Affiliated Managers (MGR) 10-Q7 Nov 242024 Q3 Quarterly reportFinancial data

Company Profile

Cover Page

Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2024	Nov. 05, 2024
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2024
Document Transition Report	false
Entity File Number	001-13459
Entity Registrant Name	AFFILIATED MANAGERS GROUP, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3218510
Entity Address, Address Line One	777 South Flagler Drive
Entity Address, City or Town	West Palm Beach
Entity Address, State or Province	FL
Entity Address, Postal Zip Code	33401
City Area Code	800
Local Phone Number	345-1100
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		30,225,132
Entity Central Index Key	0001004434
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Common Stock ($0.01 par value)
Document Information [Line Items]
Title of 12(b) Security	Common Stock ($0.01 par value)
Trading Symbol	AMG
Security Exchange Name	NYSE
5.875% Junior Subordinated Notes due 2059
Document Information [Line Items]
Title of 12(b) Security	5.875% Junior Subordinated Notes due 2059
Trading Symbol	MGR
Security Exchange Name	NYSE
4.750% Junior Subordinated Notes due 2060
Document Information [Line Items]
Title of 12(b) Security	4.750% Junior Subordinated Notes due 2060
Trading Symbol	MGRB
Security Exchange Name	NYSE
4.200% Junior Subordinated Notes due 2061
Document Information [Line Items]
Title of 12(b) Security	4.200% Junior Subordinated Notes due 2061
Trading Symbol	MGRD
Security Exchange Name	NYSE
6.750% Junior Subordinated Notes due 2064
Document Information [Line Items]
Title of 12(b) Security	6.750% Junior Subordinated Notes due 2064
Trading Symbol	MGRE
Security Exchange Name	NYSE

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Statement [Abstract]
Consolidated revenue	$ 516.4	$ 525.2	$ 1,516.6	$ 1,555.2
Consolidated expenses:
Compensation and related expenses	220.8	211.8	676.5	663
Selling, general and administrative	97	91.1	278.1	273.4
Intangible amortization and impairments	7.3	12.5	21.8	37.5
Interest expense	34.7	31.1	98.1	92.4
Depreciation and other amortization	3.3	3	9.4	10
Other expenses (net)	11.6	7.9	31.5	36.2
Total consolidated expenses	374.7	357.4	1,115.4	1,112.5
Equity method income (net)	52.6	39.8	188.3	154.3
Affiliate Transaction gain	0	133.1	0	133.1
Investment and other income	22.8	23	60	87.2
Income before income taxes	217.1	363.7	649.5	817.3
Income tax expense	31.3	77.7	130	155.4
Net income	185.8	286	519.5	661.9
Net income (non-controlling interests)	(62.2)	(69)	(170)	(185.1)
Net income (controlling interest)	$ 123.6	$ 217	$ 349.5	$ 476.8
Average shares outstanding (basic) (in shares)	30.1	34.9	31.4	35.6
Average shares outstanding (diluted) (in shares)	35	43.4	35.2	42.9
Earnings per share (basic) (in dollars per share)	$ 4.11	$ 6.22	$ 11.11	$ 13.41
Earnings per share (diluted) (in dollars per share)	$ 3.78	$ 5.48	$ 10.25	$ 12.28

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 185.8	$ 286	$ 519.5	$ 661.9
Other comprehensive income (loss), net of tax:
Foreign currency translation gain (loss)	39.2	(30.6)	42.6	20.6
Change in net realized and unrealized gain (loss) on derivative financial instruments	1	(0.3)	1.4	0.5
Change in net unrealized gain (loss) on available-for-sale debt securities	0	0.6	0.4	0.4
Other comprehensive income (loss), net of tax	40.2	(30.3)	44.4	21.5
Comprehensive income	226	255.7	563.9	683.4
Comprehensive income (non-controlling interests)	(77.9)	(57.4)	(186)	(183.1)
Comprehensive income (controlling interest)	$ 148.1	$ 198.3	$ 377.9	$ 500.3

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Assets
Cash and cash equivalents	$ 1,010.7	$ 813.6
Receivables	457.1	368.4
Investments in marketable securities	66.1	461
Goodwill	2,532	2,523.6
Acquired client relationships (net)	1,807.1	1,812.4
Equity method investments in Affiliates (net)	2,148.4	2,288.5
Fixed assets (net)	61	67.3
Other investments	532.8	480.9
Other assets	287.8	243.9
Total assets	8,903	9,059.6
Liabilities and Equity
Payables and accrued liabilities	625.7	628.5
Debt	2,619.7	2,537.5
Deferred income tax liability (net)	522	463.8
Other liabilities	464.5	466.3
Total liabilities	4,231.9	4,096.1
Commitments and contingencies (Note 8)
Redeemable non-controlling interests	397.1	393.4
Equity:
Common stock ($0.01 par value, 153.0 shares authorized; 58.5 shares issued as of December 31, 2023 and September 30, 2024)	0.6	0.6
Additional paid-in capital	711.3	741.4
Accumulated other comprehensive loss	(139.2)	(167.6)
Retained earnings	6,738.1	6,389.6
Total stockholders' equity before treasury stock	7,310.8	6,964
Less: Treasury stock, at cost (25.3 shares and 28.4 shares as of December 31, 2023 and September 30, 2024, respectively)	(3,994.5)	(3,376.1)
Total stockholders' equity	3,316.3	3,587.9
Non-controlling interests	957.7	982.2
Total equity	4,274	4,570.1
Total liabilities and equity	$ 8,903	$ 9,059.6

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares shares in Millions	Sep. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	153	153
Common stock, shares issued (in shares)	58.5	58.5
Treasury stock, at cost (in shares)	28.4	25.3

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Treasury Stock at Cost	Non- controlling Interests
Beginning balance at Dec. 31, 2022	$ 4,175.6	$ 0.6	$ 695.5	$ (203.4)	$ 5,718.2	$ (2,980.6)	$ 945.3
Increase (Decrease) in Stockholders' Equity
Net income	661.9				476.8		185.1
Other comprehensive income (loss), net of tax	21.5			23.5			(2)
Share-based compensation	43.9		43.9
Common stock issued under share-based incentive plans	(31.3)		(47.2)			15.9
Share repurchases	(218)		59.1			(277.1)
Dividends	(1.2)				(1.2)
Affiliate equity activity:
Affiliate equity compensation	41.1		7.7				33.4
Issuances	16.3		(13.3)				29.6
Purchases	3.8		6.7				(2.9)
Changes in redemption value of Redeemable non-controlling interests	(46.9)		(46.9)
Transfers to Redeemable non-controlling interests	(0.1)						(0.1)
Capital contributions and other	14.4						14.4
Distributions to non-controlling interests	(216.4)						(216.4)
Effect of deconsolidation of Affiliates	(0.4)		16.8				(17.2)
Ending balance at Sep. 30, 2023	4,464.2	0.6	722.3	(179.9)	6,193.8	(3,241.8)	969.2
Beginning balance at Jun. 30, 2023	4,368.4	0.6	651.9	(161.2)	5,977.2	(3,070.5)	970.4
Increase (Decrease) in Stockholders' Equity
Net income	286				217		69
Other comprehensive income (loss), net of tax	(30.3)			(18.7)			(11.6)
Share-based compensation	14.5		14.5
Common stock issued under share-based incentive plans	(6.1)		(7.9)			1.8
Share repurchases	(173.1)					(173.1)
Dividends	(0.4)				(0.4)
Affiliate equity activity:
Affiliate equity compensation	12.5		1				11.5
Issuances	1.6		(5)				6.6
Purchases	(0.6)		0.7				(1.3)
Changes in redemption value of Redeemable non-controlling interests	50.3		50.3
Capital contributions and other	1.8						1.8
Distributions to non-controlling interests	(60)						(60)
Effect of deconsolidation of Affiliates	(0.4)		16.8				(17.2)
Ending balance at Sep. 30, 2023	4,464.2	0.6	722.3	(179.9)	6,193.8	(3,241.8)	969.2
Beginning balance at Dec. 31, 2023	4,570.1	0.6	741.4	(167.6)	6,389.6	(3,376.1)	982.2
Increase (Decrease) in Stockholders' Equity
Net income	519.5				349.5		170
Other comprehensive income (loss), net of tax	44.4			28.4			16
Share-based compensation	42.1		42.1
Common stock issued under share-based incentive plans	(77)		(43.5)			(33.5)
Share repurchases	(584.9)					(584.9)
Dividends	(1)				(1)
Affiliate equity activity:
Affiliate equity compensation	42.6		11.7				30.9
Issuances	7.5		(3.8)				11.3
Purchases	(14.8)		6.1				(20.9)
Changes in redemption value of Redeemable non-controlling interests	(42.7)		(42.7)
Transfers to Redeemable non-controlling interests	(1.7)						(1.7)
Capital contributions and other	(23.6)						(23.6)
Distributions to non-controlling interests	(206.5)						(206.5)
Ending balance at Sep. 30, 2024	4,274	0.6	711.3	(139.2)	6,738.1	(3,994.5)	957.7
Beginning balance at Jun. 30, 2024	4,262.7	0.6	712.8	(163.7)	6,614.7	(3,833.5)	931.8
Increase (Decrease) in Stockholders' Equity
Net income	185.8				123.6		62.2
Other comprehensive income (loss), net of tax	40.2			24.5			15.7
Share-based compensation	10.2		10.2
Common stock issued under share-based incentive plans	(58.2)		(0.8)			(57.4)
Share repurchases	(103.6)					(103.6)
Dividends	(0.2)				(0.2)
Affiliate equity activity:
Affiliate equity compensation	11.3		1.6				9.7
Purchases	(1.2)		(0.5)				(0.7)
Changes in redemption value of Redeemable non-controlling interests	(12)		(12)
Capital contributions and other	(2.1)						(2.1)
Distributions to non-controlling interests	(58.9)						(58.9)
Ending balance at Sep. 30, 2024	$ 4,274	$ 0.6	$ 711.3	$ (139.2)	$ 6,738.1	$ (3,994.5)	$ 957.7

