingent consideration — 7 7 Class A ordinary shares issued 5,882 — 5,882 Aggregate consideration transferred $ 9,129 $ 116 $ 9,245 Assets acquired: Cash and cash equivalents $ 293 $ 3 $ 296 Receivables 321 3 324 Fiduciary assets (1) 411 6 417 Goodwill 6,953 69 7,022 Other intangible assets: Customer-related and contract-based 5,825 50 5,875 Tradenames 800 — 800 Technology and other 25 1 26 Operating lease right-of-use assets 143 2 145 Current assets 110 3 113 Non-current assets 169 1 170 Total assets acquired 15,050 138 15,188 Liabilities assumed: Accounts payable and accrued liabilities $ 283 $ 8 $ 291 Fiduciary liabilities 411 6 417 Current liabilities 227 — 227 Long-term debt 3,422 — 3,422 Non-current operating lease liabilities 125 2 127 Deferred tax liabilities 1,123 6 1,129 Non-current liabilities 142 — 142 Total liabilities assumed 5,733 22 5,755 Less: Fair value of redeemable noncontrolling interests (103) — (103) Less: Fair value of nonredeemable noncontrolling interests (85) — (85) Net assets acquired $ 9,129 $ 116 $ 9,245 (1) Includes $283 million of funds held on behalf of clients. The purchase price related to the NFP Transaction exceeded the estimated fair value of the tangible and identifiable intangible assets acquired and liabilities assumed and, as a result of the purchase allocation, the Company recorded goodwill of approximately $7.0 billion, which is fully allocated to the Aon United segment and is not deductible for tax purposes. The goodwill recognized is attributable primarily to anticipated growth opportunities and synergies as a result of the NFP Transaction which provides the Company with an expanded presence in the large and fast-growing middle-market. The fair value of the tangible assets and liabilities acquired in the NFP Transaction approximated their carrying values as of the Acquisition Date. The Company used independent third-party valuation specialists to assist in determining the fair value of certain intangible assets acquired and liabilities assumed. Provisional estimates of fair value are established at the time of the NFP Transaction. Such estimates are preliminary in nature and, therefore, could be subject to material adjustments. Any necessary adjustments must be finalized within one year of the Acquisition Date. There are significant estimates used in determining the fair values of certain intangible assets acquired, which consist of customer-related and contract-based assets, tradename, and technology, as well as certain liabilities assumed, which consist of contingent consideration obligations. • Customer-related and contract-based assets: The fair value was estimated based on a multi-period excess earnings method of the income approach and used estimated financial projections developed by management applying market participant assumptions. The customer relationships are amortized over 20 years based upon the estimated economic benefits received. • Tradename: The fair value was estimated based on a relief from royalty method of the income approach, considering publicly available third-party trade name royalty rates as well as expected revenue generated by the use of the tradename over its anticipated life. The trade name is amortized over 10 years based upon the estimated economic benefits received. • Technology: The fair value was estimated based on a replacement cost method of the cost approach which estimates the cost the Company would incur in rebuilding the technology. The technology is amortized over 7 years based upon the estimated economic benefits received. • Contingent Consideration: The fair value of assumed contingent consideration was estimated based on a Monte Carlo simulation in a risk-neutral framework. Key assumptions for estimating fair value include projected revenue or EBITDA, as well as the discount rate and volatility associated with the relevant metric. Contingent consideration liabilities are classified as Level 3 because of the Company’s reliance on unobservable inputs. The estimates described above directly impact the amount of identified intangible assets recognized and the related amortization expense in future periods as well as certain liabilities assumed. Intangible assets acquired had a weighted average useful economic life of 19 years. As of June 30, 2024, the aggregate intangible assets relating to the NFP Transaction of approximately $6.5 billion were recorded in Intangible assets, net on the Condensed Consolidated Balance Sheets. These amounts are considered preliminary and, therefore, the Company may refine estimates and adjust the assets acquired and liabilities assumed over a measurement period, not to exceed one year from the Acquisition Date. These adjustments are made in the period in which the amounts are determined, and the current period income effect of such adjustments will be calculated as if the adjustments had been completed as of the Acquisition Date. For the three and six months ended June 30, 2024, the Company recognized $79 million and $90 million, respectively, of transaction costs in Other general expenses. Additional transaction costs include $6 million of debt extinguishment charges recognized in Other income (expense) for the three and six months ended June 30, 2024 in connection with the extinguishment of assumed long-term debt through cash tender offers on April 26, 2024. The Company’s Condensed Consolidated Financial Statements for the three and six months ended June 30, 2024 include the operations of NFP from the Acquisition Date. The following table presents the NFP revenue and earnings as reported in the Company’s Condensed Consolidated Statements of Income (in millions): Three Months Ended June 30, 2024 Revenue $ 442 Net loss attributable to Aon shareholders $ (19) Supplemental Pro Forma Combined Information (Unaudited) The following unaudited pro forma combined financial information presents the combined results of operations of the Company as if the NFP Transaction occurred on January 1, 2023. The unaudited pro forma financial information is presented for informational purposes only and is not indicative of the results of operations that would have been achieved if the NFP Transaction had taken place on the date indicated or of results that may occur in the future (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Revenue $ 3,910 $ 3,729 $ 8,528 $ 8,099 Net income attributable to Aon shareholders 465 424 1,396 1,266 The unaudited pro forma financial information is based on historical information of the Company and NFP, along with certain material pro forma adjustments. The material pro forma adjustments primarily consist of (i) incremental amortization expense based on the preliminary fair values of the intangible assets acquired; (ii) interest expense to reflect Aon’s borrowings under the Senior Notes offering and delayed draw term loan; (iii) increased compensation expense relating to the issuance of certain cash and equity plans related to the NFP Transaction; (iv) nonrecurring transaction costs; (v) accounting policy alignment adjustments, and (vi) income tax impact of the aforementioned pro forma adjustments. 2023 Acquisitions On November 30, 2023, the Company completed the acquisition of 100% of the share capital of Gi&Bi S.r.l., an Italy-based insurance broker specialized in the agricultural business segment. On August 30, 2023, the Company completed the acquisition of 100% of the share capital of NGS (Uruguay) S.A., a risk management consultant firm in Uruguay. On June 22, 2023, the Company completed the acquisition of 100% of the share capital of Benefits Corredores de Seguros and Asesorías e Inversiones Benefits, a business that provides health and benefits brokerage and benefit administration in Chile. Completed Dispositions The Company completed two and three di spositions during the three and six months ended June 30, 2024, respectively, and no dispositions during the three and six months ended June 30, 2023. On May 31, 2024, Aon completed the sale of Healthy Paws, its U.S.-based managing general agent specializing in pet insurance, to Chubb Limited. There were $257 million pretax gains recognized related to dispositions for the three and six months ended June 30, 2024. There were no pretax gains recognized related to dispositions for the three and six months ended June 30, 2023. Gains recognized as a result of a disposition are included in Other income (expense) in the Condensed Consolidated Statements of Income. There were $2 million losses related to dispositions recognized in Accelerating Aon United Program expenses in the Condensed Consolidated Statements of Income for the three and six months ended June 30, 2024. There were no losses related to dispositions recognized for the three and six months ended June 30, 2023. Assets and Liabilities Held for Sale As of June 30, 2024, Aon classified certain assets and liabilities as held for sale, as the Company has committed to a plan to sell the assets and liabilities within one year. Total assets and liabilities, for disposal groups classified as held for sale within Other current assets and Other current liabilities in the Condensed Consolidated Statements of Financial Position were $359 million and $64 million , respectively. Of the $359 million total assets classified as held for sale, $156 million relate to intangible assets. Other Significant Activity On May 1, 2017, the Company completed the sale of its benefits administration and business process outsourcing business (the “Divested Business”) to an entity controlled by affiliates of The Blackstone Group L.P. (the “Buyer”) and certain designated purchasers that are direct or indirect subsidiaries of the Buyer. The Buyer purchased all of the outstanding equity interests of the Divested Business, plus certain related assets and liabilities for a purchase price of $4.3 billion in cash paid at closing and deferred consideration of up to $500 million. In the first quarter of 2024, the Company earned $82 million of deferred consideration from the Buyer and the other designated purchasers. Refer to Note 6 “Other Financial Data” for additional information.

Goodwill and Other Intangible A

Goodwill and Other Intangible Assets	6 Months Ended
Goodwill and Other Intangible Assets	Jun. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Other Intangible Assets	Goodwill and Other Intangible Assets The changes in the net carrying amount of goodwill for the six months ended June 30, 2024 are as follows (in millions): Balance as of December 31, 2023 $ 8,414 Goodwill related to current year acquisitions 7,022 Goodwill related to current year disposals (35) Foreign currency translation and other (120) Balance as of June 30, 2024 $ 15,281 Other intangible assets by asset class are as follows (in millions): June 30, 2024 December 31, 2023 Gross Carrying Amount Accumulated Net Carrying Amount Gross Carrying Amount Accumulated Net Carrying Amount Customer-related and contract-based $ 7,729 $ 1,784 $ 5,945 $ 1,873 $ 1,686 $ 187 Tradenames 812 26 786 12 12 — Technology and other 376 313 63 359 312 47 Total $ 8,917 $ 2,123 $ 6,794 $ 2,244 $ 2,010 $ 234 The estimated future amortization for finite-lived intangible assets as of June 30, 2024 is as follows (in millions): Remainder of 2024 $ 348 2025 737 2026 661 2027 602 2028 550 2029 507 Thereafter 3,389 Total $ 6,794

Debt

Debt	6 Months Ended
Debt	Jun. 30, 2024
Debt Disclosure [Abstract]
Debt	Debt Notes In June 2024, Aon Global Limited’s $600 million 3.50% Senior Notes matured and were repaid in full. On April 25, 2024, Aon North America, Inc. drew its $2 billion delayed draw term loan and used proceeds, together with the proceeds of the Senior Notes issued on March 1, 2024 described below, to pay a portion of cash consideration in connection with the NFP Transaction, to repay certain debt of NFP, and to pay related fees and expenses. The term loan matures on April 24, 2027 and is prepayable at any time. On May 28, 2024, Aon North America, Inc. repaid $300 million of the outstanding balance under the term loan facility. On April 2, 2024, Aon plc announced that its wholly owned subsidiary, Randolph Acquisition Corp., commenced cash tender offers for any and all of the outstanding 6.875% Senior Notes due 2028, 4.875% Senior Secured Notes due 2028, 7.500% Senior Secured Notes due 2030 and 8.500% Senior Secured Notes due 2031, each issued by NFP Corp. (together, the “NFP Notes”), upon the terms and subject to the conditions set forth in the Offer to Purchase and Consent Solicitation Statement, dated as of April 2, 2024. The total amount tendered pursuant to the tender offers was approximately $3.3 billion, excluding premiums. On April 26, 2024, Randolph Acquisition Corp. purchased those NFP Notes that were validly tendered and not validly withdrawn prior to April 15, 2024, effecting the early settlement of the offers (the “Early Settlement”). In addition, on April 16, 2024, NFP Corp. delivered notices of redemption of all NFP Notes not validly tendered pursuant to the offers and purchased at the Early Settlement, at a purchase price equal to the price paid to holders of the NFP Notes in connection with the Early Settlement, with a redemption date of April 26, 2024. As a result of the Early Settlement of the offers and the related redemption which occurred on April 26, 2024, no NFP Notes remain outstanding. Aon plc incurred approximately $6 million of debt extinguishment charges in the second quarter of 2024 related to NFP transaction costs. On March 1, 2024, Aon North America, Inc. issued $600 million 5.125% Senior Notes due in March 2027 , $1 billion 5.150% Senior Notes due in March 2029, $650 million 5.300% Senior Notes due in March 2031, $1.75 billion 5.450% Senior Notes due in March 2034, and $2 billion 5.750% Senior Notes due in March 2054, totaling to an aggregate amount of $6 billion. The Company intends to use the net proceeds from the offering for general corporate purposes, including a portion of which that was used to pay a portion of the cash consideration in connection with the acquisition of NFP, to repay certain debt of NFP, and to pay related fees and expenses. In November 2023, Aon Global Limited’s $350 million 4.00% Senior Notes matured and were repaid in full. On February 28, 2023, Aon Corporation, a Delaware corporation, and Aon Global Holdings plc, a public limited company formed under the laws of England and Wales, both wholly owned subsidiaries of the Company, co-issued $750 million 5.35% Senior Notes due in February 2033. The Company intends to use the net proceeds from the offering for general corporate purposes. Revolving Credit Facilities As of June 30, 2024, Aon had two primary committed credit facilities outstanding: its $1.0 billion multi-currency U.S. credit facility expiring in September 2027 and its $1.0 billion multi-currency U.S. credit facility expiring in October 2028. In aggregate, these two facilities provide $2.0 billion in available credit. Each of these primary committed credit facilities and the delayed draw term loan includes customary representations, warranties, and covenants, including financial covenants that require Aon to maintain specified ratios of adjusted consolidated EBITDA to consolidated interest expense and consolidated debt to adjusted consolidated EBITDA, in each case, tested quarterl y. Aon did not have borrowings under either of these primary committed credit facilities as of June 30, 2024 and December 31, 2023, respectively. Additionally, Aon was in compliance with the financial covenants and all other covenants contained therein during the rolling 12 months ended June 30, 2024. Commercial Paper Aon Corporation has established a U.S. commercial paper program (the “U.S. Program”) and Aon Global Holdings plc has established a European multi-currency commercial paper program (the “European Program” and, together with the U.S. Program, the “Commercial Paper Program”). Commercial paper may be issued in aggregate principal amounts of up to approximately $1.3 billion under the U.S. Program and €625 million ( $668 million at June 30, 2024 exchange rates) under the European Program, not to exceed the amount of the Company’s committed credit facilities, which was $2.0 billion at June 30, 2024. The aggregate capacity of the Commercial Paper Program remains fully backed by the Company’s committed credit facilities. The U.S. Program was fully and unconditionally guaranteed by Aon plc, Aon Global Limited, Aon North America, Inc., and Aon Global Holdings plc and the European Program was fully and unconditionally guaranteed by Aon plc, Aon Global Limited, Aon North America, Inc., and Aon Corporation. Commercial paper outstanding, which is included in Short-term debt and current portion of long-term debt in the Condensed Consolidated Statements of Financial Position, is as follows (in millions): June 30, 2024 December 31, 2023 Commercial paper outstanding $ — $ 597 The weighted average commercial paper outstanding and its related interest rates are as follows (in millions, except percentages): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Weighted average commercial paper outstanding $ 34 $ 435 $ 207 $ 414 Weighted average interest rate of commercial paper outstanding 5.50 % 4.90 % 5.63 % 4.18 %