CONSOLIDATED STATEMENTS OF CH_2

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Stockholders' Equity [Abstract]
Dividends (in dollars per share)	$ 0.01	$ 0.01	$ 0.03	$ 0.03

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flow from (used in) operating activities:
Net income	$ 519.5	$ 661.9
Adjustments to reconcile Net income to cash flow from (used in) operating activities:
Intangible amortization and impairments	21.8	37.5
Depreciation and other amortization	9.4	10
Deferred income tax expense	59.5	13
Equity method income (net)	(188.3)	(154.3)
Affiliate Transaction gain	0	(133.1)
Distributions received from equity method investments	357.3	421.7
Share-based compensation and Affiliate equity compensation expense	88.6	83.4
Net realized and unrealized gains on investment securities	(30.7)	(68.7)
Other non-cash items	(3.8)	(3.7)
Changes in assets and liabilities:
Purchases of securities by consolidated Affiliate sponsored investment products	(61.8)	(32.6)
Sales of securities by consolidated Affiliate sponsored investment products	48.1	38.9
Increase in receivables	(76.5)	(116.4)
Decrease in other assets	13.8	23.3
Decrease in payables, accrued liabilities, and other liabilities	(37.3)	(161.5)
Cash flow from operating activities	719.6	619.4
Cash flow from (used in) investing activities:
Investments in Affiliates, net of cash acquired	(5.9)	(93.8)
Proceeds from Affiliate Transaction	0	294
Purchase of fixed assets	(2.3)	(6.6)
Purchase of investment securities	(496.4)	(477.6)
Maturities and sales of investment securities	875.2	761.9
Cash flow from investing activities	370.6	477.9
Cash flow from (used in) financing activities:
Borrowings of senior bank debt, senior notes, and junior subordinated notes	847.6	25
Repayments of senior bank debt and senior notes	(750)	(25)
Repurchases of common stock (net)	(589.5)	(213.6)
Dividends paid on common stock	(1)	(1.2)
Distributions to non-controlling interests	(206.5)	(216.4)
Affiliate equity purchases (net)	(54.1)	(28.3)
Redemptions of consolidated Affiliate sponsored investment products (net)	(6.3)	(9.7)
Other financing items	(144.3)	(54.8)
Cash flow used in financing activities	(904.1)	(524)
Effect of foreign currency exchange rate changes on cash and cash equivalents	5.7	(0.2)
Net increase in cash and cash equivalents	191.8	573.1
Cash and cash equivalents at beginning of period	813.6	429.2
Effect of (deconsolidation) consolidation of Affiliates and Affiliate sponsored investment products	5.3	(3.1)
Cash and cash equivalents at end of period	$ 1,010.7	$ 999.2

Basis of Presentation and Use o

Basis of Presentation and Use of Estimates	9 Months Ended
Basis of Presentation and Use of Estimates	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The Consolidated Financial Statements of Affiliated Managers Group, Inc. (“AMG” or the “Company”) have been prepared in accordance with accounting principles generally accepted in the U.S. (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for full year financial statements. In the opinion of management, all normal and recurring adjustments considered necessary for a fair statement of the Company’s interim financial position and results of operations have been included and all intercompany balances and transactions have been eliminated. Operating results for interim periods are not necessarily indicative of the results that may be expected for any other period or for the full year. The Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2023 includes additional information about its operations, financial position, and accounting policies, and should be read in conjunction with this Quarterly Report on Form 10-Q. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts and disclosures in the financial statements. Actual results could differ from those estimates. All amounts in these notes, except per share data in the text and tables herein, are stated in millions unless otherwise indicate d .

Accounting Standards and Polici

Accounting Standards and Policies	9 Months Ended
Accounting Standards and Policies	Sep. 30, 2024
Accounting Policies [Abstract]
Accounting Standards and Policies	Accounting Standards and Policies Recently Adopted Accounting Standards Effective January 1, 2024, the Company adopted Accounting Standard Update (“ASU”) 2022-03, Fair Value Measurement (Topic 820): Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions. The adoption of this standard did not have a material impact on the Company’s Consolidated Financial Statements. Recent Accounting Developments In November 2023, the Financial Accounting Standards Board (“FASB”) issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires disclosure of incremental segment information on an annual and interim basis for all public entities to enable investors to develop more decision-useful financial analyses. The standard is effective for annual periods beginning after December 15, 2023 and for interim periods beginning after December 15, 2024. The Company currently does not expect the adoption to have a material impact on its Consolidated Financial Statements. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which requires greater disaggregation of income tax disclosures related to the income tax rate reconciliation and income taxes paid. The standard is effective for annual periods beginning after December 15, 2024. The Company currently does not expect the adoption to have a material impact on its Consolidated Financial Statements. In March 2024, the FASB issued ASU 2024-01, Compensation—Stock Compensation (Topic 718): Scope Application of Profits Interest and Similar Awards, which clarifies how an entity should apply the scope guidance to determine whether profits interest and similar awards should be accounted for in accordance with Topic 718. The standard is effective for interim and annual periods beginning after December 15, 2024 for the Company, and is effective for interim and annual periods beginning after December 15, 2025 for the Company’s Affiliates. The Company currently does not expect the adoption to have a material impact on its Consolidated Financial Statements.

Investments in Marketable Secur

Investments in Marketable Securities	9 Months Ended
Investments in Marketable Securities	Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Investments in Marketable Securities	Investments in Marketable Securities Equity Securities The following table summarizes the cost, gross unrealized gains, gross unrealized losses, and fair value of investments in equity securities: December 31, 2023 September 30, 2024 Cost $ 35.3 $ 37.6 Unrealized gains 2.6 4.7 Unrealized losses (0.0) (0.3) Fair value $ 37.9 $ 42.0 As of December 31, 2023 and September 30, 2024 , investments in equity securities include consolidated Affiliate sponsored investment products with fair values of $15.8 million and $11.9 million , respectively. For the three months ended September 30, 2023 , the Company recognized net unrealized losses on equity securities still held as of September 30, 2023 of $2.1 million . For the nine months ended September 30, 2023, the Company recognized net unrealized gains on equity securities still held as of September 30, 2023 of $1.3 million . For the three and nine months ended September 30, 2024 , the Company recognized net unrealized gains on equity securities still held as of September 30, 2024 of $2.0 million and $3.5 million , respectively. Debt Securities The following table summarizes the cost, gross unrealized gains, gross unrealized losses, and fair value of investments in U.S. Treasury securities classified as available-for-sale, all of which matured during the nine months ended September 30, 2024 , and consolidated Affiliate sponsored investment products classified as trading: Available-for-Sale Trading December 31, 2023 September 30, 2024 December 31, 2023 September 30, 2024 Cost $ 405.4 $ — $ 17.9 $ 23.3 Unrealized gains 0.0 — — 0.8 Unrealized losses (0.1) — (0.1) — Fair value $ 405.3 $ — $ 17.8 $ 24.1 For the three and nine months ended September 30, 2023 , the Company received $178.4 million and $280.1 million of proceeds from the maturity of available-for sale securities, respectively, and purchased $245.3 million and $420.3 million of available-for-sale securities, respectively. For the three months ended September 30, 2024 , the Company received $100.0 million of proceeds from the maturity of available-for-sale securities and purchased no available-for-sale securities. For the nine months ended September 30, 2024 , the Company received $825.2 million of proceeds from the maturity of available-for- sale securities and purchased $413.9 million of available-for-sale securities. For the three and nine months ended September 30, 2023 , the Company recognized net unrealized gains on debt securities classified as trading still held as of September 30, 2023 of $0.0 million and $0.0 million , respectively. For the three and nine months ended September 30, 2024 , the Company recognized net unrealized gains on debt securities classified as trading still held as of September 30, 2024 of $0.8 million and $1.4 million , respectively.

Other Investments

Other Investments	9 Months Ended
Other Investments	Sep. 30, 2024
Investments, All Other Investments [Abstract]
Other Investments	Other Investments Other investments consists primarily of investments in funds advised by the Company’s Affiliates that are carried at net asset value (“NAV”) as a practical expedient and other investments without readily determinable fair values. Any gain or loss related to these investments is recorded in Investment and other income in the Consolidated Statements of Income. Investments Measured at NAV as a Practical Expedient The Company’s Affiliates sponsor funds in which the Company and its Affiliates may make general partner and seed capital investments. These funds generally operate in partnership form and apply the specialized fair value accounting for investment companies. The Company accounts for its interests in these funds using the equity method of accounting and is required to retain the specialized fair value accounting of the investment companies. Because the funds’ investments do not have readily determinable fair values, the Company uses the NAV of these investments as a practical expedient for their fair values. The following table summarizes the fair values of these investments and any related unfunded commitments: December 31, 2023 September 30, 2024 Fair Value Unfunded Commitments Fair Value Unfunded Commitments Private equity funds (1) $ 424.4 $ 187.2 $ 477.5 $ 215.7 Investments in other strategies (2) 6.1 — 4.9 — Total (3) $ 430.5 $ 187.2 $ 482.4 $ 215.7 ___________________________ (1) The Company accounts for the majority of its interests in private equity funds one quarter in arrears (adjusted for current period calls and distributions). These funds primarily invest in a broad range of third-party funds and direct investments. Distributions will be received as the underlying assets are liquidated over the life of the funds, which is generally up to 15 years . (2) These are multi-disciplinary funds that invest across various asset classes and strategies, including equity and credit. Investments are generally redeemable on a daily, monthly, or quarterly basis. (3) Fair value attributable to the controlling interest was $324.9 million and $363.4 million as of December 31, 2023 and September 30, 2024 , respectively. Investments Without Readily Determinable Fair Values The Company made an investment in a private corporation where it does not exercise significant influence. Because this investment does not have a readily determinable fair value, the Company has elected to measure this investment at its cost minus impairments, if any, plus or minus changes resulting from observable price changes in orderly transactions for identical or similar investments in the private corporation. The following table summarizes the cost, cumulative unrealized gains, and carrying amount of investments without readily determinable fair values: December 31, 2023 September 30, 2024 Cost $ 8.5 $ 8.5 Cumulative unrealized gains 41.9 41.9 Carrying amount $ 50.4 $ 50.4 For the three and nine months ended September 30, 2024 , the Company recorded no gains or losses on the underlying investment. The following table presents the changes in Other investments: For the Three Months Ended September 30, 2023 2024 Measured at NAV as a Practical Expedient Without Readily Determinable Fair Values Total Measured at NAV as a Practical Expedient Without Readily Determinable Fair Values Total Balance, beginning of period $ 406.6 $ 50.4 $ 457.0 $ 479.9 $ 50.4 $ 530.3 Purchases and commitments 16.0 — 16.0 13.6 — 13.6 Sales and distributions (20.5) — (20.5) (20.4) — (20.4) Net realized and unrealized gains 5.4 — 5.4 9.3 — 9.3 Balance, end of period $ 407.5 $ 50.4 $ 457.9 $ 482.4 $ 50.4 $ 532.8 For the Nine Months Ended September 30, 2023 2024 Measured at NAV as a Practical Expedient Without Readily Determinable Fair Values Total Measured at NAV as a Practical Expedient Without Readily Determinable Fair Values Total Balance, beginning of period $ 371.2 $ 50.4 $ 421.6 $ 430.5 $ 50.4 $ 480.9 Purchases and commitments 62.0 — 62.0 78.1 — 78.1 Sales and distributions (49.4) — (49.4) (47.1) — (47.1) Net realized and unrealized gains 23.7 — 23.7 20.9 — 20.9 Balance, end of period $ 407.5 $ 50.4 $ 457.9 $ 482.4 $ 50.4 $ 532.8

Fair Value Measurements

Fair Value Measurements	9 Months Ended
Fair Value Measurements	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurement s The following tables summarize financial assets and liabilities that are measured at fair value on a recurring basis: Fair Value Measurements December 31, 2023 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets Investments in equity securities (1) $ 37.9 $ 37.9 $ — $ — Investments in debt securities (1) 423.1 — 423.1 — Financial Liabilities (2) Contingent payment obligations $ 14.7 $ — $ — $ 14.7 Affiliate equity purchase obligations 53.9 — — 53.9 Fair Value Measurements September 30, 2024 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets Investments in equity securities (1) $ 42.0 $ 42.0 $ — $ — Investments in debt securities (1) 24.1 — 24.1 — Financial Liabilities (2) Contingent payment obligations $ 6.5 $ — $ — $ 6.5 Affiliate equity purchase obligations 58.9 — — 58.9 ___________________________ (1) Amounts are recorded in Investments in marketable securities on the Consolidated Balance Sheets. (2) Amounts are recorded in Other liabilities on the Consolidated Balance Sheets. Level 3 Financial Liabilities The following table presents the changes in Level 3 liabilities: For the Three Months Ended September 30, 2023 2024 Contingent Payment Obligations Affiliate Equity Purchase Obligations Contingent Payment Obligations Affiliate Equity Purchase Obligations Balance, beginning of period $ 23.4 $ 68.4 $ 7.9 $ 53.9 Purchases and issuances (1) — 4.7 — 10.1 Settlements and reductions — (25.4) — (5.0) Net realized and unrealized gains (2) (5.2) (2.5) (1.4) (0.1) Balance, end of period $ 18.2 $ 45.2 $ 6.5 $ 58.9 Net change in unrealized (gains) losses relating to instruments still held at the reporting date (1) $ (5.2) $ (2.4) $ (1.4) $ (0.5) For the Nine Months Ended September 30, 2023 2024 Contingent Payment Obligations Affiliate Equity Purchase Obligations Contingent Payment Obligations Affiliate Equity Purchase Obligations Balance, beginning of period $ 21.0 $ 24.5 $ 14.7 $ 53.9 Purchases and issuances (1) — 75.7 — 66.3 Settlements and reductions — (49.7) — (62.1) Net realized and unrealized (gains) losses (2) (2.8) (5.3) (8.2) 0.8 Balance, end of period $ 18.2 $ 45.2 $ 6.5 $ 58.9 Net change in unrealized (gains) losses relating to instruments still held at the reporting date (1) $ (2.8) $ (4.5) $ (8.2) $ 0.4 ___________________________ (1) Affiliate equity purchase obligation activity includes transfers from Redeemable non-controlling interests. (2) Gains and losses resulting from changes to expected payments are included in Other expenses (net) in the Consolidated Statements of Income and the accretion of these obligations is included in Interest expense in the Consolidated Statements of Income. The following table presents certain quantitative information about the significant unobservable inputs used in valuing the Company’s Level 3 fair value measurements: Quantitative Information About Level 3 Fair Value Measurements December 31, 2023 September 30, 2024 Valuation Techniques Unobservable Input Fair Value Range Weighted Average (1) Fair Value Range Weighted Average (1) Contingent payment obligations Monte Carlo Simulation Volatility $ 14.7 19% - 25% 21 % $ 6.5 10% - 18% 11 % Discount rates 6% 6 % 5% 5 % Affiliate equity purchase obligations Discounted cash flow Growth rates (2) $ 53.9 (6)% - 7% 1 % $ 58.9 (5)% - 8% 0 % Discount rates 14% - 17% 14 % 14% - 18% 15 % ___________________________ (1) Calculated by comparing the relative fair value of an obligation to its respective total. (2) Represents growth rates of asset- and performance-based fees. Contingent payment obligations represent the fair value of the expected future settlement amounts related to the Company’s investments in its consolidated Affiliates. Changes to assumed volatility and discount rates change the fair value of contingent payment obligations. Increases to the volatility rates used would result in higher fair values, while increases to the discount rates used would result in lower fair values. Affiliate equity purchase obligations include agreements to purchase Affiliate equity and represent the fair value of the expected future settlement amounts. Changes to assumed growth rates and discount rates change the fair value of the Affiliate equity purchase obligations. Increases to the assumed growth rates would result in higher fair values, while increases to the discount rates used would result in lower fair values. Other Financial Assets and Liabilities Not Carried at Fair Value The following table summarizes the Company’s other financial liabilities not carried at fair value: December 31, 2023 September 30, 2024 Carrying Value Fair Value Carrying Value Fair Value Fair Value Hierarchy Senior notes $ 1,099.4 $ 1,049.8 $ 1,097.3 $ 1,075.8 Level 2 Junior subordinated notes 765.9 612.0 1,216.0 1,129.6 Level 2 Junior convertible securities 341.7 340.9 341.7 375.9 Level 2 The Company has other financial assets and liabilities that are not required to be carried at fair value, but are required to be disclosed at fair value. The carrying amount of Cash and cash equivalents, Receivables, Payables and accrued liabilities, and certain Other liabilities approximates fair value because of the short-term nature of these instruments. The carrying value of the credit facilities (as defined in Note 7) approximates fair value because the credit facilities have variable interest based on selected short-term rates.