Income Taxes

Income Taxes	6 Months Ended
Income Taxes	Jun. 30, 2024
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective tax rate on Net income was 22.9% and 23.1% for the three and six months ended June 30, 2024, respectively. The effective tax rate on Net income was 12.6% and 17.3% for the three and six months ended June 30, 2023, respectively. For the three and six months ended June 30, 2024, the tax rate was primarily driven by the geographical distribution of income and certain discrete items, including the favorable impacts of share-based payments offset by the unfavorable impact of discrete items. For the three and six months ended June 30, 2023, the tax rate was primarily driven by the geographical distribution of income and certain discrete items, including the tax benefit associated with share-based payments and the anticipated sale of certain assets and liabilities classified as held for sale. Subsequent Events Ireland, the U.K., and many E.U. member states, among others, have enacted legislation to implement the global minimum tax that are consistent with the OECD’s proposed Pillar Two tax regime. Ireland’s Pillar Two rules changed on July 24, 2024, when the last E.U. member state consented to the OECD’s administrative guidance, but there remains significant uncertainty as to how Ireland’s Pillar Two tax regime and the OECD’s past and potentially future Pillar Two guidance will ultimately apply to the Company. The Company is actively monitoring developments in this area and continues to evaluate the guidance and the potential estimated impacts this may have on its global effective tax rate, results of operations, cash flows, and financial condition in 2024.

Shareholders' Equity (Deficit)

Shareholders' Equity (Deficit)	6 Months Ended
Shareholders' Equity (Deficit)	Jun. 30, 2024
Equity [Abstract]
Shareholders' Equity (Deficit)	Shareholders’ Equity (Deficit) Ordinary Shares Aon has a share repurchase program authorized by the Company’s Board of Directors (“the Repurchase Program”). The Repurchase Program was established in April 2012 with $5.0 billion in authorized repurchases, and was increased by $5.0 billion in authorized repurchases in each of November 2014, June 2017, and November 2020, and by $7.5 billion in February 2022 for a total of $27.5 billion in repurchase authorizations. Under the Repurchase Program, the Company’s class A ordinary shares may be repurchased through the open market or in privately negotiated transactions, from time to time, based on prevailing market conditions, and will be funded from available capital. The following table summarizes the Company’s share repurchase activity (in millions, except per share data): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Shares repurchased 0.8 1.7 1.6 3.5 Average price per share $ 298.09 $ 323.96 $ 304.20 $ 314.36 Repurchase costs recorded to accumulated deficit $ 250 $ 550 $ 500 $ 1,100 At June 30, 2024, the remaining authorized amount for share repurchases under the Repurchase Program was approximately $2.8 billion. Under the Repurchase Program, the Company has repurchased a total of 170.7 million shares for an aggregate cost of approximately $24.7 billion. Weighted Average Ordinary Shares Weighted average ordinary shares outstanding are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Basic weighted average ordinary shares outstanding 212.5 204.7 205.8 205.4 Dilutive effect of potentially issuable shares 0.8 1.6 0.9 1.3 Diluted weighted average ordinary shares outstanding 213.3 206.3 206.7 206.7 Potentially issuable shares are not included in the computation of Diluted net income per share attributable to Aon shareholders if their inclusion would be antidilutive. There were 1.4 million and 0.6 million shares excluded from the calculation for the three and six months ended June 30, 2024, respectively. There were no shares excluded from the calculation for the three and six months ended June 30, 2023. Accumulated Other Comprehensive Loss Changes in Accumulated other comprehensive loss by component, net of related tax, are as follows (in millions): Change in Fair Value of Financial Instruments (1) Foreign Currency Translation Adjustments Postretirement Benefit Obligation (2) Total Balance at January 1, 2024 $ 2 $ (1,584) $ (2,791) $ (4,373) Other comprehensive income (loss) before reclassifications, net 75 (220) (13) (158) Amounts reclassified from accumulated other comprehensive income Amounts reclassified from accumulated other comprehensive income 2 — 70 72 Tax expense (1) — (18) (19) Amounts reclassified from accumulated other comprehensive income, net 1 — 52 53 Net current period other comprehensive income (loss) 76 (220) 39 (105) Balance at June 30, 2024 $ 78 $ (1,804) $ (2,752) $ (4,478) Change in Fair Value of Financial Instruments (1) Foreign Currency Translation Adjustments Postretirement Benefit Obligation (2) Total Balance at January 1, 2023 $ (11) $ (1,861) $ (2,751) $ (4,623) Other comprehensive income (loss) before reclassifications, net 7 228 (22) 213 Amounts reclassified from accumulated other comprehensive income Amounts reclassified from accumulated other comprehensive income 6 — 92 98 Tax expense (2) — (24) (26) Amounts reclassified from accumulated other comprehensive income, net 4 — 68 72 Net current period other comprehensive income (loss) 11 228 46 285 Balance at June 30, 2023 $ — $ (1,633) $ (2,705) $ (4,338) (1) Reclassifications from this category included in Accumulated other comprehensive loss are recorded in Total revenue, Interest expense, and Compensation and benefits in the Condensed Consolidated Statements of Income. Refer to Note 13 “Derivatives and Hedging” for further information regarding the Company’s derivative and hedging activity. (2) Reclassifications from this category included in Accumulated other comprehensive loss are recorded in Other income (expense) in the Condensed Consolidated Statements of Income.

Employee Benefits

Employee Benefits	6 Months Ended
Employee Benefits	Jun. 30, 2024
Retirement Benefits [Abstract]
Employee Benefits	Employee Benefits The following table provides the components of the net periodic (benefit) cost recognized in the Condensed Consolidated Statements of Income for Aon’s significant U.K., U.S., and other major pension plans, which are located in the Netherlands and Canada. Service cost is reported in Compensation and benefits and all other components are reported in Other income (expense) as follows (in millions): Three Months Ended June 30, U.K. U.S. Other 2024 2023 2024 2023 2024 2023 Service cost $ — $ — $ — $ — $ — $ — Interest cost 36 36 23 26 10 10 Expected return on plan assets, net of administration expenses (47) (48) (35) (30) (14) (12) Amortization of prior-service cost — 1 — — — — Amortization of net actuarial loss 21 19 8 8 3 4 Net periodic (benefit) cost 10 8 (4) 4 (1) 2 Loss on pension settlement — — — — — 27 Total net periodic (benefit) cost $ 10 $ 8 $ (4) $ 4 $ (1) $ 29 Six Months Ended June 30, U.K. U.S. Other 2024 2023 2024 2023 2024 2023 Service cost $ — $ — $ — $ — $ — $ — Interest cost 71 72 46 52 19 20 Expected return on plan assets, net of administration expenses (94) (94) (68) (60) (27) (24) Amortization of prior-service cost 1 1 — — — — Amortization of net actuarial loss 41 37 15 17 6 7 Net periodic (benefit) cost 19 16 (7) 9 (2) 3 Loss on pension settlement — — — — — 27 Total net periodic (benefit) cost $ 19 $ 16 $ (7) $ 9 $ (2) 30 In May 2023, to further its pension de-risking strategy, the Company settled certain pension obligations in the Netherlands through the purchase of annuities, where certain pension assets were liquidated to purchase the annuities. A non-cash settlement charge totaling $27 million was recognized in the second quarter of 2023. Contributions Assuming no additional contributions are agreed to with, or required by, the pension plan trustees, the Company expects to make total cash contributions of approximately $2 million, $53 million, and $13 million (at December 31, 2023 exchange rates) to its significant U.K., U.S., and other major pension plans, respectively, during 2024. The following table summarizes contributions made to the Company’s significant pension plans (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Contributions to U.K. pension plans $ 1 $ 1 $ 2 $ 2 Contributions to U.S. pension plans 4 5 18 21 Contributions to other major pension plans 5 2 7 8 Total contributions $ 10 $ 8 $ 27 $ 31

Derivatives and Hedging

Derivatives and Hedging	6 Months Ended
Derivatives and Hedging	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging	Derivatives and Hedging The Company is exposed to market risks, including changes in foreign currency exchange rates and interest rates. To manage the risk related to these exposures, the Company enters into various derivative instruments that reduce these risks by creating offsetting exposures. The Company does not enter into derivative transactions for trading or speculative purposes. Foreign Exchange Risk Management The Company is exposed to foreign exchange risk when it earns revenues, pays expenses, enters into monetary intercompany transfers or other transactions denominated in a currency that differs from its functional currency. The Company uses foreign exchange derivatives, typically forward contracts, options and cross currency swaps, to reduce its overall exposure to the effects of currency fluctuations on cash flows. These exposures are hedged, on average, for less than two years. These derivatives are accounted for as hedges, and changes in fair value are recorded each period in Other comprehensive income (loss) in the Condensed Consolidated Statements of Comprehensive Income. The Company also uses foreign exchange derivatives, typically forward contracts and options, to economically hedge the currency exposure of the Company’s global liquidity profile, including monetary assets or liabilities that are denominated in a non-functional currency of an entity, typically on a rolling 90-day basis, but may be for up to one year in the future. These derivatives are not accounted for as hedges, and changes in fair value are recorded each period in Other income (expense) in the Condensed Consolidated Statements of Income. The notional and fair values of derivative instruments are as follows (in millions): Notional Amount Net Amount of Derivative Assets Presented in the Statements of Financial Position (1) Net Amount of Derivative Liabilities Presented in the Statements of Financial Position (2) June 30, December 31, June 30, December 31, June 30, December 31, Foreign exchange contracts Accounted for as hedges $ 712 $ 1,724 $ 36 $ 34 $ — $ 2 Not accounted for as hedges (3) 492 382 — 2 1 1 Total $ 1,204 $ 2,106 $ 36 $ 36 $ 1 $ 3 (1) Included within Other current assets ($21 million at June 30, 2024 and $17 million at December 31, 2023) or Other non-current assets ($15 million at June 30, 2024 and $19 million at December 31, 2023). (2) Included within Other current liabilities ($1 million at June 30, 2024 and $3 million at December 31, 2023). (3) These contracts typically are for 90-day durations and executed close to the last day of the most recent reporting month, thereby resulting in nominal fair values at the balance sheet date. The amounts of derivative gains recognized in the Condensed Consolidated Financial Statements are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Gain recognized in Accumulated other comprehensive loss $ 4 $ 9 $ 101 $ 9 The amounts of derivative gains (losses) reclassified from Accumulated other comprehensive loss to the Condensed Consolidated Statements of Income are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Gain (loss) recognized in Total revenue $ 2 $ (1) $ (2) $ (6) The Company estimates that approximately $6 million of pretax gains currently included within Accumulated other comprehensive loss will be reclassified into earnings in the next twelve months. During the three and six months ended June 30, 2024, the Company recorded losses of $6 million and $9 million, respectively, in Other income (expense) for foreign exchange derivatives not designated or qualifying as hedges. During the three and six months ended June 30, 2023, the Company recorded gains of $28 million and $37 million, respectively, in Other income (expense) for foreign exchange derivatives not designated or qualifying as hedges.