Investments in Affiliates and A

Investments in Affiliates and Affiliate Sponsored Investment Products	9 Months Ended
	Sep. 30, 2024
Variable Interest Entities [Abstract]
Investments in Affiliates and Affiliate Sponsored Investment Products	Investments in Affiliates and Affiliate Sponsored Investment Products In evaluating whether an investment must be consolidated, the Company evaluates the risk, rewards, and significant terms of each of its Affiliates and other investments to determine if an investment is considered a voting rights entity (“VRE”) or a variable interest entity (“VIE”). An entity is a VRE when the total equity investment at risk is sufficient to enable the entity to finance its activities independently, and when the equity holders have the obligation to absorb losses, the right to receive residual returns, and the right to direct the activities of the entity that most significantly impact its economic performance. An entity is a VIE when it lacks one or more of the characteristics of a VRE, which, for the Company, are Affiliate investments structured as partnerships (or similar entities) where the Company is a limited partner and lacks substantive kick-out or substantive participation rights over the general partner. Assessing whether an entity is a VRE or VIE involves judgment. Upon the occurrence of certain events, management reviews and reconsiders its previous conclusion regarding the status of an entity as a VRE or a VIE. The Company consolidates VREs when it has control over significant operating, financial, and investing decisions of the entity. When the Company lacks such control, but is deemed to have significant influence, the Company accounts for the VRE under the equity method. Investments with readily determinable fair values in which the Company does not have rights to exercise significant influence are recorded at fair value on the Consolidated Balance Sheets, with changes in fair value included in Investment and other income. The Company consolidates VIEs when it is the primary beneficiary of the entity, which is defined as having the power to direct the activities that most significantly impact the VIE’s economic performance and the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to the VIE. Substantially all of the Company’s consolidated Affiliates considered VIEs are controlled because the Company holds a majority of the voting interests or it is the managing member or general partner. Furthermore, an Affiliate’s assets can be used for purposes other than the settlement of the respective Affiliate’s obligations. The Company applies the equity method of accounting to VIEs where the Company is not the primary beneficiary, but has the ability to exercise significant influence over operating and financial matters of the VIE. Investments in Affiliates Substantially all of the Company’s Affiliates are considered VIEs and are either consolidated or accounted for under the equity method. A limited number of the Company’s Affiliates are considered VREs and most of these are accounted for under the equity method. When an Affiliate is consolidated, the portion of the earnings attributable to Affiliate management’s and any co-investor’s equity ownership is included in Net income (non-controlling interests) in the Consolidated Statements of Income. Undistributed earnings attributable to Affiliate management’s and any co-investor’s equity ownership, along with their share of any tangible or intangible net assets, are included in Non-controlling interests on the Consolidated Balance Sheets. Affiliate equity interests where the holder has certain rights to demand settlement are presented, at their current redemption values, as Redeemable non-controlling interests or Other liabilities on the Consolidated Balance Sheets. The Company periodically issues, sells, and purchases the equity of its consolidated Affiliates. Because these transactions take place between entities that are under common control, any gains or losses attributable to these transactions are required to be included in Additional paid- in capital in the Consolidated Balance Sheets, net of any related income tax effects in the period the transaction occurs. When an Affiliate is accounted for under the equity method, the Company’s share of an Affiliate’s earnings or losses, net of amortization and impairments, is included in Equity method income (net) in the Consolidated Statements of Income and the carrying value of the Affiliate is recorded in Equity method investments in Affiliates (net) in the Consolidated Balance Sheets. The Company periodically performs assessments to determine if the fair value of an investment may have declined below its related carrying value for its Affiliates accounted for under the equity method for a period that the Company considers to be other-than-temporary. The Company performs these assessments if certain triggering events occur or annually during the fourth quarter. The Company first considers whether certain qualitative factors indicate an increased likelihood of a decline in the fair value of an Affiliate during the reporting period. If such a decline is identified, and it is likely that an investment’s fair value may have declined below its carrying value, the Company performs a quantitative assessment to determine if an impairment exists. Impairments are recorded as an expense in Equity method income (net) to reduce the carrying value of the Affiliate to fair value. The unconsolidated assets, net of liabilities and non-controlling interests of Affiliates accounted for under the equity method considered VIEs, and the Company’s carrying value and maximum exposure to loss, were as follows: December 31, 2023 September 30, 2024 Unconsolidated VIE Net Assets Carrying Value and Maximum Exposure to Loss Unconsolidated VIE Net Assets Carrying Value and Maximum Exposure to Loss Affiliates accounted for under the equity method $ 1,492.4 $ 2,198.2 $ 1,173.6 $ 2,042.7 As of December 31, 2023 and September 30, 2024 , the carrying value and maximum exposure to loss for all of the Company’s Affiliates accounted for under the equity method was $2,288.5 million and $2,148.4 million , respectively, including Affiliates accounted for under the equity method considered VREs of $90.3 million and $105.7 million , respectively. Affiliate Sponsored Investment Products The Company’s Affiliates sponsor various investment products where the Affiliate also acts as the investment adviser. These investment products are typically owned primarily by third-party investors; however, certain products are funded with general partner and seed capital investments from the Company and its Affiliates. Third-party investors in Affiliate sponsored investment products are generally entitled to substantially all of the economics of these products, except for the asset- and performance-based fees earned by the Company’s Affiliates or any gains or losses attributable to the Company’s or its Affiliates’ investments in these products. As a result, the Company generally does not consolidate these products. However, for certain products, the Company’s consolidated Affiliates, as the investment manager, have the power to direct the activities of the investment product and have an exposure to the economics of the VIE that is more than insignificant, though generally only for a short period while the product is established and has yet to attract significant third-party investors. When the products are consolidated, the Company retains the specialized investment company accounting principles of the underlying products, and all of the underlying investments are carried at fair value in Investments in marketable securities, with corresponding changes in the investments’ fair values included in Investment and other income. Purchases and sales of securities are included in purchases and sales by consolidated Affiliate sponsored investment products in the Consolidated Statements of Cash Flows, respectively, and the third-party investors’ interests are recorded in Redeemable non-controlling interests. When the Company or its consolidated Affiliates no longer control these products, due to a reduction in ownership or other reasons, the products are deconsolidated with only the Company’s or its consolidated Affiliate’s investment in the product reported from the date of deconsolidation. The Company’s carrying value and maximum exposure to loss from unconsolidated Affiliate sponsored investment products, is its or its consolidated Affiliates’ interests in the unconsolidated net assets of the respective products. The net assets of unconsolidated VIEs attributable to Affiliate sponsored investment products, and the Company’s carrying value and maximum exposure to loss, were as follows: December 31, 2023 September 30, 2024 Unconsolidated VIE Net Assets Carrying Value and Maximum Exposure to Loss Unconsolidated VIE Net Assets Carrying Value and Maximum Exposure to Loss Affiliate sponsored investment products $ 5,788.3 $ 29.8 $ 5,332.2 $ 24.4

Debt

Debt	9 Months Ended
Debt	Sep. 30, 2024
Debt Disclosure [Abstract]
Debt	Debt The following table summarizes the Company’s Debt: December 31, 2023 September 30, 2024 Senior bank debt $ 349.9 $ — Senior notes 1,096.9 1,091.7 Junior subordinated notes 751.8 1,189.0 Junior convertible securities 338.9 339.0 Debt $ 2,537.5 $ 2,619.7 The Company’s senior bank debt, senior notes, junior subordinated notes, and junior convertible securities are carried at amortized cost. Unamortized discounts and debt issuance costs associated with the Company’s debt instruments, with the exception of its senior unsecured multicurrency revolving credit facility (the “revolver”), are presented on the Consolidated Balance Sheets as an adjustment to the carrying value of the associated debt. Senior Bank Debt During the nine months ended September 30, 2024 , the Company repaid the $350.0 million outstanding under its senior unsecured term loan facility (the “term loan” ). As of September 30, 2024 , the Company had a $1.25 billion revolver (together with the term loan, the “credit facilities”). The revolver matures on October 25, 2027 and the term loan terminated upon payment in full. Subject to certain conditions, the Company may increase the commitments under the revolver by up to an additional $500.0 million . The Company pays interest on any outstanding obligations under the revolver at a specified rate, currently based either on an applicable term-SOFR plus a SOFR adjustment of 0.10% , or prime rate, plus a marginal rate determined based on its credit rating. Through the repayment dates, the interest rate for the Company’s outstanding borrowings under the term loan was term-SOFR plus a SOFR adjustment of 0.10% , plus the marginal rate of 0.85% . As of December 31, 2023 and September 30, 2024 , the Company had no outstanding borrowings under the revolver. Senior Notes In the first quarter of 2024, the Company’s $400.0 million 4.25% senior notes matured and were fully repaid . As of September 30, 2024 , the Company had senior notes outstanding. The carrying values of the senior notes are accreted to their principal amount at maturity over the remaining life of the underlying instrument. The principal terms of the senior notes outstanding as of September 30, 2024 are presented and described below: 2025 Senior Notes 2030 Senior Notes 2034 Senior Notes Issue date February 2015 June 2020 August 2024 Maturity date August 2025 June 2030 August 2034 Par value (in millions) $ 350.0 $ 350.0 $ 400.0 Stated coupon 3.50 % 3.30 % 5.50 % Coupon frequency Semi-annually Semi-annually Semi-annually Call price As defined As defined As defined On August 20, 2024, the Company issue d $400.0 million aggregate principal amount of senior unsecured notes with a maturity date of August 20, 2034 (the “2034 senior notes”). Interest is payable beginning February 20, 2025. In addition to customary event of default provisions, the indenture governing the 2034 senior notes limits the Company's ability to consolidate, merge, or sell all or substantially all of its assets and requires the Company to make an offer to repurchase the 2034 senior notes upon certain change of control triggering events. The senior notes may be redeemed, in whole or in part, at a make-whole redemption price (plus accrued and unpaid interest), at any time, in the case of the 2025 senior notes, at any time prior to March 15, 2030, in the case of the 2030 senior notes, and at any time prior to May 20, 2034, in the case of the 2034 senior notes. The make-whole redemption price, in each case, is equal to the greater of 100% of the principal amount of the notes to be redeemed and the remaining principal and interest payments on the notes being redeemed (excluding accrued but unpaid interest to, but not including, the redemption date) discounted to their present value as of the redemption date at the applicable treasury rate plus 0.25% , in the case of the 2025 and 2034 senior notes, and to their present value as of the redemption date on a semi-annual basis at the applicable treasury rate plus 0.40% , in the case of the 2030 senior notes. In addition, the 2030 and 2034 senior notes may be redeemed, in whole or in part, at any time, on or after March 15, 2030 and May 20, 2034, respectively, at a redemption price equal to 100% of the principal amount of the notes to be redeemed plus accrued and unpaid interest thereon to, but not including, the redemption date. Junior Subordinated Notes As of September 30, 2024 , the Company had junior subordinated notes outstanding, the respective principal terms of which are presented and described below: 2059 Junior Subordinated Notes 2060 Junior Subordinated Notes 2061 Junior Subordinated Notes 2064 Junior Subordinated Notes Issue date March 2019 September 2020 July 2021 March 2024 Maturity date March 2059 September 2060 September 2061 March 2064 Par value (in millions) $ 300.0 $ 275.0 $ 200.0 $ 450.0 Stated coupon 5.875 % 4.75 % 4.20 % 6.75 % Coupon frequency Quarterly Quarterly Quarterly Quarterly Call price As defined As defined As defined As defined NYSE Symbol MGR MGRB MGRD MGRE On March 20, 2024, the Company issued $450.0 million of junior subordinated notes with a maturity date of March 30, 2064 (the “2064 junior subordinated notes”). Interest was payable beginning June 30, 2024. The 2064 junior subordinated notes were issued at 100% of the principal amount and rank junior and subordinate in right of payment and upon liquidation to all of the Company’s current and future senior indebtedness. As of September 30, 2024 , the 2059 junior subordinated notes could be redeemed at any time, in whole or in part. The other junior subordinated notes may be redeemed at any time, in whole or in part, on or after September 30, 2025, in the case of the 2060 junior subordinated notes, on or after September 30, 2026, in the case of the 2061 junior subordinated notes, and on or after March 30, 2029, in the case of the 2064 junior subordinated notes. In each case, the junior subordinated notes may be redeemed at 100% of the principal amount of the notes being redeemed, plus any accrued and unpaid interest thereon. Prior to the applicable redemption date, at the Company’s option, the applicable junior subordinated notes may also be redeemed, in whole but not in part, at 100% of the principal amount, plus any accrued and unpaid interest, if certain changes in tax laws, regulations, or interpretations occur; or at 102% of the principal amount, plus any accrued and unpaid interest, if a rating agency makes certain changes relating to the equity credit criteria for securities with features similar to the applicable notes. The Company may, at its option, and subject to certain conditions and restrictions, defer interest payments subject to the terms of the junior subordinated notes. Junior Convertible Securities As of September 30, 2024 , the Company had $341.7 million of principal outstanding in its 5.15% junior convertible trust preferred securities (the “junior convertible securities”), maturing in 2037. The junior convertible securities bear interest at a rate of 5.15% per annum, payable quarterly in cash. As of December 31, 2023 and September 30, 2024 , the unamortized issuance costs related to the junior convertible securities were $2.9 million and $2.7 million , respectively. The following table presents interest expense recorded in connection with the junior convertible securities: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Contractual interest expense $ 4.4 $ 4.4 $ 13.2 $ 13.2 Amortization of debt issuance costs 0.1 0.1 0.2 0.2 Total $ 4.5 $ 4.5 $ 13.4 $ 13.4 Effective interest rate 5.21 % 5.21 % 5.21 % 5.21 % Holders of the junior convertible securities have no rights to put these securities to the Company. The holder may convert the securities to 0.2558 shares of common stock per $50.00 junior convertible security, equivalent to an adjusted conversion price of $195.47 per share. The conversion rate is subject to adjustments as described in the Amended and Restated Declaration of Trust of AMG Capital Trust II and the related indenture, both dated October 17, 2007 and filed as exhibits to the Company’s most recent Annual Report on Form 10-K. Upon conversion, holders will receive cash or shares of the Company’s common stock, or a combination thereof, at the Company’s election. The Company may redeem the junior convertible securities if the closing price of its common stock for 20 trading days in a period of 30 consecutive trading days exceeds 130% of the then prevailing conversion price, and may also repurchase junior convertible securities in the open market or in privately negotiated transactions from time to time at management’s discretion. The Company did not repurchase any of its junior convertible securities during the nine months ended September 30, 2023 and 2024 .

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies From time to time, the Company and its Affiliates may be subject to claims, legal proceedings, and other contingencies in the ordinary course of their business activities. Any such matters are subject to various uncertainties, and it is possible that some of these matters may be resolved in a manner unfavorable to the Company or its Affiliates. The Company and its Affiliates establish accruals, as necessary, for matters for which the outcome is probable and the amount of the liability can be reasonably estimated. The Company has committed to co-invest in certain Affiliate sponsored investment products. As of September 30, 2024 , these unfunded commitments were $215.7 million an d may be called in future periods. As of September 30, 2024 , the Company was obligated to make deferred payments and was contingently liable to make payments in connection with certain of its consolidated Affiliates, which are included in Other liabilities, as follows: Earliest Payable Controlling Interest Co-Investor Total 2024 2025 Deferred payment obligations $ 43.3 $ — $ 43.3 $ 21.7 $ 21.6 Contingent payment obligations (1) 6.4 0.1 6.5 — 6.5 ___________________________ (1) Fair value as of September 30, 2024 . The Company is contingently liable to make maximum contingent payments of up to $110.0 million ( $24.9 million attributable to the co-investor), all of which may become payable in 2025. As of September 30, 2024 , the Company was obligated to make deferred payments of $5.1 million related to certain of its investments in Affiliates accounted for under the equity method, all of which is payable during the remainder of 2024 . Deferred payment obligations are included in Other liabilities. As of September 30, 2024 , the Company was contingently liable to make payments of $243.1 million related to the achievement of specified financial targets by certain of its Affiliates accounted for under the equity method, of which $4.0 million may become payable during the remainder of 2024 and $239.1 million may become payable from 2025 through 2028. As of September 30, 2024 , the Company has agreed to provide one of its Affiliates accounted for under the equity method up to $50.0 million of contingent financing. In the event that certain financial targets are not met, the Company may receive payments from one of its Affiliates accounted for under the equity method of up to $12.5 million and also has the option to reduce its ownership interest and receive an incremental payment of $25.0 million . Affiliate equity interests provide holders at consolidated Affiliates with a conditional right to put their interests to the Company over time. See Note 14. The Company and certain of its consolidated Affiliates operate under regulatory authorities that require the maintenance of minimum financial or capital requirements. The Company’s management is not aware of any significant violations of such requirements.

Goodwill and Acquired Client Re

Goodwill and Acquired Client Relationships	9 Months Ended
Goodwill and Acquired Client Relationships	Sep. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Acquired Client Relationships	G oodwill and Acquired Client Relationshi p s The following table presents the changes in the Company’s consolidated Goodwill: Goodwill Balance, as of December 31, 2023 $ 2,523.6 Foreign currency translation 8.4 Balance, as of September 30, 2024 $ 2,532.0 As of September 30, 2024 the Company completed its annual impairment assessment on goodwill and no impairment was indicated. The following table presents the changes in the Company’s components of Acquired client relationships (net): Acquired Client Relationships (Net) Definite-lived Indefinite-lived Total Gross Book Value Accumulated Amortization Net Book Value Net Book Value Net Book Value Balance, as of December 31, 2023 $ 1,260.5 $ (1,051.2) $ 209.3 $ 1,603.1 $ 1,812.4 Intangible amortization and impairments — (21.8) (21.8) — (21.8) Foreign currency translation 4.0 (4.0) — 16.5 16.5 Balance, as of September 30, 2024 $ 1,264.5 $ (1,077.0) $ 187.5 $ 1,619.6 $ 1,807.1 Definite-lived acquired client relationships at the Company’s consolidated Affiliates are amortized over their expected period of economic benefit. The Company recorded amortization expense in Intangible amortization and impairments in the Consolidated Statements of Income for these relationships of $12.5 million and $37.5 million for the three and nine months ended September 30, 2023 , respectively, and $7.3 million and $21.8 million for the three and nine months ended September 30, 2024 , respectively. Based on relationships existing as of September 30, 2024 , the Company estimates that its consolidated amortization expense will be approximately $7 million for the remainder of 2024, approximately $25 million in each of 2025, 2026, 2027, and 2028, and approximately $15 million in 2029. Veritable Transaction In the third quarter of 2023, the Company completed the sale of its equity interest in Veritable, LP (“Veritable”), one of the Company’s consolidated Affiliates. Pursuant to the terms of the agreement, under which a third party acquired 100% of the outstanding equity interests in Veritable, the Company received $287.4 million in cash, net of transaction costs. Veritable was included in the Company’s results through the closing date, and the Company’s gain on the transaction was $133.1 million , which was recorded in Affiliate Transaction gain in the Consolidated Statements of Income.

Equity Method Investments in Af

Equity Method Investments in Affiliates	9 Months Ended
Equity Method Investments in Affiliates	Sep. 30, 2024
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments in Affiliates	Equity Method Investments in Affiliates In the second quarter of 2024 , the Company completed its minority investment in Suma Capital (“Suma”), a pan- European private markets firm that invests in the transition to a lower carbon economy. Following the close of the transaction, Suma partners continue to hold a significant majority of the equity of the firm and direct its day-to-day operations. The financial results of certain Affiliates accounted for under the equity method are recognized in the Consolidated Financial Statements one quarter in arrears. Equity method investments in Affiliates (net) consisted of the following: December 31, 2023 September 30, 2024 Goodwill $ 1,323.3 $ 1,348.1 Definite-lived acquired client relationships (net) 652.5 568.1 Indefinite-lived acquired client relationships (net) 122.6 122.4 Undistributed earnings and tangible capital 190.1 109.8 Equity method investments in Affiliates (net) $ 2,288.5 $ 2,148.4 The following table presents the changes in Equity method investments in Affiliates (net): Equity Method Investments in Affiliates (Net) Balance, as of December 31, 2023 $ 2,288.5 Investments in Affiliates 12.3 Earnings 292.6 Intangible amortization and impairments (104.3) Distributions of earnings (357.3) Foreign currency translation 16.6 Balance, as of September 30, 2024 $ 2,148.4 Definite-lived acquired client relationships at the Company’s Affiliates accounted for under the equity method are amortized over their expected period of economic benefit. The Company recorded amortization expense for these relationships of $21.2 million and $63.0 million for the three and nine months ended September 30, 2023 , respectively, and $22.7 million and $64.4 million for the three and nine months ended September 30, 2024 , respectively. Based on relationships existing as of September 30, 2024 , the Company estimates the amortization expense attributable to its Affiliates will be approximately $23 million for the remainder of 2024, approximately $75 million in 2025, approximately $70 million in each of 2026 and 2027, approximately $60 million in 2028, and approximately $45 million in 2029. In the second quarter of 2024, the Company recorded a $39.9 million expense to reduce the carrying value of an Affiliate to fair value. The decline in the fair value was a result of an anticipated decline in assets under management, which decreased the forecasted income associated with the investment. The fair value of the investment was determined using a discounted cash flow analysis, a Level 3 fair value measurement that included a projected compounded growth in assets under management over the next ten years of (2.5)% , long-term growth rate of 3% , discount rates of 12% and 20% for asset- and performance-based fees, respectively, and a market participant tax rate of 21% . Based on the discounted cash flow analysis, the Company concluded that the fair value of its investment had declined below its carrying value and that the decline was other-than- temporary. The Company had 22 Affiliates accounted for under the equity method as of December 31, 2023 and September 30, 2024 . The majority of these Affiliates are partnerships with structured interests that define how the Company will participate in Affiliate earnings, typically based upon a fixed percentage of revenue reduced by, in some cases, certain agreed-upon expenses. The partnership agreements do not define a fixed percentage for the Company’s ownership of the equity of the Affiliate. These percentages would be subject to a separate future negotiation if an Affiliate were to be sold or liquidated .