Fair Value Measurements and Fin

Fair Value Measurements and Financial Instruments	6 Months Ended
Fair Value Measurements and Financial Instruments	Jun. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements and Financial Instruments	Fair Value Measurements and Financial Instruments Accounting standards establish a three-tier fair value hierarchy that prioritizes the inputs used in measuring fair values as follows: • Level 1 — observable inputs such as quoted prices for identical assets in active markets; • Level 2 — inputs other than quoted prices for identical assets in active markets, that are observable either directly or indirectly; and • Level 3 — unobservable inputs in which there is little or no market data which requires the use of valuation techniques and the development of assumptions. The following methods and assumptions are used to estimate the fair values of the Company’s financial instruments: Money market funds consist of institutional prime, treasury, and government money market funds. The Company reviews treasury and government money market funds to obtain reasonable assurance that the fund net asset value is $1 per share, and reviews the floating net asset value of institutional prime money market funds for reasonableness. Equity investments consist of equity securities and equity derivatives valued using the closing stock price on a national securities exchange. Over-the-counter equity derivatives are valued using observable inputs such as underlying prices of the underlying security and volatility. On a sample basis, the Company reviews the listing of Level 1 equity securities in the portfolio, agrees the closing stock prices to a national securities exchange, and independently verifies the observable inputs for Level 2 equity derivatives and securities. Fixed income investments consist of certain categories of bonds and derivatives. Corporate, government, and agency bonds are valued by pricing vendors who estimate fair value using recently executed transactions and proprietary models based on observable inputs, such as interest rate spreads, yield curves, and credit risk. Asset-backed securities are valued by pricing vendors who estimate fair value using DCF models utilizing observable inputs based on trade and quote activity of securities with similar features. Fixed income derivatives are valued by pricing vendors using observable inputs such as interest rates and yield curves. The Company obtains an understanding of the models, inputs, and assumptions used in developing prices provided by its vendors through discussions with the fund managers. The Company independently verifies the observable inputs, as well as assesses assumptions used for reasonableness based on relevant market conditions and internal Company guidelines. If an assumption is deemed unreasonable, based on internal Company guidelines, it is then reviewed by management and the fair value estimate provided by the vendor is adjusted, if deemed appropriate. These adjustments do not occur frequently and historically are not material to the fair value estimates used in the Condensed Consolidated Financial Statements. Derivatives are carried at fair value, based upon industry standard valuation techniques that use, where possible, current market-based or independently sourced pricing inputs, such as interest rates, currency exchange rates, or implied volatility. Debt is carried at outstanding principal balance, less any unamortized issuance costs, discount or premium. Fair value is based on quoted market prices or estimates using DCF analyses based on current borrowing rates for similar types of borrowing arrangements. The following tables present the categorization of the Company’s assets and liabilities that are measured at fair value on a recurring basis at June 30, 2024 and December 31, 2023 (in millions): Fair Value Measurements Using Balance at June 30, 2024 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Money market funds (1) $ 2,983 $ 2,983 $ — $ — Other investments Government bonds $ 1 $ — $ 1 $ — Derivatives (2) Gross foreign exchange contracts $ 49 $ — $ 49 $ — Liabilities Derivatives (2) Gross foreign exchange contracts $ 15 $ — $ 15 $ — Fair Value Measurements Using Balance at December 31, 2023 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Money market funds (1) $ 3,204 $ 3,204 $ — $ — Other investments Government bonds $ 1 $ — $ 1 $ — Derivatives (2) Gross foreign exchange contracts $ 49 $ — $ 49 $ — Liabilities 0 Derivatives (2) Gross foreign exchange contracts $ 16 $ — $ 16 $ — (1) Included within Fiduciary assets or Short-term investments in the Condensed Consolidated Statements of Financial Position, depending on their nature and initial maturity. (2) Refer to Note 13 “Derivatives and Hedging” for additional information regarding the Company’s derivatives and hedging activity. There were no transfers of assets or liabilities between fair value hierarchy levels in the three and six months ended June 30, 2024 or 2023. The Company recognized no realized or unrealized gains or losses in the Condensed Consolidated Statements of Income during the three and six months ended June 30, 2024 or 2023 related to assets and liabilities measured at fair value using unobservable inputs. The fair value of debt is classified as Level 2 of the fair value hierarchy. The following table provides the carrying value and fair value for the Company’s term debt (in millions): June 30, 2024 December 31, 2023 Carrying Value Fair Value Carrying Value Fair Value Current portion of long-term debt $ — $ — $ 600 $ 595 Long-term debt $ 17,610 $ 16,560 $ 9,995 $ 9,223

Claims, Lawsuits, and Other Con

Claims, Lawsuits, and Other Contingencies	6 Months Ended
Claims, Lawsuits, and Other Contingencies	Jun. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Claims, Lawsuits, and Other Contingencies	Claims, Lawsuits, and Other Contingencies Legal Aon and its subsidiaries are subject to numerous claims, tax assessments, lawsuits, and proceedings that arise in the ordinary course of business, which frequently include E&O claims. The damages claimed in these matters are or may be substantial, including, in many instances, claims for punitive, treble, or extraordinary damages. While Aon maintains meaningful E&O insurance and other insurance programs to provide protection against certain losses that arise in such matters, Aon has exhausted or materially depleted its coverage under some of the policies that protect the Company and, consequently, is self-insured or materially self-insured for some claims, including coverage from Aon’s self-insurance program. Accruals for these exposures, and related insurance receivables, when applicable, are included in the Condensed Consolidated Statements of Financial Position and have been recognized in Other general expense in the Condensed Consolidated Statements of Income to the extent that losses are deemed probable and are reasonably estimable. These amounts are adjusted from time to time as developments warrant. Matters that are not probable and reasonably estimable are not accrued for in the financial statements. The Company’s contingencies and exp osures are subject to significant uncertainties, and the determination of likelihood of a loss and estimating any such loss can be complex. The Company is therefore, in certain matters, unable to estimate the range of reasonably possible loss. Although management at present believes that the ultimate outcome of such matters, individually or in the aggregate, will not have a material adverse effect on the consolidated financial position of Aon, legal proceedings are subject to inherent uncertainties and unfavorable rulings or other events. Unfavorable resolutions could include substantial monetary or punitive damages imposed on Aon or its subsidiaries. If unfavorable outcomes of these matters were to occur, future results of operations or cash flows for any particular quarterly or annual period could be materially adversely affected. Certain significant legal proceedings involving us or our subsidiaries are described below. Current Matters Aon faces legal action arising out of a fatal plane crash in November 2016. Aon U.K. Limited placed an aviation civil liability reinsurance policy for the Bolivian insurer of the airline. After the crash, the insurer determined that there was no coverage under the airline’s insurance policy due to the airline’s breach of various policy conditions. In November 2018, the owner of the aircraft filed a claim in Bolivia against Aon, the airline, the insurer and the insurance broker. The claim is for $16 million plus any liability the owner has to third parties. In November 2019, a federal prosecutor in Brazil filed a public civil action naming three Aon entities as defendants, along with the airline, the insurer and the lead reinsurer. That claim seeks pecuniary damages for families affected by the crash in the sum of $300 million; or, in the alternative, $50 million; or, in the alternative, $25 million; plus “moral damages” of an equivalent sum. Separately, in March 2020, the Brazilian Federal Senate invited Aon to give evidence to a Parliamentary Commission of Inquiry in an investigation into the accident. Aon cooperated with that inquiry. In August 2020, 43 individuals (surviving passengers and estates of the deceased) filed a motion in the Circuit Court of the 11th Judicial Circuit in and for Miami-Dade County, Florida, seeking permission to commence proceedings against Aon (and the insurer and reinsurers) for claims totaling $844 million. Finally, in April 2021, representatives of 16 passengers issued a claim against Aon in the High Court in England seeking damages under the Fatal Accidents Act 1976 in the sum of £29 million ( $37 million at June 30, 2024 exchange rates). In February 2024, the claim brought by representatives of 16 passengers in the High Court in England was dismissed pursuant to an agreement among the parties. In December 2022, the High Court in England granted an anti-suit injunction, restricting the 43 individuals who previously filed a motion in the Circuit Court of the 11th Judicial Circuit in and for Miami Dade County, Florida, from continuing litigation in the Circuit Court of the 11th Judicial Circuit against Aon. Aon believes that it has meritorious defenses and intends to vigorously defend itself against the remaining claims. Certain of the Company’s clients and counterparties have initiated or indicated that they may initiate legal proceedings against the Company following allegations in July 2023 that fraudulent letters of credit were issued in the name of third-party banks in connection with transactions for which capital was arranged by Vesttoo Ltd. (“Vesttoo”). Vesttoo is one of the third parties that identifies capital providers to collateralize insurance and reinsurance obligations of the Company’s clients and counterparties. In certain transactions in which Vesttoo identified third party capital providers to collateralize reinsurance obligations, including transactions in which the Company or its affiliates provided brokerage or other services, some letters of credit from third party banks are alleged to have been fraudulent. The pending or threatened legal proceedings against the Company allege, among other theories of liability, that in certain circumstances the Company failed to comply with its alleged duty to procure appropriate letters of credit. In particular, on November 30, 2023, Clear Blue Insurance Company and certain of its affiliates filed a lawsuit in New York State Supreme Court against Aon plc and Aon Insurance Managers (Bermuda) Ltd. alleging such claims. While Aon has settled and/or is in discussions to settle certain claims, Aon believes that it has meritorious defenses and intends to vigorously defend itself against those claims that are not settled. In the fourth quarter of 2023, the Company recognized actual or anticipated legal settlement expenses in connection with these matters of $197 million, of which a potentially significant amount may be recoverable in future periods. Aon may also seek recourse against third parties where appropriate, including in connection with bankruptcy proceedings filed by Vesttoo in the Bankruptcy Court for the U.S. District of Delaware. In addition, in August 2023, joint provisional liquidators were appointed over one of the Company’s subsidiaries in Bermuda with respect to segregated accounts that were impacted by the allegedly fraudulent letters of credit. The joint provisional liquidators were released from their appointment on July 3, 2024. Aon continues to cooperate with regulators in Bermuda, and other regulatory authorities could initiate investigations or proceedings against the Company or third parties. Guarantees and Indemnifications The Company provides a variety of guarantees and indemnifications to its customers and others. The maximum potential amount of future payments represents the notional amounts that could become payable under the guarantees and indemnifications if there were a total default by the guaranteed parties, without consideration of possible recoveries under recourse provisions or other methods. These amounts may bear no relationship to the expected future payments, if any, for these guarantees and indemnifications. Any anticipated amounts payable are included in the Condensed Consolidated Financial Statements, and are recorded at fair value. The Company expects that, as prudent business interests dictate, additional guarantees and indemnifications may be issued from time to time. Guarantee of Registered Securities On June 22, 2023, Aon plc, Aon Global Limited, Aon Global Holdings plc, Aon Corporation, and Aon North America, Inc., and The Bank of New York Mellon Trust Company, N.A., as trustee (the “Trustee”), as applicable, entered into supplemental indentures, each dated June 22, 2023, amending each of the following indentures (as amended, supplemented or modified from time to time) to add for the benefit of the holders of the instruments issued thereunder a full and unconditional guarantee of Aon North America, Inc. thereunder: (i) Second Amended and Restated Indenture, dated April 1, 2020, among Aon Corporation, Aon plc, Aon Global Limited, Aon Global Holdings plc and the Trustee (amending and restating the Amended and Restated Indenture, dated April 2, 2012, amending and restating the Indenture, dated January 13, 1997); (ii) Second Amended and Restated Indenture, dated April 1, 2020, among Aon Corporation, Aon plc, Aon Global Limited, Aon Global Holdings plc and the Trustee (amending and restating the Amended and Restated Indenture, dated April 2, 2012, amending and restating the Indenture, dated September 10, 2010); (iii) Amended and Restated Indenture, dated April 1, 2020, among Aon plc, Aon Corporation, Aon Global Limited, Aon Global Holdings plc and the Trustee (amending and restating the Indenture, dated December 12, 2012); (iv) Second Amended and Restated Indenture, dated April 1, 2020, among Aon plc, Aon Corporation, Aon Global Limited, Aon Global Holdings plc and the Trustee (amending and restating the Amended and Restated Indenture, dated May 20, 2015, amending and restating the Indenture, dated May 24, 2013); (v) Amended and Restated Indenture, dated April 1, 2020, among Aon plc, Aon Corporation, Aon Global Limited, Aon Global Holdings plc and the Trustee (amending and restating the Indenture, dated November 13, 2015); and (vi) Amended and Restated Indenture, dated April 1, 2020, among Aon Corporation, Aon plc, Aon Global Limited, Aon Global Holdings plc and the Trustee (amending and restating the Indenture, dated December 3, 2018). Letters of Credit Aon has entered into a number of arrangements whereby the Company’s performance on certain obligations is guaranteed by a third party through the issuance of LOCs. The Company had total LOCs outstanding of approximately $145 million at June 30, 2024, and $86 million at December 31, 2023. These LOCs cover the beneficiaries related to certain of Aon’s U.S. and Canadian secure n on-qualified pension plan schemes, reinsurance obligations related to Aon’s own E&O liability insurance program, and secure deductible retentions for Aon’s own workers compensation program. The Company has also obtained LOCs to cover contingent payments for taxes and other business obligations to third parties, and other guarantees for miscellaneous purposes at its international subsidiaries. Premium Payments The Company has certain contractual contingent guarantees for premium payments owed by clients to certain insurance companies. The maximum exposure with respect to such contractual contingent guarantees was approximately $138 million at June 30, 2024 compared to $194 million at December 31, 2023.

Segment Information

Segment Information	6 Months Ended
Segment Information	Jun. 30, 2024
Segment Reporting [Abstract]
Segment Information	Segment Information The Company operates as one segment that includes all of Aon’s operations, which as a global professional services firm provides a broad range of Risk and Human Capital Solutions through four solution lines — Commercial risk, Reinsurance, Health, and Wealth, which make up its principal products and services. The CODM assesses the performance of the Company and allocates resources based on one segment: Aon United. The Company’s reportable operating segment has been determined using a management approach, which is consistent with the basis and manner in which the CODM uses financial information for the purposes of allocating resources and evaluating performance. The CODM assesses performance and allocates resources based on total Aon results against its key four metrics, expense discipline, and collaborative behaviors that maximize value for Aon and its shareholders, regardless of which solution line it benefits. As Aon operates as one segment, segment profit or loss is consistent with consolidated reporting as disclosed in the Condensed Consolidated Statements of Income. Refer to Note 3 “Revenue from Contracts with Customers” for further information on revenue by principal service line.

Accounting Principles and Pra_2

Accounting Principles and Practices (Policies)	6 Months Ended
Accounting Principles and Practices (Policies)	Jun. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying Condensed Consolidated Financial Statements and Notes thereto have been prepared in accordance with U.S. GAAP. The Condensed Consolidated Financial Statements include the accounts of Aon plc and all of its controlled subsidiaries (“Aon” or the “Company”). Intercompany accounts and transactions have been eliminated. The Condensed Consolidated Financial Statements include, in the opinion of management, all adjustments (consisting of normal recurring adjustments and reclassifications) necessary to present fairly the Company’s consolidated financial position, results of operations, and cash flows for all periods presented. Certain information and disclosures normally included in the Consolidated Financial Statements prepared in accordance with U.S. GAAP have been condensed or omitted. The Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements and Notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. The results for the three and six months ended June 30, 2024 are not necessarily indicative of operating results that may be expected for the full year ending December 31, 2024.
Use of Estimates	Use of Estimates The preparation of the accompanying Condensed Consolidated Financial Statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosures of contingent assets and liabilities at the date of the Condensed Consolidated Financial Statements, and the reported amounts of reserves and expenses. These estimates and assumptions are based on management’s best estimates and judgments. Management evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors, including the current economic environment. Management believes its estimates to be reasonable given the current facts available. Aon adjusts such estimates and assumptions when facts and circumstances dictate. Illiquid credit markets, volatile equity markets, and foreign currency exchange rate movements increase the uncertainty inherent in such estimates and assumptions. As future events and their effects cannot be determined with precision, actual results could differ significantly from these estimates. Changes in estimates resulting from continuing changes in the economic environment would, if applicable, be reflected in the Condensed Consolidated Financial Statements in future periods.
Contingent Consideration	Contingent Consideration Contingent consideration may be paid to the former owners of the business and typically will involve the acquired entity reaching specific financial results over a designated period. Contingent consideration payables are recorded at fair value and are included in the purchase price consideration at the time of the acquisition. Subsequent changes in the fair value of contingent consideration obligations are recorded in the Condensed Consolidated Statements of Income. The fair value of contingent consideration payables is based on the expected future payments to be made to the sellers of the acquired businesses in accordance with the provisions outlined in the respective purchase agreements. In determining fair value of the contingent consideration, the acquired business’s future performance is estimated using financial projections for the acquired business and measured against performance targets specified in each purchase agreement. Contingent consideration liabilities are classified as Level 3 because of the Company’s reliance on unobservable inputs.
Principles of Consolidations	Principles of Consolidations The accompanying Condensed Consolidated Financial Statements include the accounts of Aon plc and those entities in which the Company has a controlling financial interest. To determine if Aon holds a controlling financial interest in an entity, the Company first evaluates if it is required to apply the variable interest model to the entity, otherwise, the entity is evaluated under the voting interest model. When Aon holds rights that give it the power to direct the activities of a VIE that most significantly impact the VIE’s economic performance, combined with a variable interest that gives the right to receive potentially significant benefits or the obligation to absorb potentially significant losses, the Company has a controlling financial interest in that VIE. If the Company is the primary beneficiary of a VIE, the Company consolidates the entity and reflects any relevant noncontrolling interest of other beneficiaries of that entity on the Statement of Consolidated Financial Position. Aon’s interest in VIEs as of June 30, 2024 predominantly relates to assets and liabilities acquired through the acquisition of NFP and are subject to purchase accounting adjustments. Total assets related to consolidated VIEs are approximately 1% of the Company’s Total assets on the Condensed Consolidated Statements of Financial Position for the period ended June 30, 2024. Aon holds a controlling financial interest in entities that are not VIEs when it, directly or indirectly holds more than 50% of the voting rights and the noncontrolling interest holders do not hold substantive participating rights.
Redeemable Non-controlling Interest	Redeemable Noncontrolling Interests Redeemable noncontrolling interests represent interests for certain consolidated entities which are subject to redemption rights held by the noncontrolling interests owners outside of the Company’s control at fixed or determinable prices and dates. The interests are initially recorded at fair value and in subsequent reporting periods are adjusted to the estimated redemption value. The adjustments to the redemption value are recorded to additional paid-in capital or retained earnings, when appropriate, on the Condensed Consolidated Statements of Financial Position. The Redeemable noncontrolling interests are considered temporary equity and reported outside of permanent equity on the Condensed Consolidated Statements of Financial Position. The interests are recorded at the greater of the carrying amount adjusted for the noncontrolling interest’s share of net income (loss) and distributions or its redemption value.
New Accounting Pronouncements	New Accounting Pronouncements Accounting Standards Issued But Not Yet Adopted Improvements to Reportable Segment Disclosures In November 2023, the FASB issued new accounting guidance, requiring new segment disclosures under ASC 280, Segment Reporting, including disclosure of significant segment expense categories and amounts that are regularly reported to the CODM and included in the segment’s profit or loss. Additionally, all disclosure requirements under ASC 280, including new requirements under this new guidance, will be required on an interim basis. The new guidance is effective for Aon for the year ended December 31, 2024 and interim periods thereafter, with early adoption permitted. An entity will apply the new guidance on a retrospective basis for all periods presented. The Company is currently evaluating the impact the guidance will have on the Notes to Consolidated Financial Statements. Improvements to Income Tax Disclosures In December 2023, the FASB issued new accounting guidance under ASC 740, Income Taxes, which requires additional income tax disclosures on an annual basis, including disaggregation of information presented within the reconciliation of the expected tax to the reported tax by specific categories, with certain reconciling items 5% or greater broken out by nature and/or jurisdiction. The new guidance also requires disclosure of income taxes paid, net of refunds, broken out by federal, state/local, and foreign, including disclosure of individual jurisdictions when greater than 5% of total net income taxes paid. The new guidance is effective for Aon for the year ended December 31, 2025, with early adoption permitted. The Company is evaluating the period of adoption and transition approach, as well as the impact the disclosures will have on the Notes to Consolidated Financial Statements.
Derivatives and Hedging	The Company is exposed to market risks, including changes in foreign currency exchange rates and interest rates. To manage the risk related to these exposures, the Company enters into various derivative instruments that reduce these risks by creating offsetting exposures. The Company does not enter into derivative transactions for trading or speculative purposes. Foreign Exchange Risk Management The Company is exposed to foreign exchange risk when it earns revenues, pays expenses, enters into monetary intercompany transfers or other transactions denominated in a currency that differs from its functional currency. The Company uses foreign exchange derivatives, typically forward contracts, options and cross currency swaps, to reduce its overall exposure to the effects of currency fluctuations on cash flows. These exposures are hedged, on average, for less than two years. These derivatives are accounted for as hedges, and changes in fair value are recorded each period in Other comprehensive income (loss) in the Condensed Consolidated Statements of Comprehensive Income. The Company also uses foreign exchange derivatives, typically forward contracts and options, to economically hedge the currency exposure of the Company’s global liquidity profile, including monetary assets or liabilities that are denominated in a non-functional currency of an entity, typically on a rolling 90-day basis, but may be for up to one year in the future. These derivatives are not accounted for as hedges, and changes in fair value are recorded each period in Other income (expense) in the Condensed Consolidated Statements of Income.
Fair Value Measurements and Financial Instruments	Accounting standards establish a three-tier fair value hierarchy that prioritizes the inputs used in measuring fair values as follows: • Level 1 — observable inputs such as quoted prices for identical assets in active markets; • Level 2 — inputs other than quoted prices for identical assets in active markets, that are observable either directly or indirectly; and • Level 3 — unobservable inputs in which there is little or no market data which requires the use of valuation techniques and the development of assumptions. The following methods and assumptions are used to estimate the fair values of the Company’s financial instruments: Money market funds consist of institutional prime, treasury, and government money market funds. The Company reviews treasury and government money market funds to obtain reasonable assurance that the fund net asset value is $1 per share, and reviews the floating net asset value of institutional prime money market funds for reasonableness. Equity investments consist of equity securities and equity derivatives valued using the closing stock price on a national securities exchange. Over-the-counter equity derivatives are valued using observable inputs such as underlying prices of the underlying security and volatility. On a sample basis, the Company reviews the listing of Level 1 equity securities in the portfolio, agrees the closing stock prices to a national securities exchange, and independently verifies the observable inputs for Level 2 equity derivatives and securities. Fixed income investments consist of certain categories of bonds and derivatives. Corporate, government, and agency bonds are valued by pricing vendors who estimate fair value using recently executed transactions and proprietary models based on observable inputs, such as interest rate spreads, yield curves, and credit risk. Asset-backed securities are valued by pricing vendors who estimate fair value using DCF models utilizing observable inputs based on trade and quote activity of securities with similar features. Fixed income derivatives are valued by pricing vendors using observable inputs such as interest rates and yield curves. The Company obtains an understanding of the models, inputs, and assumptions used in developing prices provided by its vendors through discussions with the fund managers. The Company independently verifies the observable inputs, as well as assesses assumptions used for reasonableness based on relevant market conditions and internal Company guidelines. If an assumption is deemed unreasonable, based on internal Company guidelines, it is then reviewed by management and the fair value estimate provided by the vendor is adjusted, if deemed appropriate. These adjustments do not occur frequently and historically are not material to the fair value estimates used in the Condensed Consolidated Financial Statements. Derivatives are carried at fair value, based upon industry standard valuation techniques that use, where possible, current market-based or independently sourced pricing inputs, such as interest rates, currency exchange rates, or implied volatility. Debt is carried at outstanding principal balance, less any unamortized issuance costs, discount or premium. Fair value is based on quoted market prices or estimates using DCF analyses based on current borrowing rates for similar types of borrowing arrangements.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	6 Months Ended
Revenue from Contracts with Customers (Tables)	Jun. 30, 2024
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregation of Revenue	The following table summarizes revenue from contracts with customers by principal service line (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Commercial Risk Solutions $ 2,015 $ 1,774 $ 3,823 $ 3,552 Reinsurance Solutions 635 607 1,802 1,684 Health Solutions 662 447 1,395 1,118 Wealth Solutions 463 352 833 702 Eliminations (15) (3) (23) (8) Total revenue $ 3,760 $ 3,177 $ 7,830 $ 7,048 Consolidated revenue from contracts with customers by geographic area, which is attributed on the basis of where the services are performed, is as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 United States $ 1,837 $ 1,427 $ 3,349 $ 2,922 Americas other than United States 362 308 685 609 United Kingdom 548 506 1,131 1,060 Ireland 35 28 68 58 Europe, Middle East, & Africa other than United Kingdom and Ireland 566 512 1,775 1,614 Asia Pacific 412 396 822 785 Total revenue $ 3,760 $ 3,177 $ 7,830 $ 7,048
Schedule of Capitalized Contract Cost	An analysis of the changes in the net carrying amount of costs to fulfill contracts with customers are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Balance at beginning of period $ 269 $ 257 $ 370 $ 355 Additions 386 355 766 717 Amortization (390) (373) (868) (835) Impairment — — — — Foreign currency translation and other (1) 3 (4) 5 Balance at end of period $ 264 $ 242 $ 264 $ 242 An analysis of the changes in the net carrying amount of costs to obtain contracts with customers are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Balance at beginning of period $ 194 $ 183 $ 195 $ 185 Additions 18 13 32 23 Amortization (14) (13) (27) (25) Impairment — — — — Foreign currency translation and other (2) 3 (4) 3 Balance at end of period $ 196 $ 186 $ 196 $ 186