Related Party Transactions

Related Party Transactions	9 Months Ended
Related Party Transactions	Sep. 30, 2024
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions A p rior owner of one of the Company’s consolidated Affiliates retains interests in certain of the Affiliate’s private equity partnerships and, as a result, is a related party of the Company. The prior owner’s interests are included in Other liabilities and were $18.5 million and $15.0 million as of December 31, 2023 and September 30, 2024 , respectively. The Company may invest from time to time in funds or products advised by its Affiliates. The Company’s executive officers and directors may invest from time to time in funds advised or products offered by its Affiliates, or receive other investment services provided by its Affiliates, on substantially the same terms as other participating investors. In addition, the Company and its Affiliates earn asset- and performance-based fees and incur distribution and other expenses for services provided to Affiliate sponsored investment products. Affiliate management owners and the Company’s officers may serve as trustees or directors of certain investment vehicles from which the Company or an Affiliate earns fees. Also, from time to time, the Company may enter into ordinary course engagements for capital markets, banking, brokerage, and other services with beneficial owners of 5% or more of the Company’s voting securities. The Company has related party transactions in association with its deferred and contingent payment obligations, and Affiliate equity transactions, as more fully described in Notes 8, 13, and 14

Share-Based Compensation

Share-Based Compensation	9 Months Ended
Share-Based Compensation	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Share-Based Compensation	Share-Based Compensation The following table presents share-based compensation expense: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Share-based compensation expense $ 14.5 $ 10.2 $ 43.9 $ 42.1 Tax benefit 1.9 1.2 5.5 5.2 As of December 31, 2023 , the Company had unrecognized share-based compensation expense of $54.4 million . As of September 30, 2024 , the Company had unrecognized share-based compensation expense of $48.7 million , which will be recognized over a weighted average period of approximately two years (assuming no forfeitures). Restricted Stock The following table summarizes transactions in the Company’s restricted stock units: Restricted Stock Units Weighted Average Grant Date Value Unvested units—December 31, 2023 0.9 $ 138.51 Units granted 0.2 159.32 Units vested (0.3) 129.72 Units forfeited (0.0) 149.00 Performance condition changes 0.0 154.72 Unvested units—September 30, 2024 0.8 147.40 For the nine months ended September 30, 2023 and 2024 , the Company granted restricted stock units with fair values of $49.2 million and $31.3 million , respectively. These restricted stock units were valued based on the closing price of the Company’s common stock on the grant date and the number of shares expected to vest. Restricted stock units containing vesting conditions generally require service over a period of three years to four years and may also require the satisfaction of certain performance conditions. For awards with performance conditions, the number of restricted stock units expected to vest may change over time depending upon the performance level achieved. Stock Options The following table summarizes transactions in the Company’s stock options: Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Life (Years) Unexercised options outstanding—December 31, 2023 3.2 $ 76.74 Options granted — — Options exercised (1.3) 74.82 Options forfeited (0.0) 185.98 Options expired (0.0) 152.36 Performance condition changes 0.0 129.17 Unexercised options outstanding—September 30, 2024 1.9 78.02 2.1 Exercisable at September 30, 2024 1.5 75.89 1.9 The Company did not grant any stock options during the nine months ended September 30, 2023 and 2024 . Stock options generally vest over a period of three years to five years and expire seven years after the grant date. All stock options have been granted with exercise prices equal to the closing price of the Company’s common stock on the grant date. Substantially all of the Company’s outstanding stock options contain both service and performance conditions. For awards with performance

Redeemable Non-Controlling Inte

Redeemable Non-Controlling Interests	9 Months Ended
Redeemable Non-Controlling Interests	Sep. 30, 2024
Noncontrolling Interest [Abstract]
Redeemable Non-Controlling Interests	Redeemable Non-Controlling Interests Affiliate equity interests provide holders with an equity interest in one of the Company’s Affiliates, consistent with the structured partnership interests in place at the respective Affiliate. Affiliate equity holders generally have a conditional right to put their interests to the Company at certain intervals (between five years and 15 years from the date the equity interest is received by the Affiliate equity holder or on an annual basis following an Affiliate equity holder’s departure). Prior to becoming redeemable, the Company’s Affiliate equity is included in Non-controlling interests. Upon becoming redeemable, these interests are reclassified to Redeemable non-controlling interests at their current redemption values. Changes in the current redemption value are recorded to Additional paid-in capital. When the Company has an unconditional obligation to purchase Affiliate equity interests, the interests are reclassified from Redeemable non-controlling interests to Other liabilities at current fair value. Changes in fair value are recorded to Other expenses (net). The following table presents the changes in Redeemable non-controlling interests: Redeemable Non-controlling Interests Balance, as of December 31, 2023 (1) $ 393.4 Increase attributable to consolidated Affiliate sponsored investment products 1.5 Transfers to Other liabilities (42.2) Transfers from Non-controlling interests 1.7 Changes in redemption value 42.7 Balance, as of September 30, 2024 (1) $ 397.1 ___________________________ (1) As of December 31, 2023 and September 30, 2024 , Redeemable non-controlling interests include consolidated Affiliate sponsored investment products primarily attributable to third-party investors of $11.8 million and $13.3 million , respectively.

Affiliate Equity

Affiliate Equity	9 Months Ended
Affiliate Equity	Sep. 30, 2024
Affiliate Equity [Abstract]
Affiliate Equity	Affiliate Equity Affiliate equity interests are allocated income in a manner that is consistent with the structured partnership interests in place at the respective Affiliate. The Company’s Affiliates generally pay quarterly distributions to Affiliate equity holders. Distributions paid to non-controlling interest Affiliate equity holders were $216.4 million and $206.5 million fo r the nine months ended September 30, 2023 and 2024 , respectively. The Company periodically purchases Affiliate equity from and issues Affiliate equity to the Company’s consolidated Affiliate partners and other parties under agreements that provide the Company a conditional right to call and Affiliate equity holders the conditional right to put their Affiliate equity interests to the Company at certain intervals. The Company has the right to settle a portion of these purchases in shares of its common stock. For Affiliates accounted for under the equity method, the Company does not typically have such put and call arrangements. For the nine months ended September 30, 2023 and 2024 , the amount of cash paid for purchases was $41.7 million and $60.4 million , respectively. For the nine months ended September 30, 2023 and 2024 , the total amount of cash received for issuances was $13.4 million and $6.3 million , respectively. Sales and purchases of Affiliate equity generally occur at fair value; however, the Company also grants Affiliate equity to its consolidated Affiliate partners and other parties as a form of compensation. If the equity is issued for consideration below the fair value of the equity, or purchased for consideration above the fair value of the equity, the difference is recorded as compensation expense in Compensation and related expenses in the Consolidated Statements of Income over the requisite service period. The following table presents Affiliate equity compensation expense: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Controlling interest $ 0.0 $ 2.4 $ 6.1 $ 15.6 Non-controlling interests 11.5 9.7 33.4 30.9 Total $ 11.5 $ 12.1 $ 39.5 $ 46.5 The following table presents unrecognized Affiliate equity compensation expense: Controlling Interest Remaining Life Non-controlling Interests Remaining Life December 31, 2023 $ 30.6 5 years $ 235.7 6 years September 30, 2024 39.0 4 years 217.6 6 years The Company records amounts receivable from, and payable to, Affiliate equity holders in connection with the transfer of Affiliate equity interests that have not settled at the end of the period. The total receivable was $5.9 million and $4.5 million as of December 31, 2023 and September 30, 2024 , respectively, and was included in Other assets on the Consolidated Balance Sheets. The total payable was $53.9 million and $58.9 million a s of December 31, 2023 and September 30, 2024 , respectively, and was included in Other liabilities. Effects of Changes in the Company’s Ownership in Affiliates The Company periodically acquires interests from, and transfers interests to, Affiliate equity holders. Because these transactions do not result in a change of control, any gain or loss related to these transactions is recorded to Additional paid-in capital, which increases or decreases the controlling interest’s equity. No gain or loss related to these transactions is recorded in the Consolidated Statements of Income or the Consolidated Statements of Comprehensive Income. While the Company presents the current redemption value of Affiliate equity within Redeemable non-controlling interests, with changes in the current redemption value increasing or decreasing the controlling interest’s equity over time, the following table presents the cumulative effect that ownership changes had on the controlling interest’s equity related only to Affiliate equity transactions that occurred during the applicable periods: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Net income (controlling interest) $ 217.0 $ 123.6 $ 476.8 $ 349.5 Decrease in controlling interest paid-in capital from Affiliate equity issuances (4.5) — (13.1) (2.6) Increase (decrease) in controlling interest paid-in capital from Affiliate equity purchases 1.9 (0.5) (36.1) (22.9) Net income (controlling interest) including the net impact of Affiliate equity transactions $ 214.4 $ 123.1 $ 427.6 $ 324.0

Income Taxes

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company’s consolidated income tax provision includes taxes attributable to the controlling interest and, to a lesser extent, taxes attributable to the non-controlling interests. The following table presents the consolidated provision for income taxes: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Controlling interest (1) $ 75.9 $ 29.5 $ 149.9 $ 123.7 Non-controlling interests 1.8 1.8 5.5 6.3 Income tax expense $ 77.7 $ 31.3 $ 155.4 $ 130.0 Income before income taxes (controlling interest) $ 292.9 $ 153.1 $ 626.7 $ 473.2 Effective tax rate (controlling interest) (2) 25.9 % 19.3 % 23.9 % 26.1 % ___________________________ (1) For the three months ended September 30, 2023 and 2024 , income tax expense (controlling interest) included intangible- related deferred tax (benefit) expense of $(13.5) million and $16.4 million , respectively. For the nine months ended September 30, 2023 and 2024 , income tax expense (controlling interest) included intangible-related deferred tax expense of $16.4 million and $50.6 million , respectively. (2) Taxes attributable to the controlling interest divided by income before income taxes (controlling interest ) . The Company’s effective tax rate (controlling interest) for the three months ended September 30, 2023 was higher than the marginal tax rate of 24.5%, primarily due to the increase in the UK corporate tax rate in 2023. The Company’s effective tax rate (controlling interest) for the nine months ended September 30, 2023 was lower than the marginal tax rate primarily due to discrete foreign tax benefits and tax windfalls attributable to share-based compensation. The Company’s effective tax rate (controlling interest) for the three months ended September 30, 2024 was lower than the marginal tax rate of 24.5%, primarily due to tax windfalls attributable to share-based compensation. The Company’s effective tax rate (controlling interest) for the nine months ended September 30, 2024 was higher than the marginal tax rate of 24.5%, primarily due to an expense to reduce the carrying value of an Affiliate to fair value for which no tax benefit was recorded. The Company’s effective tax rate reflects the relative contributions of earnings in the jurisdictions in which the Company and its Affiliates operate and is impacted by changes in the jurisdictional mix of income before taxes. The Company continues to monitor and evaluate legislative developments related to the Organization for Economic Co- operation and Development’s Pillar Two directive (“Pillar Two”), which establishes a framework for a global minimum corporate tax rate of 15%. Several countries in which the Company or its Affiliates operate have adopted legislation to implement Pillar Two and several others are expected to enact similar rules in the future. The Company currently does not expect Pillar Two to have a material impact on its Consolidated Financial Statements.

Earnings Per Share

Earnings Per Share	9 Months Ended
Earnings Per Share	Sep. 30, 2024
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The calculation of Earnings per share (basic) is based on the weighted average number of shares of the Company’s common stock outstanding during the period. Earnings per share (diluted) is similar to Earnings per share (basic), but adjusts for the dilutive effect of the potential issuance of incremental shares of the Company’s common stock. The following is a reconciliation of the numerator and denominator used in the calculation of basic and diluted earnings per share available to common stockholders: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Numerator Net income (controlling interest) $ 217.0 $ 123.6 $ 476.8 $ 349.5 Income from hypothetical settlement of Redeemable non-controlling interests, net of taxes 17.1 5.2 39.4 1.0 Interest expense on junior convertible securities, net of taxes 3.4 3.4 10.1 10.1 Net income (controlling interest), as adjusted $ 237.5 $ 132.2 $ 526.3 $ 360.6 Denominator Average shares outstanding (basic) 34.9 30.1 35.6 31.4 Effect of dilutive instruments: Stock options and restricted stock units 1.7 1.7 1.7 1.9 Hypothetical issuance of shares to settle Redeemable non-controlling interests 5.1 1.5 3.9 0.2 Junior convertible securities 1.7 1.7 1.7 1.7 Average shares outstanding (diluted) 43.4 35.0 42.9 35.2 Average shares outstanding (diluted) in the table above excludes stock options and restricted stock units that have not met certain performance conditions and instruments that have an anti-dilutive effect on Earnings per share (diluted). The following is a summary of items excluded from the denominator in the table above: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Stock options and restricted stock units 0.2 0.2 0.3 0.2 Shares issuable to settle Redeemable non-controlling interests 0.1 2.3 0.7 3.6 For the three and nine months ended September 30, 2024 , under its authorized share repurchase programs, the Company repurchased 0.6 million and 3.6 million shares of its common stock at an average price per share of $163.23 and $158.62 , respectively.

Comprehensive Income

Comprehensive Income	9 Months Ended
Comprehensive Income	Sep. 30, 2024
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Comprehensive Income	Comprehensive Income The following table presents the tax effects allocated to each component of Other comprehensive income (loss) : For the Three Months Ended September 30, 2023 2024 Pre-Tax Tax (Expense) Benefit Net of Tax Pre-Tax Tax Benefit Net of Tax Foreign currency translation gain (loss) $ (27.6) $ (3.0) $ (30.6) $ 38.6 $ 0.6 $ 39.2 Change in net realized and unrealized gain (loss) on derivative financial instruments (0.3) 0.0 (0.3) 1.0 — 1.0 Change in net unrealized gain (loss) on available-for-sale debt securities 0.6 0.0 0.6 0.0 — 0.0 Other comprehensive income (loss) $ (27.3) $ (3.0) $ (30.3) $ 39.6 $ 0.6 $ 40.2 For the Nine Months Ended September 30, 2023 2024 Pre-Tax Tax (Expense) Benefit Net of Tax Pre-Tax Tax Expense Net of Tax Foreign currency translation gain $ 27.5 $ (6.9) $ 20.6 $ 44.8 $ (2.2) $ 42.6 Change in net realized and unrealized gain (loss) on derivative financial instruments 0.5 0.0 0.5 1.4 — 1.4 Change in net unrealized gain (loss) on available-for-sale debt securities 0.3 0.1 0.4 0.5 (0.1) 0.4 Other comprehensive income $ 28.3 $ (6.8) $ 21.5 $ 46.7 $ (2.3) $ 44.4 The components of accumulated other comprehensive loss, net of taxes, were as follows: Foreign Currency Translation Adjustment Realized and Unrealized Gains (Losses) on Derivative Financial Instruments Unrealized Gains (Losses) on Investment Available-for- Sale Debt Securities Total Balance, as of December 31, 2023 $ (255.3) $ (0.1) $ (0.5) $ (255.9) Other comprehensive income before reclassifications 42.6 0.8 0.4 43.8 Amounts reclassified — 0.6 — 0.6 Net other comprehensive income 42.6 1.4 0.4 44.4 Balance, as of September 30, 2024 $ (212.7) $ 1.3 $ (0.1) $ (211.5)

Accounting Standards and Poli_2

Accounting Standards and Policies (Policies)	9 Months Ended
Accounting Standards and Policies (Policies)	Sep. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation	The Consolidated Financial Statements of Affiliated Managers Group, Inc. (“AMG” or the “Company”) have been prepared in accordance with accounting principles generally accepted in the U.S. (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for full year financial statements. In the opinion of management, all normal and recurring adjustments considered necessary for a fair statement of the Company’s interim financial position and results of operations have been included and all intercompany balances and transactions have been eliminated. Operating results for interim periods are not necessarily indicative of the results that may be expected for any other period or for the full year. The Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2023 includes additional information about its operations, financial position, and accounting policies, and should be read in conjunction with this Quarterly Report on Form 10-Q. All amounts in these notes, except per share data in the text and tables herein, are stated in millions unless otherwise indicate d .
Use of Estimates	The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions
Recently Adopted Accounting Standards and Recent Accounting Developments	Recently Adopted Accounting Standards Effective January 1, 2024, the Company adopted Accounting Standard Update (“ASU”) 2022-03, Fair Value Measurement (Topic 820): Fair Value Measurement of Equity Securities Subject to Contractual Sale Restrictions. The adoption of this standard did not have a material impact on the Company’s Consolidated Financial Statements. Recent Accounting Developments In November 2023, the Financial Accounting Standards Board (“FASB”) issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires disclosure of incremental segment information on an annual and interim basis for all public entities to enable investors to develop more decision-useful financial analyses. The standard is effective for annual periods beginning after December 15, 2023 and for interim periods beginning after December 15, 2024. The Company currently does not expect the adoption to have a material impact on its Consolidated Financial Statements. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which requires greater disaggregation of income tax disclosures related to the income tax rate reconciliation and income taxes paid. The standard is effective for annual periods beginning after December 15, 2024. The Company currently does not expect the adoption to have a material impact on its Consolidated Financial Statements. In March 2024, the FASB issued ASU 2024-01, Compensation—Stock Compensation (Topic 718): Scope Application of Profits Interest and Similar Awards, which clarifies how an entity should apply the scope guidance to determine whether profits interest and similar awards should be accounted for in accordance with Topic 718. The standard is effective for interim and annual periods beginning after December 15, 2024 for the Company, and is effective for interim and annual periods beginning after December 15, 2025 for the Company’s Affiliates. The Company currently does not expect the adoption to have a material impact on its Consolidated Financial Statements.
Investments in Affiliates and Affiliate Sponsored Investments Products	Investments in Affiliates and Affiliate Sponsored Investment Products In evaluating whether an investment must be consolidated, the Company evaluates the risk, rewards, and significant terms of each of its Affiliates and other investments to determine if an investment is considered a voting rights entity (“VRE”) or a variable interest entity (“VIE”). An entity is a VRE when the total equity investment at risk is sufficient to enable the entity to finance its activities independently, and when the equity holders have the obligation to absorb losses, the right to receive residual returns, and the right to direct the activities of the entity that most significantly impact its economic performance. An entity is a VIE when it lacks one or more of the characteristics of a VRE, which, for the Company, are Affiliate investments structured as partnerships (or similar entities) where the Company is a limited partner and lacks substantive kick-out or substantive participation rights over the general partner. Assessing whether an entity is a VRE or VIE involves judgment. Upon the occurrence of certain events, management reviews and reconsiders its previous conclusion regarding the status of an entity as a VRE or a VIE. The Company consolidates VREs when it has control over significant operating, financial, and investing decisions of the entity. When the Company lacks such control, but is deemed to have significant influence, the Company accounts for the VRE under the equity method. Investments with readily determinable fair values in which the Company does not have rights to exercise significant influence are recorded at fair value on the Consolidated Balance Sheets, with changes in fair value included in Investment and other income. The Company consolidates VIEs when it is the primary beneficiary of the entity, which is defined as having the power to direct the activities that most significantly impact the VIE’s economic performance and the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to the VIE. Substantially all of the Company’s consolidated Affiliates considered VIEs are controlled because the Company holds a majority of the voting interests or it is the managing member or general partner. Furthermore, an Affiliate’s assets can be used for purposes other than the settlement of the respective Affiliate’s obligations. The Company applies the equity method of accounting to VIEs where the Company is not the primary beneficiary, but has the ability to exercise significant influence over operating and financial matters of the VIE. Investments in Affiliates Substantially all of the Company’s Affiliates are considered VIEs and are either consolidated or accounted for under the equity method. A limited number of the Company’s Affiliates are considered VREs and most of these are accounted for under the equity method. When an Affiliate is consolidated, the portion of the earnings attributable to Affiliate management’s and any co-investor’s equity ownership is included in Net income (non-controlling interests) in the Consolidated Statements of Income. Undistributed earnings attributable to Affiliate management’s and any co-investor’s equity ownership, along with their share of any tangible or intangible net assets, are included in Non-controlling interests on the Consolidated Balance Sheets. Affiliate equity interests where the holder has certain rights to demand settlement are presented, at their current redemption values, as Redeemable non-controlling interests or Other liabilities on the Consolidated Balance Sheets. The Company periodically issues, sells, and purchases the equity of its consolidated Affiliates. Because these transactions take place between entities that are under common control, any gains or losses attributable to these transactions are required to be included in Additional paid- in capital in the Consolidated Balance Sheets, net of any related income tax effects in the period the transaction occurs. When an Affiliate is accounted for under the equity method, the Company’s share of an Affiliate’s earnings or losses, net of amortization and impairments, is included in Equity method income (net) in the Consolidated Statements of Income and the carrying value of the Affiliate is recorded in Equity method investments in Affiliates (net) in the Consolidated Balance Sheets. The Company periodically performs assessments to determine if the fair value of an investment may have declined below its related carrying value for its Affiliates accounted for under the equity method for a period that the Company considers to be other-than-temporary. The Company performs these assessments if certain triggering events occur or annually during the fourth quarter. The Company first considers whether certain qualitative factors indicate an increased likelihood of a decline in the fair value of an Affiliate during the reporting period. If such a decline is identified, and it is likely that an investment’s fair value may have declined below its carrying value, the Company performs a quantitative assessment to determine if an impairment exists. Impairments are recorded as an expense in Equity method income (net) to reduce the carrying value of the Affiliate to fair value. Affiliate Sponsored Investment Products The Company’s Affiliates sponsor various investment products where the Affiliate also acts as the investment adviser. These investment products are typically owned primarily by third-party investors; however, certain products are funded with general partner and seed capital investments from the Company and its Affiliates. Third-party investors in Affiliate sponsored investment products are generally entitled to substantially all of the economics of these products, except for the asset- and performance-based fees earned by the Company’s Affiliates or any gains or losses attributable to the Company’s or its Affiliates’ investments in these products. As a result, the Company generally does not consolidate these products. However, for certain products, the Company’s consolidated Affiliates, as the investment manager, have the power to direct the activities of the investment product and have an exposure to the economics of the VIE that is more than insignificant, though generally only for a short period while the product is established and has yet to attract significant third-party investors. When the products are consolidated, the Company retains the specialized investment company accounting principles of the underlying products, and all of the underlying investments are carried at fair value in Investments in marketable securities, with corresponding changes in the investments’ fair values included in Investment and other income. Purchases and sales of securities are included in purchases and sales by consolidated Affiliate sponsored investment products in the Consolidated Statements of Cash Flows, respectively, and the third-party investors’ interests are recorded in Redeemable non-controlling interests. When the Company or its consolidated Affiliates no longer control these products, due to a reduction in ownership or other reasons, the products are deconsolidated with only the Company’s or its consolidated Affiliate’s investment in the product reported from the date of deconsolidation. The Company’s carrying value and maximum exposure to loss from unconsolidated Affiliate sponsored investment products, is its or its consolidated Affiliates’ interests in the unconsolidated net assets of the respective products.