Accelerating Aon United Progr_2

Accelerating Aon United Program (Tables)	6 Months Ended
Accelerating Aon United Program (Tables)	Jun. 30, 2024
Restructuring and Related Activities [Abstract]
Schedule of Restructuring Liabilities for the Program	The changes in the Company’s liabilities for the Program as of June 30, 2024 are as follows (in millions): Technology and other Workforce optimization Asset impairments Total Liability balance as of January 1, 2024 $ 14 $ 86 $ — $ 100 Charges 51 145 55 251 Cash payments (29) (69) — (98) Foreign currency translation and other — (3) — (3) Non-cash charges (1) (27) (10) (55) (92) Liability balance as of June 30, 2024 $ 9 $ 149 $ — $ 158 Total costs incurred from inception to date $ 65 $ 248 $ 73 $ 386 (1)

Other Financial Data (Tables)

Other Financial Data (Tables)	6 Months Ended
Other Financial Data (Tables)	Jun. 30, 2024
Other Financial Data [Abstract]
Schedule of Other Income (Expense)	Other income (expense) consists of the following (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Gain from sales of businesses $ 257 $ — $ 257 $ — Foreign currency remeasurement 5 (37) 9 (56) Equity earnings 1 (1) 3 2 Pension and other postretirement (11) (43) (21) (60) Extinguishment of debt (6) — (6) — Financial instruments and other (1) (10) 22 69 30 Total $ 236 $ (59) $ 311 $ (84) (1) In first quarter of 2024, an $82 million
Schedule of Allowance for Doubtful Accounts	Changes in the net carrying amount of allowance for doubtful accounts are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Balance at beginning of period $ 81 $ 83 $ 79 $ 76 Provision 6 2 11 9 Accounts written off, net of recoveries — (3) (2) (3) Foreign currency translation and other — 1 (1) 1 Balance at end of period $ 87 $ 83 $ 87 $ 83
Schedule of Other Current Assets	The components of Other current assets are as follows (in millions): As of June 30, December 31, Assets held for sale (1) $ 359 $ 354 Costs to fulfill contracts with customers (2) 264 370 Prepaid expenses 176 100 Taxes receivable 37 35 Other 227 137 Total $ 1,063 $ 996 (1) Refer to Note 7 “Acquisitions and Dispositions of Businesses” for further information. (2) Refer to Note 3 “Revenue from Contracts with Customers” for further information.
Schedule of Other Non-current Assets	The components of Other non-current assets are as follows (in millions): As of June 30, December 31, Costs to obtain contracts with customers (1) $ 196 $ 195 Taxes receivable 92 100 Investments 83 45 Leases 17 26 Other 241 140 Total $ 629 $ 506 (1) Refer to Note 3 “Revenue from Contracts with Customers” for further information.
Schedule of Other Current Liabilities	The components of Other current liabilities are as follows (in millions): As of June 30, December 31, Deferred revenue (1) $ 391 $ 270 Taxes payable 337 291 Leases 203 182 Contingent consideration 106 — Liabilities held for sale (2) 64 69 Other 1,209 1,066 Total $ 2,310 $ 1,878 (1) During the three and six months ended June 30, 2024, revenue of $199 million and $378 million, respectively, was recognized in the Condensed Consolidated Statements of Income. During the three and six months ended June 30, 2023, revenue of $169 million and $336 million, respectively, was recognized in the Condensed Consolidated Statements of Income. (2) Refer to Note 7 “Acquisitions and Dispositions of Businesses” for further information.
Schedule of Other Non-current Liabilities	The components of Other non-current liabilities are as follows (in millions): As of June 30, December 31, Taxes payable (1) $ 848 $ 827 Contingent consideration 91 — Compensation and benefits 59 59 Deferred revenue 34 33 Leases — 10 Other 103 145 Total $ 1,135 $ 1,074 (1) Includes $72 million for the non-current portion of the one-time mandatory transition tax on accumulated foreign earnings as of December 31, 2023.

Acquisitions and Dispositions_2

Acquisitions and Dispositions of Businesses (Tables)	6 Months Ended
Acquisitions and Dispositions of Businesses (Tables)	Jun. 30, 2024
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
Schedule of Consideration Transferred and Preliminary Value of Intangible Assets	The preliminary fair values of consideration transferred, assets acquired, liabilities assumed, and redeemable and nonredeemable noncontrolling interests are subject to adjustment when purchase accounting is finalized. The following table includes these amounts recognized as a result of the Company’s acquisitions (in millions): Six months ended June 30, 2024 NFP Acquisition Other Acquisitions Total Consideration transferred: Cash $ 3,247 $ 109 $ 3,356 Deferred and contingent consideration — 7 7 Class A ordinary shares issued 5,882 — 5,882 Aggregate consideration transferred $ 9,129 $ 116 $ 9,245 Assets acquired: Cash and cash equivalents $ 293 $ 3 $ 296 Receivables 321 3 324 Fiduciary assets (1) 411 6 417 Goodwill 6,953 69 7,022 Other intangible assets: Customer-related and contract-based 5,825 50 5,875 Tradenames 800 — 800 Technology and other 25 1 26 Operating lease right-of-use assets 143 2 145 Current assets 110 3 113 Non-current assets 169 1 170 Total assets acquired 15,050 138 15,188 Liabilities assumed: Accounts payable and accrued liabilities $ 283 $ 8 $ 291 Fiduciary liabilities 411 6 417 Current liabilities 227 — 227 Long-term debt 3,422 — 3,422 Non-current operating lease liabilities 125 2 127 Deferred tax liabilities 1,123 6 1,129 Non-current liabilities 142 — 142 Total liabilities assumed 5,733 22 5,755 Less: Fair value of redeemable noncontrolling interests (103) — (103) Less: Fair value of nonredeemable noncontrolling interests (85) — (85) Net assets acquired $ 9,129 $ 116 $ 9,245 (1)
Schedule of Pro Forma Information	The following table presents the NFP revenue and earnings as reported in the Company’s Condensed Consolidated Statements of Income (in millions): Three Months Ended June 30, 2024 Revenue $ 442 Net loss attributable to Aon shareholders $ (19) Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Revenue $ 3,910 $ 3,729 $ 8,528 $ 8,099 Net income attributable to Aon shareholders 465 424 1,396 1,266

Goodwill and Other Intangible_2

Goodwill and Other Intangible Assets (Tables)	6 Months Ended
Goodwill and Other Intangible Assets (Tables)	Jun. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in the Net Carrying Amount of Goodwill by Operating Segment	The changes in the net carrying amount of goodwill for the six months ended June 30, 2024 are as follows (in millions): Balance as of December 31, 2023 $ 8,414 Goodwill related to current year acquisitions 7,022 Goodwill related to current year disposals (35) Foreign currency translation and other (120) Balance as of June 30, 2024 $ 15,281
Schedule of Other Intangible Assets by Asset Class	Other intangible assets by asset class are as follows (in millions): June 30, 2024 December 31, 2023 Gross Carrying Amount Accumulated Net Carrying Amount Gross Carrying Amount Accumulated Net Carrying Amount Customer-related and contract-based $ 7,729 $ 1,784 $ 5,945 $ 1,873 $ 1,686 $ 187 Tradenames 812 26 786 12 12 — Technology and other 376 313 63 359 312 47 Total $ 8,917 $ 2,123 $ 6,794 $ 2,244 $ 2,010 $ 234
Schedule of Estimated Future Amortization Expense on Intangible Assets	The estimated future amortization for finite-lived intangible assets as of June 30, 2024 is as follows (in millions): Remainder of 2024 $ 348 2025 737 2026 661 2027 602 2028 550 2029 507 Thereafter 3,389 Total $ 6,794

Debt (Tables)

Debt (Tables)	6 Months Ended
Debt (Tables)	Jun. 30, 2024
Debt Disclosure [Abstract]
Schedule of Commercial Paper Outstanding	Commercial paper outstanding, which is included in Short-term debt and current portion of long-term debt in the Condensed Consolidated Statements of Financial Position, is as follows (in millions): June 30, 2024 December 31, 2023 Commercial paper outstanding $ — $ 597 The weighted average commercial paper outstanding and its related interest rates are as follows (in millions, except percentages): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Weighted average commercial paper outstanding $ 34 $ 435 $ 207 $ 414 Weighted average interest rate of commercial paper outstanding 5.50 % 4.90 % 5.63 % 4.18 %

Shareholders' Equity (Deficit)

Shareholders' Equity (Deficit) (Tables)	6 Months Ended
Shareholders' Equity (Deficit) (Tables)	Jun. 30, 2024
Equity [Abstract]
Schedule of Share Repurchase Activity	The following table summarizes the Company’s share repurchase activity (in millions, except per share data): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Shares repurchased 0.8 1.7 1.6 3.5 Average price per share $ 298.09 $ 323.96 $ 304.20 $ 314.36 Repurchase costs recorded to accumulated deficit $ 250 $ 550 $ 500 $ 1,100
Schedule of Components of Weighted Average Number of Shares Outstanding	Weighted average ordinary shares outstanding are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Basic weighted average ordinary shares outstanding 212.5 204.7 205.8 205.4 Dilutive effect of potentially issuable shares 0.8 1.6 0.9 1.3 Diluted weighted average ordinary shares outstanding 213.3 206.3 206.7 206.7
Schedule of Components of Accumulated Other Comprehensive Loss, Net of Related Tax	Changes in Accumulated other comprehensive loss by component, net of related tax, are as follows (in millions): Change in Fair Value of Financial Instruments (1) Foreign Currency Translation Adjustments Postretirement Benefit Obligation (2) Total Balance at January 1, 2024 $ 2 $ (1,584) $ (2,791) $ (4,373) Other comprehensive income (loss) before reclassifications, net 75 (220) (13) (158) Amounts reclassified from accumulated other comprehensive income Amounts reclassified from accumulated other comprehensive income 2 — 70 72 Tax expense (1) — (18) (19) Amounts reclassified from accumulated other comprehensive income, net 1 — 52 53 Net current period other comprehensive income (loss) 76 (220) 39 (105) Balance at June 30, 2024 $ 78 $ (1,804) $ (2,752) $ (4,478) Change in Fair Value of Financial Instruments (1) Foreign Currency Translation Adjustments Postretirement Benefit Obligation (2) Total Balance at January 1, 2023 $ (11) $ (1,861) $ (2,751) $ (4,623) Other comprehensive income (loss) before reclassifications, net 7 228 (22) 213 Amounts reclassified from accumulated other comprehensive income Amounts reclassified from accumulated other comprehensive income 6 — 92 98 Tax expense (2) — (24) (26) Amounts reclassified from accumulated other comprehensive income, net 4 — 68 72 Net current period other comprehensive income (loss) 11 228 46 285 Balance at June 30, 2023 $ — $ (1,633) $ (2,705) $ (4,338) (1) Reclassifications from this category included in Accumulated other comprehensive loss are recorded in Total revenue, Interest expense, and Compensation and benefits in the Condensed Consolidated Statements of Income. Refer to Note 13 “Derivatives and Hedging” for further information regarding the Company’s derivative and hedging activity. (2) Reclassifications from this category included in Accumulated other comprehensive loss are recorded in Other income (expense) in the Condensed Consolidated Statements of Income.

Employee Benefits (Tables)

Employee Benefits (Tables)	6 Months Ended
Employee Benefits (Tables)	Jun. 30, 2024
Retirement Benefits [Abstract]
Schedule of Components of Net Periodic Benefit Cost for the Pension Plans	The following table provides the components of the net periodic (benefit) cost recognized in the Condensed Consolidated Statements of Income for Aon’s significant U.K., U.S., and other major pension plans, which are located in the Netherlands and Canada. Service cost is reported in Compensation and benefits and all other components are reported in Other income (expense) as follows (in millions): Three Months Ended June 30, U.K. U.S. Other 2024 2023 2024 2023 2024 2023 Service cost $ — $ — $ — $ — $ — $ — Interest cost 36 36 23 26 10 10 Expected return on plan assets, net of administration expenses (47) (48) (35) (30) (14) (12) Amortization of prior-service cost — 1 — — — — Amortization of net actuarial loss 21 19 8 8 3 4 Net periodic (benefit) cost 10 8 (4) 4 (1) 2 Loss on pension settlement — — — — — 27 Total net periodic (benefit) cost $ 10 $ 8 $ (4) $ 4 $ (1) $ 29 Six Months Ended June 30, U.K. U.S. Other 2024 2023 2024 2023 2024 2023 Service cost $ — $ — $ — $ — $ — $ — Interest cost 71 72 46 52 19 20 Expected return on plan assets, net of administration expenses (94) (94) (68) (60) (27) (24) Amortization of prior-service cost 1 1 — — — — Amortization of net actuarial loss 41 37 15 17 6 7 Net periodic (benefit) cost 19 16 (7) 9 (2) 3 Loss on pension settlement — — — — — 27 Total net periodic (benefit) cost $ 19 $ 16 $ (7) $ 9 $ (2) 30
Schedule of Employer's Contributions	The following table summarizes contributions made to the Company’s significant pension plans (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Contributions to U.K. pension plans $ 1 $ 1 $ 2 $ 2 Contributions to U.S. pension plans 4 5 18 21 Contributions to other major pension plans 5 2 7 8 Total contributions $ 10 $ 8 $ 27 $ 31

Derivatives and Hedging (Tables

Derivatives and Hedging (Tables)	6 Months Ended
Derivatives and Hedging (Tables)	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional and Fair Values of Derivative Instruments	The notional and fair values of derivative instruments are as follows (in millions): Notional Amount Net Amount of Derivative Assets Presented in the Statements of Financial Position (1) Net Amount of Derivative Liabilities Presented in the Statements of Financial Position (2) June 30, December 31, June 30, December 31, June 30, December 31, Foreign exchange contracts Accounted for as hedges $ 712 $ 1,724 $ 36 $ 34 $ — $ 2 Not accounted for as hedges (3) 492 382 — 2 1 1 Total $ 1,204 $ 2,106 $ 36 $ 36 $ 1 $ 3 (1) Included within Other current assets ($21 million at June 30, 2024 and $17 million at December 31, 2023) or Other non-current assets ($15 million at June 30, 2024 and $19 million at December 31, 2023). (2) Included within Other current liabilities ($1 million at June 30, 2024 and $3 million at December 31, 2023). (3) These contracts typically are for 90-day durations and executed close to the last day of the most recent reporting month, thereby resulting in nominal fair values at the balance sheet date.
Schedule of Derivative Gains (Losses)	The amounts of derivative gains recognized in the Condensed Consolidated Financial Statements are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Gain recognized in Accumulated other comprehensive loss $ 4 $ 9 $ 101 $ 9 The amounts of derivative gains (losses) reclassified from Accumulated other comprehensive loss to the Condensed Consolidated Statements of Income are as follows (in millions): Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Gain (loss) recognized in Total revenue $ 2 $ (1) $ (2) $ (6)

Fair Value Measurements and F_2

Fair Value Measurements and Financial Instruments (Tables)	6 Months Ended
Fair Value Measurements and Financial Instruments (Tables)	Jun. 30, 2024
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities That are Measured at Fair Value on a Recurring Basis	The following tables present the categorization of the Company’s assets and liabilities that are measured at fair value on a recurring basis at June 30, 2024 and December 31, 2023 (in millions): Fair Value Measurements Using Balance at June 30, 2024 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Money market funds (1) $ 2,983 $ 2,983 $ — $ — Other investments Government bonds $ 1 $ — $ 1 $ — Derivatives (2) Gross foreign exchange contracts $ 49 $ — $ 49 $ — Liabilities Derivatives (2) Gross foreign exchange contracts $ 15 $ — $ 15 $ — Fair Value Measurements Using Balance at December 31, 2023 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Money market funds (1) $ 3,204 $ 3,204 $ — $ — Other investments Government bonds $ 1 $ — $ 1 $ — Derivatives (2) Gross foreign exchange contracts $ 49 $ — $ 49 $ — Liabilities 0 Derivatives (2) Gross foreign exchange contracts $ 16 $ — $ 16 $ — (1) Included within Fiduciary assets or Short-term investments in the Condensed Consolidated Statements of Financial Position, depending on their nature and initial maturity. (2)
Schedule of Financial Instruments Where the Carrying Amounts and Fair Values Differ	The fair value of debt is classified as Level 2 of the fair value hierarchy. The following table provides the carrying value and fair value for the Company’s term debt (in millions): June 30, 2024 December 31, 2023 Carrying Value Fair Value Carrying Value Fair Value Current portion of long-term debt $ — $ — $ 600 $ 595 Long-term debt $ 17,610 $ 16,560 $ 9,995 $ 9,223

Accounting Principles and Pra_3

Accounting Principles and Practices (Details)	Jun. 30, 2024
Accounting Policies [Abstract]
VIE assets, percentage	1%

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Revenue [Line Items]
Total revenue	$ 3,760	$ 3,177	$ 7,830	$ 7,048
United States
Disaggregation of Revenue [Line Items]
Total revenue	1,837	1,427	3,349	2,922
Americas other than United States
Disaggregation of Revenue [Line Items]
Total revenue	362	308	685	609
United Kingdom
Disaggregation of Revenue [Line Items]
Total revenue	548	506	1,131	1,060
Ireland
Disaggregation of Revenue [Line Items]
Total revenue	35	28	68	58
Europe, Middle East, & Africa other than United Kingdom and Ireland
Disaggregation of Revenue [Line Items]
Total revenue	566	512	1,775	1,614
Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenue	412	396	822	785
Eliminations
Disaggregation of Revenue [Line Items]
Total revenue	(15)	(3)	(23)	(8)
Commercial Risk Solutions \| Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue	2,015	1,774	3,823	3,552
Reinsurance Solutions \| Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue	635	607	1,802	1,684
Health Solutions \| Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue	662	447	1,395	1,118
Wealth Solutions \| Operating Segments
Disaggregation of Revenue [Line Items]
Total revenue	$ 463	$ 352	$ 833	$ 702

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Schedule of Contract Assets Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Capitalized Cost To Fulfill Customer Contracts
Change in Capitalized Contract Costs
Balance at beginning of period	$ 269	$ 257	$ 370	$ 355
Additions	386	355	766	717
Amortization	(390)	(373)	(868)	(835)
Impairment	0	0	0	0
Foreign currency translation and other	(1)	3	(4)	5
Balance at end of period	264	242	264	242
Capitalized Cost To Obtain Customer Contracts
Change in Capitalized Contract Costs
Balance at beginning of period	194	183	195	185
Additions	18	13	32	23
Amortization	(14)	(13)	(27)	(25)
Impairment	0	0	0	0
Foreign currency translation and other	(2)	3	(4)	3
Balance at end of period	$ 196	$ 186	$ 196	$ 186

Accelerating Aon United Progr_3

Accelerating Aon United Program - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2024	Sep. 30, 2023	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Restructuring Cost and Reserve [Line Items]
Charges	$ 132		$ 0	$ 251	$ 0
Accelerating Aon United Program
Restructuring Cost and Reserve [Line Items]
Restructuring plan, period		3 years
Expected cost	1,000			1,000
Expected cost, cash charges	900			900
Expected cost, non-cash charges	100			100
Charges	$ 132			$ 251

Accelerating Aon United Progr_4

Accelerating Aon United Program - Schedule of Changes in the Company’s Liabilities for the Program (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Restructuring Reserve [Roll Forward]
Charges	$ 132	$ 0	$ 251	$ 0
Accelerating Aon United Program
Restructuring Reserve [Roll Forward]
Liability balance as of January 1, 2024			100
Charges	132		251
Cash payments			(98)
Foreign currency translation and other			(3)
Non-cash charges			(92)
Liability balance as of June 30, 2024	158		158
Total costs incurred from inception to date	386		386
Asset amortization	12		20
Accelerating Aon United Program \| Technology and other
Restructuring Reserve [Roll Forward]
Liability balance as of January 1, 2024			14
Charges			51
Cash payments			(29)
Foreign currency translation and other			0
Non-cash charges			(27)
Liability balance as of June 30, 2024	9		9
Total costs incurred from inception to date	65		65
Accelerating Aon United Program \| Workforce optimization
Restructuring Reserve [Roll Forward]
Liability balance as of January 1, 2024			86
Charges			145
Cash payments			(69)
Foreign currency translation and other			(3)
Non-cash charges			(10)
Liability balance as of June 30, 2024	149		149
Total costs incurred from inception to date	248		248
Accelerating Aon United Program \| Asset impairments
Restructuring Reserve [Roll Forward]
Liability balance as of January 1, 2024			0
Charges			55
Cash payments			0
Foreign currency translation and other			0
Non-cash charges			(55)
Liability balance as of June 30, 2024	0		0
Total costs incurred from inception to date	$ 73		$ 73

Cash and Cash Equivalents and_2

Cash and Cash Equivalents and Short-Term Investments (Details) £ in Millions, $ in Millions	Jun. 30, 2024 USD ($)	Jun. 30, 2024 GBP (£)	Dec. 31, 2023 USD ($)	Dec. 31, 2023 GBP (£)
Cash, Cash Equivalents, and Short-Term Investments [Abstract]
Cash and cash equivalents and short-term investments	$ 1,200		$ 1,100
Restricted cash and investments	116		120
Operating funds required to be held in U.K.	$ 69	£ 55	$ 80	£ 63

Other Financial Data - Schedule

Other Financial Data - Schedule of Other Income (Expense) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Other Financial Data [Abstract]
Gain from sales of businesses	$ 257		$ 0	$ 257	$ 0
Foreign currency remeasurement	5		(37)	9	(56)
Equity earnings	1		(1)	3	2
Pension and other postretirement	(11)		(43)	(21)	(60)
Extinguishment of debt	(6)		0	(6)	0
Financial instruments and other	(10)		22	69	30
Total	$ 236		$ (59)	$ 311	$ (84)
Deferred consideration on divestiture		$ 82

Other Financial Data - Schedu_2

Other Financial Data - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Movement ofAccounts Receivable, Allowance for Credit Loss, Current [Roll Forward]
Balance at beginning of period	$ 81	$ 83	$ 79	$ 76
Provision	6	2	11	9
Accounts written off, net of recoveries	0	(3)	(2)	(3)
Foreign currency translation and other	0	1	(1)	1
Balance at end of period	$ 87	$ 83	$ 87	$ 83

Other Financial Data - Schedu_3

Other Financial Data - Schedule of Other Current Assets (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Other Financial Data [Abstract]
Assets held for sale	$ 359	$ 354
Cost to fulfill contracts with customers	264	370
Prepaid expenses	176	100
Taxes receivable	37	35
Other	227	137
Total	$ 1,063	$ 996

Other Financial Data - Schedu_4

Other Financial Data - Schedule of Other Non-current Assets (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Other Financial Data [Abstract]
Cost to obtain contracts with customers	$ 196	$ 195
Taxes receivable	92	100
Investments	83	45
Leases	17	26
Other	241	140
Total	$ 629	$ 506

Other Financial Data - Schedu_5

Other Financial Data - Schedule of Other Current Liabilities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Other Financial Data [Abstract]
Deferred revenue	$ 391		$ 391		$ 270
Taxes payable	337		337		291
Leases	203		203		182
Contingent consideration	106		106		0
Liabilities held for sale	64		64		69
Other	1,209		1,209		1,066
Total	2,310		2,310		$ 1,878
Revenue recognized from deferred revenue	$ 199	$ 169	$ 378	$ 336

Other Financial Data - Schedu_6

Other Financial Data - Schedule of Other Non-current Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Other Financial Data [Abstract]
Taxes payable	$ 848	$ 827
Contingent consideration	91	0
Compensation and benefits	59	59
Deferred revenue	34	33
Leases	0	10
Other	103	145
Total	$ 1,135	1,074
Noncurrent portion of transition tax		$ 72

Acquisitions and Dispositions_3

Acquisitions and Dispositions of Businesses - Narrative (Details) shares in Millions

3 Months Ended

6 Months Ended

Apr. 25, 2024 USD ($) employee shares

Mar. 31, 2024 USD ($)

Jun. 30, 2024 USD ($) acquisition

Jun. 30, 2023 acquisition

Jun. 30, 2024 USD ($) acquisition

Jun. 30, 2023 acquisition

Jun. 18, 2024

Jun. 13, 2024

May 31, 2024

May 02, 2024

Apr. 26, 2024

Apr. 03, 2024

Dec. 31, 2023 USD ($)

Nov. 30, 2023

Aug. 30, 2023

Jun. 22, 2023

Business Acquisition [Line Items]

Number of business acquired under business combination | acquisition

Issuance of debt

$ 6,000,000,000

Proceeds from long-term lines of credit

$ 2,000,000,000

Goodwill

$ 15,281,000,000

$ 8,414,000,000

Intangible assets, net

6,794,000,000

$ 234,000,000

Extinguishment of debt

6,000,000

NFP Acquisition

Business Acquisition [Line Items]

Number of colleagues (more than) | employee

7,700

Southern Insurance Agency, L.L.C.,

Business Acquisition [Line Items]

Percentage of capital acquired

100%

Sean Barrett Bloodstock Insurance Limited,

Business Acquisition [Line Items]

Percentage of capital acquired

100%

Walden Wealth Partners LLC.,

Business Acquisition [Line Items]

Percentage of capital acquired

100%

Morley Agency, Inc.,

Business Acquisition [Line Items]

Percentage of capital acquired

100%

Honest Employment Law Practice Ltd.,

Business Acquisition [Line Items]

Percentage of capital acquired

100%

Novabrok

Business Acquisition [Line Items]

Percentage of capital acquired

100%

NFP Acquisition

Business Acquisition [Line Items]

Percentage of capital acquired

100%

Total consideration

$ 9,100,000,000

9,129,000,000

Cash

$ 3,200,000,000

3,247,000,000

Number of shares issued for acquisition (up to) | shares

Equity interest issued or issuable, value

$ 5,900,000,000

Goodwill

6,953,000,000

$ 6,953,000,000

Weighted average useful life

19 years

Intangible assets, net

6,500,000,000

$ 6,500,000,000

Acquisition related costs

$ 79,000,000

$ 90,000,000

NFP Acquisition | Customer Relationships

Business Acquisition [Line Items]

Weighted average useful life

20 years

NFP Acquisition | Tradenames

Business Acquisition [Line Items]

Weighted average useful life

10 years

NFP Acquisition | Technology and other

Business Acquisition [Line Items]

Weighted average useful life

7 years

Global Insurance Brokers

Business Acquisition [Line Items]

Percentage of capital acquired

100%

Gi&Bi S.r.l

Business Acquisition [Line Items]

Percentage of capital acquired

100%

N. Goddard Seguros

Business Acquisition [Line Items]

Percentage of capital acquired

100%

2023 Acquisitions

Business Acquisition [Line Items]

Percentage of capital acquired

100%

Acquisitions and Dispositions_4

Acquisitions and Dispositions of Businesses - Schedule of Consideration Transferred and Preliminary Value of Intangible Assets (Details) - USD ($) $ in Millions		6 Months Ended
	Apr. 25, 2024	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Assets acquired:
Goodwill		$ 15,281	$ 8,414
Liabilities assumed:
Funds held on behalf of clients		7,309		$ 7,538
2024 Acquisition
Consideration transferred:
Cash		3,356
Deferred and contingent consideration		7
Class A ordinary shares issued		5,882
Aggregate consideration transferred		9,245
Assets acquired:
Cash and cash equivalents		296
Receivables		324
Fiduciary assets		417
Goodwill		7,022
Other intangible assets:
Operating lease right-of-use assets		145
Current assets		113
Non-current assets		170
Total assets acquired		15,188
Liabilities assumed:
Accounts payable and accrued liabilities		291
Fiduciary liabilities		417
Current liabilities		227
Long-term debt		3,422
Non-current operating lease liabilities		127
Deferred tax liabilities		1,129
Non-current liabilities		142
Total liabilities assumed		5,755
Less: Fair value of redeemable noncontrolling interests		(103)
Less: Fair value of nonredeemable noncontrolling interests		(85)
Net assets acquired		9,245
Funds held on behalf of clients		283
2024 Acquisition \| Customer-related and contract-based
Other intangible assets:
Intangible assets		5,875
2024 Acquisition \| Tradenames
Other intangible assets:
Intangible assets		800
2024 Acquisition \| Technology and other
Other intangible assets:
Intangible assets		26
NFP Acquisition
Consideration transferred:
Cash	$ 3,200	3,247
Deferred and contingent consideration		0
Class A ordinary shares issued		5,882
Aggregate consideration transferred	$ 9,100	9,129
Assets acquired:
Cash and cash equivalents		293
Receivables		321
Fiduciary assets		411
Goodwill		6,953
Other intangible assets:
Operating lease right-of-use assets		143
Current assets		110
Non-current assets		169
Total assets acquired		15,050
Liabilities assumed:
Accounts payable and accrued liabilities		283
Fiduciary liabilities		411
Current liabilities		227
Long-term debt		3,422
Non-current operating lease liabilities		125
Deferred tax liabilities		1,123
Non-current liabilities		142
Total liabilities assumed		5,733
Less: Fair value of redeemable noncontrolling interests		(103)
Less: Fair value of nonredeemable noncontrolling interests		(85)
Net assets acquired		9,129
NFP Acquisition \| Customer-related and contract-based
Other intangible assets:
Intangible assets		5,825
NFP Acquisition \| Tradenames
Other intangible assets:
Intangible assets		800
NFP Acquisition \| Technology and other
Other intangible assets:
Intangible assets		25
Other Acquisitions
Consideration transferred:
Cash		109
Deferred and contingent consideration		7
Class A ordinary shares issued		0
Aggregate consideration transferred		116
Assets acquired:
Cash and cash equivalents		3
Receivables		3
Fiduciary assets		6
Goodwill		69
Other intangible assets:
Operating lease right-of-use assets		2
Current assets		3
Non-current assets		1
Total assets acquired		138
Liabilities assumed:
Accounts payable and accrued liabilities		8
Fiduciary liabilities		6
Current liabilities		0
Long-term debt		0
Non-current operating lease liabilities		2
Deferred tax liabilities		6
Non-current liabilities		0
Total liabilities assumed		22
Less: Fair value of redeemable noncontrolling interests		0
Less: Fair value of nonredeemable noncontrolling interests		0
Net assets acquired		116
Other Acquisitions \| Customer-related and contract-based
Other intangible assets:
Intangible assets		50
Other Acquisitions \| Tradenames
Other intangible assets:
Intangible assets		0
Other Acquisitions \| Technology and other
Other intangible assets:
Intangible assets		$ 1

Acquisitions and Dispositions_5

Acquisitions and Dispositions of Businesses - Schedule of Revenue and Earnings Acquired (Details) - NFP Acquisition $ in Millions	3 Months Ended
	Jun. 30, 2024 USD ($)
Business Acquisition [Line Items]
Revenue	$ 442
Net loss attributable to Aon shareholders	$ (19)

Acquisitions and Dispositions_6

Acquisitions and Dispositions of Businesses - Schedule of Pro Forma Information (Details) - NFP Acquisition - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenue	$ 3,910	$ 3,729	$ 8,528	$ 8,099
Net income attributable to Aon shareholders	$ 465	$ 424	$ 1,396	$ 1,266

Acquisitions and Dispositions_7

Acquisitions and Dispositions of Businesses - Completed Dispositions (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($) disposition	Jun. 30, 2023 USD ($) disposition	Jun. 30, 2024 USD ($) disposition	Jun. 30, 2023 USD ($) disposition	Dec. 31, 2023 USD ($)
Business Combination, Asset Acquisition, and Joint Venture Formation [Abstract]
Number of dispositions \| disposition	2	0	3	0
Gain on disposition of business	$ 257	$ 0	$ 257	$ 0
Loss on disposition of business	2	$ 0	2	$ 0
Assets held for sale	359		359		$ 354
Liabilities held for sale	64		64		$ 69
Intangibles assets held for sale	$ 156		$ 156

Acquisitions and Dispositions_8

Acquisitions and Dispositions of Businesses - Other Significant Activity (Details) - May 1, 2017 Divested Business - Disposal Group, Disposed of by Sale, Not Discontinued Operations - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	May 01, 2017
Dispositions
Purchase price		$ 4,300
Deferred consideration		$ 500
Proceeds from divestiture of businesses	$ 82

Goodwill and Other Intangible_3

Goodwill and Other Intangible Assets - Schedule of Changes in the Net Carrying Amount of Goodwill (Details) $ in Millions	6 Months Ended
	Jun. 30, 2024 USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 8,414
Goodwill related to current year acquisitions	7,022
Goodwill related to current year disposals	(35)
Foreign currency translation and other	(120)
Ending balance	$ 15,281

Goodwill and Other Intangible_4

Goodwill and Other Intangible Assets - Schedule of Other Intangible Assets by Asset Class (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 8,917	$ 2,244
Accumulated Amortization and Impairment	2,123	2,010
Total	6,794	234
Customer-related and contract-based
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,729	1,873
Accumulated Amortization and Impairment	1,784	1,686
Total	5,945	187
Tradenames
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	812	12
Accumulated Amortization and Impairment	26	12
Intangible assets, net	786	0
Technology and other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	376	359
Accumulated Amortization and Impairment	313	312
Total	$ 63	$ 47

Goodwill and Other Intangible_5

Goodwill and Other Intangible Assets - Schedule of Estimated Future Amortization Expense on Intangible Assets (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2024	$ 348
2025	737
2026	661
2027	602
2028	550
2029	507
Thereafter	3,389
Total	$ 6,794	$ 234

Debt - Narrative (Details)

Debt - Narrative (Details)			3 Months Ended	6 Months Ended
Debt - Narrative (Details)	May 28, 2024 USD ($)	Apr. 25, 2024 USD ($)	Jun. 30, 2024 USD ($) credit_facility	Jun. 30, 2024 USD ($) credit_facility	Jun. 30, 2024 EUR (€) credit_facility	Apr. 02, 2024 USD ($)	Mar. 01, 2024 USD ($)	Dec. 31, 2023 USD ($)	Nov. 30, 2023 USD ($)	Feb. 28, 2023 USD ($)
Debt Instrument [Line Items]
Proceeds from long-term lines of credit		$ 2,000,000,000
Extinguishment of debt			$ 6,000,000	$ 6,000,000
Number of credit facilities \| credit_facility			2	2	2
Borrowings under credit facilities			$ 0	$ 0				$ 0
Senior Notes
Debt Instrument [Line Items]
Debt, face amount							$ 6,000,000,000
Line of Credit
Debt Instrument [Line Items]
Debt instrument, repurchased face amount						$ 3,300,000,000
Line of credit facility, available credit			2,000,000,000	2,000,000,000
Line of Credit \| Delayed Draw Term Loan
Debt Instrument [Line Items]
Proceeds from long-term lines of credit		$ 2,000,000,000
Repayments of long-term lines of credit	$ 300,000,000
Line of Credit \| Credit Facility Expiring September 2027
Debt Instrument [Line Items]
Maximum borrowing capacity			1,000,000,000	1,000,000,000
Line of Credit \| Credit Facility Expiring October 2028
Debt Instrument [Line Items]
Maximum borrowing capacity			1,000,000,000	1,000,000,000
3.50% Senior Notes Due June 2024 \| Senior Notes
Debt Instrument [Line Items]
Debt, face amount			$ 600,000,000	$ 600,000,000
Debt interest rate percentage			3.50%	3.50%	3.50%
6.875% Senior Notes Due 2028 \| Senior Notes \| NFP
Debt Instrument [Line Items]
Debt interest rate percentage						6.875%
4.875% Senior Notes Due 2028 \| Senior Notes \| NFP
Debt Instrument [Line Items]
Debt interest rate percentage						4.875%
7.500% Senior Secured Notes Due 2030 \| Senior Notes \| NFP
Debt Instrument [Line Items]
Debt interest rate percentage						7.50%
8.500% Senior Secured Notes Due 2031 \| Senior Notes \| NFP
Debt Instrument [Line Items]
Debt interest rate percentage						8.50%
5.125% Senior Notes Due March 2027 \| Senior Notes
Debt Instrument [Line Items]
Debt, face amount							$ 600,000,000
Debt interest rate percentage							5.125%
5.150% Senior Notes Due March 2029 \| Senior Notes
Debt Instrument [Line Items]
Debt, face amount							$ 1,000,000,000
Debt interest rate percentage							5.15%
5.300% Senior Notes Due March 2031 \| Senior Notes
Debt Instrument [Line Items]
Debt, face amount							$ 650,000,000
Debt interest rate percentage							5.30%
5.450% Senior Notes Due March 2034 \| Senior Notes
Debt Instrument [Line Items]
Debt, face amount							$ 1,750,000,000
Debt interest rate percentage							5.45%
5.750% Senior Notes Due March 2054 \| Senior Notes
Debt Instrument [Line Items]
Debt, face amount							$ 2,000,000,000
Debt interest rate percentage							5.75%
4.00% Senior Notes Due November 2023 \| Senior Notes
Debt Instrument [Line Items]
Debt, face amount									$ 350,000,000
Debt interest rate percentage									4%
5.350% Senior Notes Due February 2033 \| Senior Notes
Debt Instrument [Line Items]
Debt, face amount										$ 750,000,000
Debt interest rate percentage										5.35%
U.S. Program \| Commercial paper outstanding
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 1,300,000,000	$ 1,300,000,000
European Program \| Commercial paper outstanding
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 668,000,000	$ 668,000,000	€ 625,000,000

Debt - Schedule of Commercial P

Debt - Schedule of Commercial Paper Outstanding (Details) - Commercial paper outstanding - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Debt Instrument [Line Items]
Commercial paper outstanding	$ 0		$ 0		$ 597
Weighted average commercial paper outstanding	$ 34	$ 435	$ 207	$ 414
Weighted average interest rate of commercial paper outstanding	5.50%	4.90%	5.63%	4.18%

Income Taxes (Details)

Income Taxes (Details)	3 Months Ended		6 Months Ended
Income Taxes (Details)	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Tax Disclosure [Abstract]
Effective income tax rate	22.90%	12.60%	23.10%	17.30%

Shareholders' Equity (Deficit_2

Shareholders' Equity (Deficit) - Narrative (Details) - USD ($) shares in Millions	1 Months Ended				3 Months Ended		6 Months Ended		147 Months Ended
	Feb. 28, 2022	Nov. 30, 2020	Jun. 30, 2017	Nov. 30, 2014	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Apr. 30, 2012
Equity [Abstract]
Share repurchase authorization amount					$ 27,500,000,000		$ 27,500,000,000		$ 27,500,000,000	$ 5,000,000,000
Share repurchase authorization amount, increase during period	$ 7,500,000,000	$ 5,000,000,000	$ 5,000,000,000	$ 5,000,000,000
Share repurchase, remaining authorized repurchase amount					$ 2,800,000,000		$ 2,800,000,000		$ 2,800,000,000
Shares purchased (in shares)					0.8	1.7	1.6	3.5	170.7
Total cost of shares purchased					$ 250,000,000	$ 550,000,000	$ 500,000,000	$ 1,100,000,000	$ 24,700,000,000
Antidilutive securities excluded from computation of earnings per share (in shares)					1.4	0	0.6	0

Shareholders' Equity (Deficit_3

Shareholders' Equity (Deficit) - Schedule of Share Repurchases (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended		147 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024
Equity [Abstract]
Shares repurchased (in shares)	0.8	1.7	1.6	3.5	170.7
Average price per share (in dollars per share)	$ 298.09	$ 323.96	$ 304.20	$ 314.36
Repurchase costs recorded to accumulated deficit	$ 250	$ 550	$ 500	$ 1,100	$ 24,700

Shareholders' Equity (Deficit_4

Shareholders' Equity (Deficit) - Schedule of Components of Weighted Average Ordinary Shares Outstanding (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Equity [Abstract]
Basic weighted average ordinary shares outstanding (in shares)	212.5	204.7	205.8	205.4
Dilutive effect of potentially issuable shares (in shares)	0.8	1.6	0.9	1.3
Diluted weighted average ordinary shares outstanding (in shares)	213.3	206.3	206.7	206.7

Shareholders' Equity (Deficit_5

Shareholders' Equity (Deficit) - Schedule of Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ (28)	$ 58	$ (742)	$ (429)
Other comprehensive income (loss) before reclassifications, net			(158)	213
Amounts reclassified from accumulated other comprehensive income
Amounts reclassified from accumulated other comprehensive income			72	98
Tax expense			(19)	(26)
Amounts reclassified from accumulated other comprehensive income, net			53	72
Total other comprehensive income (loss)	(74)	206	(105)	285
Ending balance	6,028	162	6,028	162
AOCI Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(4,404)	(4,544)	(4,373)	(4,623)
Amounts reclassified from accumulated other comprehensive income
Ending balance	(4,478)	(4,338)	(4,478)	(4,338)
Change in Fair Value of Financial Instruments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			2	(11)
Other comprehensive income (loss) before reclassifications, net			75	7
Amounts reclassified from accumulated other comprehensive income
Amounts reclassified from accumulated other comprehensive income			2	6
Tax expense			(1)	(2)
Amounts reclassified from accumulated other comprehensive income, net			1	4
Total other comprehensive income (loss)			76	11
Ending balance	78	0	78	0
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			(1,584)	(1,861)
Other comprehensive income (loss) before reclassifications, net			(220)	228
Amounts reclassified from accumulated other comprehensive income
Amounts reclassified from accumulated other comprehensive income			0	0
Tax expense			0	0
Amounts reclassified from accumulated other comprehensive income, net			0	0
Total other comprehensive income (loss)			(220)	228
Ending balance	(1,804)	(1,633)	(1,804)	(1,633)
Postretirement Benefit Obligation
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			(2,791)	(2,751)
Other comprehensive income (loss) before reclassifications, net			(13)	(22)
Amounts reclassified from accumulated other comprehensive income
Amounts reclassified from accumulated other comprehensive income			70	92
Tax expense			(18)	(24)
Amounts reclassified from accumulated other comprehensive income, net			52	68
Total other comprehensive income (loss)			39	46
Ending balance	$ (2,752)	$ (2,705)	$ (2,752)	$ (2,705)

Employee Benefits - Schedule of

Employee Benefits - Schedule of Components of Net Periodic (Benefit) Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
U.K.
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	36	36	71	72
Expected return on plan assets, net of administration expenses	(47)	(48)	(94)	(94)
Amortization of prior-service cost	0	1	1	1
Amortization of net actuarial loss	21	19	41	37
Net periodic (benefit) cost	10	8	19	16
Loss on pension settlement	0	0	0	0
Total net periodic (benefit) cost	10	8	19	16
Other
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0
Interest cost	10	10	19	20
Expected return on plan assets, net of administration expenses	(14)	(12)	(27)	(24)
Amortization of prior-service cost	0	0	0	0
Amortization of net actuarial loss	3	4	6	7
Net periodic (benefit) cost	(1)	2	(2)	3
Loss on pension settlement	0	27	0	27
Total net periodic (benefit) cost	(1)	29	(2)	30
U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0	0	0
Interest cost	23	26	46	52
Expected return on plan assets, net of administration expenses	(35)	(30)	(68)	(60)
Amortization of prior-service cost	0	0	0	0
Amortization of net actuarial loss	8	8	15	17
Net periodic (benefit) cost	(4)	4	(7)	9
Loss on pension settlement	0	0	0	0
Total net periodic (benefit) cost	$ (4)	$ 4	$ (7)	$ 9

Employee Benefits - Narrative (

Employee Benefits - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
U.K.
Defined Benefit Plan Disclosure [Line Items]
Non-cash settlement charge	$ 0	$ 0	$ 0	$ 0
Expected future employer cash contribution	2		2
Other
Defined Benefit Plan Disclosure [Line Items]
Non-cash settlement charge	0	27	0	27
Expected future employer cash contribution	13		13
U.S.
Defined Benefit Plan Disclosure [Line Items]
Non-cash settlement charge	0	$ 0	0	$ 0
Expected future employer cash contribution	$ 53		$ 53

Employee Benefits - Schedule _2

Employee Benefits - Schedule of Employer Contributions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 10	$ 8	$ 27	$ 31
U.K.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	1	1	2	2
Other
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	5	2	7	8
U.S.
Defined Benefit Plan Disclosure [Line Items]
Company’s benefit pension plans	$ 4	$ 5	$ 18	$ 21

Derivatives and Hedging - Narra

Derivatives and Hedging - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Foreign exchange contracts
Derivative [Line Items]
Pretax gains that will be reclassified into earnings in the next twelve months			$ 6
Not designated as hedging instrument \| Foreign exchange contracts
Derivative [Line Items]
Term of derivative contract			90 days
Gain (loss) on derivative	$ (6)	$ 28	$ (9)	$ 37
Not designated as hedging instrument \| Foreign exchange contracts \| Maximum
Derivative [Line Items]
Term of derivative contract			1 year
Cash Flow Hedging
Derivative [Line Items]
Foreign currency exposures, maximum average hedging period (less than) (in years)			2 years

Derivatives and Hedging - Sched

Derivatives and Hedging - Schedule of Notional and Fair Values of Derivative Instruments (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
Other Current Assets
Derivative [Line Items]
Net amount of derivative assets	$ 21	$ 17
Other Noncurrent Assets
Derivative [Line Items]
Net amount of derivative assets	15	19
Other Current Liabilities
Derivative [Line Items]
Net amount of derivative liabilities	1	3
Foreign exchange contracts
Derivative [Line Items]
Notional Amount	1,204	2,106
Net amount of derivative assets	36	36
Net amount of derivative liabilities	1	3
Accounted for as hedges \| Foreign exchange contracts
Derivative [Line Items]
Notional Amount	712	1,724
Net amount of derivative assets	36	34
Net amount of derivative liabilities	0	2
Not accounted for as hedges \| Foreign exchange contracts
Derivative [Line Items]
Notional Amount	492	382
Net amount of derivative assets	0	2
Net amount of derivative liabilities	$ 1	$ 1
Term of derivative contract	90 days

Derivatives and Hedging - Sch_2

Derivatives and Hedging - Schedule of Derivative Gains (Losses) Recognized in the Consolidated Financial Statements (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gain recognized in Accumulated other comprehensive loss	$ 4	$ 9	$ 101	$ 9
Gain (loss) recognized in Total revenue	$ 2	$ (1)	$ (2)	$ (6)

Fair Value Measurements and F_3

Fair Value Measurements and Financial Instruments - Schedule of Assets and Liabilities that are Measured at Fair Value on a Recurring Basis (Details) - Recurring - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Money market funds
Assets
Money market funds	$ 2,983	$ 3,204
Government bonds
Assets
Other investments	1	1
Gross foreign exchange contracts
Assets
Derivatives	49	49
Liabilities
Derivatives	15	16
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Money market funds
Assets
Money market funds	2,983	3,204
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Government bonds
Assets
Other investments	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Gross foreign exchange contracts
Assets
Derivatives	0	0
Liabilities
Derivatives	0	0
Significant Other Observable Inputs (Level 2) \| Money market funds
Assets
Money market funds	0	0
Significant Other Observable Inputs (Level 2) \| Government bonds
Assets
Other investments	1	1
Significant Other Observable Inputs (Level 2) \| Gross foreign exchange contracts
Assets
Derivatives	49	49
Liabilities
Derivatives	15	16
Significant Unobservable Inputs (Level 3) \| Money market funds
Assets
Money market funds	0	0
Significant Unobservable Inputs (Level 3) \| Government bonds
Assets
Other investments	0	0
Significant Unobservable Inputs (Level 3) \| Gross foreign exchange contracts
Assets
Derivatives	0	0
Liabilities
Derivatives	$ 0	$ 0

Fair Value Measurements and F_4

Fair Value Measurements and Financial Instruments - Schedule of Financial Instruments where the Carrying Amounts and Fair Values Differ (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 17,610	$ 9,995
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current portion of long-term debt	0	600
Long-term debt	17,610	9,995
Fair Value \| Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current portion of long-term debt, fair value	0	595
Long term debt, fair value	$ 16,560	$ 9,223

Claims, Lawsuits, and Other C_2

Claims, Lawsuits, and Other Contingencies - Legal Narrative (Details) - Fatal Plain Crash In November 2016 £ in Millions, $ in Millions		1 Months Ended						3 Months Ended
	Jun. 30, 2024 USD ($)	Feb. 29, 2024 plaintiff	Dec. 31, 2022 plaintiff	Apr. 30, 2021 GBP (£) plaintiff	Aug. 31, 2020 USD ($) plaintiff	Nov. 30, 2019 USD ($) defendant	Nov. 30, 2018 USD ($)	Dec. 31, 2023 USD ($)
Pending Litigation
Legal, Guarantees and Indemnifications
Damages sought	$ 37			£ 29	$ 844		$ 16
Number of defendants \| defendant						3
Damages sought option 1						$ 300
Damages sought option 2						50
Damages sought option 3						$ 25
Number of plaintiffs \| plaintiff			43	16	43
Litigation settlement expense								$ 197
Settled Litigation
Legal, Guarantees and Indemnifications
Number of plaintiffs \| plaintiff		16

Claims, Lawsuits, and Other C_3

Claims, Lawsuits, and Other Contingencies - Letters of Credit Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Letters of credit outstanding	$ 145	$ 86

Claims, Lawsuits, and Other C_4

Claims, Lawsuits, and Other Contingencies - Premium Payments (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Maximum potential funding under commitments	$ 138	$ 194

Segment Information (Details)

Segment Information (Details)	6 Months Ended
Segment Information (Details)	Jun. 30, 2024 performance_metric segment revenue_line
Segment Reporting [Abstract]
Number of reportable segment \| segment	1
Number of solution lines \| revenue_line	4
Number of performance metrics \| performance_metric	4