Investments in Marketable Sec_2

Investments in Marketable Securities (Tables)	9 Months Ended
Investments in Marketable Securities (Tables)	Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Schedule of Investments in Marketable Securities	The following table summarizes the cost, gross unrealized gains, gross unrealized losses, and fair value of investments in equity securities: December 31, 2023 September 30, 2024 Cost $ 35.3 $ 37.6 Unrealized gains 2.6 4.7 Unrealized losses (0.0) (0.3) Fair value $ 37.9 $ 42.0 The following table summarizes the cost, gross unrealized gains, gross unrealized losses, and fair value of investments in U.S. Treasury securities classified as available-for-sale, all of which matured during the nine months ended September 30, 2024 , and consolidated Affiliate sponsored investment products classified as trading: Available-for-Sale Trading December 31, 2023 September 30, 2024 December 31, 2023 September 30, 2024 Cost $ 405.4 $ — $ 17.9 $ 23.3 Unrealized gains 0.0 — — 0.8 Unrealized losses (0.1) — (0.1) — Fair value $ 405.3 $ — $ 17.8 $ 24.1

Other Investments (Tables)

Other Investments (Tables)	9 Months Ended
Other Investments (Tables)	Sep. 30, 2024
Investments, All Other Investments [Abstract]
Schedule of Other Investments and Unfunded Commitments	The following table summarizes the fair values of these investments and any related unfunded commitments: December 31, 2023 September 30, 2024 Fair Value Unfunded Commitments Fair Value Unfunded Commitments Private equity funds (1) $ 424.4 $ 187.2 $ 477.5 $ 215.7 Investments in other strategies (2) 6.1 — 4.9 — Total (3) $ 430.5 $ 187.2 $ 482.4 $ 215.7 ___________________________ (1) The Company accounts for the majority of its interests in private equity funds one quarter in arrears (adjusted for current period calls and distributions). These funds primarily invest in a broad range of third-party funds and direct investments. Distributions will be received as the underlying assets are liquidated over the life of the funds, which is generally up to 15 years . (2) These are multi-disciplinary funds that invest across various asset classes and strategies, including equity and credit. Investments are generally redeemable on a daily, monthly, or quarterly basis. (3) Fair value attributable to the controlling interest was $324.9 million and $363.4 million as of December 31, 2023 and September 30, 2024 , respectively.
Schedule of Investments without Readily Determinable Fair Value	The following table summarizes the cost, cumulative unrealized gains, and carrying amount of investments without readily determinable fair values: December 31, 2023 September 30, 2024 Cost $ 8.5 $ 8.5 Cumulative unrealized gains 41.9 41.9 Carrying amount $ 50.4 $ 50.4 The following table presents the changes in Other investments: For the Three Months Ended September 30, 2023 2024 Measured at NAV as a Practical Expedient Without Readily Determinable Fair Values Total Measured at NAV as a Practical Expedient Without Readily Determinable Fair Values Total Balance, beginning of period $ 406.6 $ 50.4 $ 457.0 $ 479.9 $ 50.4 $ 530.3 Purchases and commitments 16.0 — 16.0 13.6 — 13.6 Sales and distributions (20.5) — (20.5) (20.4) — (20.4) Net realized and unrealized gains 5.4 — 5.4 9.3 — 9.3 Balance, end of period $ 407.5 $ 50.4 $ 457.9 $ 482.4 $ 50.4 $ 532.8 For the Nine Months Ended September 30, 2023 2024 Measured at NAV as a Practical Expedient Without Readily Determinable Fair Values Total Measured at NAV as a Practical Expedient Without Readily Determinable Fair Values Total Balance, beginning of period $ 371.2 $ 50.4 $ 421.6 $ 430.5 $ 50.4 $ 480.9 Purchases and commitments 62.0 — 62.0 78.1 — 78.1 Sales and distributions (49.4) — (49.4) (47.1) — (47.1) Net realized and unrealized gains 23.7 — 23.7 20.9 — 20.9 Balance, end of period $ 407.5 $ 50.4 $ 457.9 $ 482.4 $ 50.4 $ 532.8

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
Fair Value Measurements (Tables)	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Assets and Liabilities Measured on a Recurring Basis	The following tables summarize financial assets and liabilities that are measured at fair value on a recurring basis: Fair Value Measurements December 31, 2023 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets Investments in equity securities (1) $ 37.9 $ 37.9 $ — $ — Investments in debt securities (1) 423.1 — 423.1 — Financial Liabilities (2) Contingent payment obligations $ 14.7 $ — $ — $ 14.7 Affiliate equity purchase obligations 53.9 — — 53.9 Fair Value Measurements September 30, 2024 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Financial Assets Investments in equity securities (1) $ 42.0 $ 42.0 $ — $ — Investments in debt securities (1) 24.1 — 24.1 — Financial Liabilities (2) Contingent payment obligations $ 6.5 $ — $ — $ 6.5 Affiliate equity purchase obligations 58.9 — — 58.9 ___________________________ (1) Amounts are recorded in Investments in marketable securities on the Consolidated Balance Sheets. (2) Amounts are recorded in Other liabilities on the Consolidated Balance Sheets.
Schedule of Changes in Level 3 Assets and Liabilities for Affiliate Equity Repurchase Obligation	The following table presents the changes in Level 3 liabilities: For the Three Months Ended September 30, 2023 2024 Contingent Payment Obligations Affiliate Equity Purchase Obligations Contingent Payment Obligations Affiliate Equity Purchase Obligations Balance, beginning of period $ 23.4 $ 68.4 $ 7.9 $ 53.9 Purchases and issuances (1) — 4.7 — 10.1 Settlements and reductions — (25.4) — (5.0) Net realized and unrealized gains (2) (5.2) (2.5) (1.4) (0.1) Balance, end of period $ 18.2 $ 45.2 $ 6.5 $ 58.9 Net change in unrealized (gains) losses relating to instruments still held at the reporting date (1) $ (5.2) $ (2.4) $ (1.4) $ (0.5) For the Nine Months Ended September 30, 2023 2024 Contingent Payment Obligations Affiliate Equity Purchase Obligations Contingent Payment Obligations Affiliate Equity Purchase Obligations Balance, beginning of period $ 21.0 $ 24.5 $ 14.7 $ 53.9 Purchases and issuances (1) — 75.7 — 66.3 Settlements and reductions — (49.7) — (62.1) Net realized and unrealized (gains) losses (2) (2.8) (5.3) (8.2) 0.8 Balance, end of period $ 18.2 $ 45.2 $ 6.5 $ 58.9 Net change in unrealized (gains) losses relating to instruments still held at the reporting date (1) $ (2.8) $ (4.5) $ (8.2) $ 0.4 ___________________________ (1) Affiliate equity purchase obligation activity includes transfers from Redeemable non-controlling interests. (2) Gains and losses resulting from changes to expected payments are included in Other expenses (net) in the Consolidated Statements of Income and the accretion of these obligations is included in Interest expense in the Consolidated Statements of Income.
Schedule of Quantitative Information used in Valuing Level 3 Liabilities	The following table presents certain quantitative information about the significant unobservable inputs used in valuing the Company’s Level 3 fair value measurements: Quantitative Information About Level 3 Fair Value Measurements December 31, 2023 September 30, 2024 Valuation Techniques Unobservable Input Fair Value Range Weighted Average (1) Fair Value Range Weighted Average (1) Contingent payment obligations Monte Carlo Simulation Volatility $ 14.7 19% - 25% 21 % $ 6.5 10% - 18% 11 % Discount rates 6% 6 % 5% 5 % Affiliate equity purchase obligations Discounted cash flow Growth rates (2) $ 53.9 (6)% - 7% 1 % $ 58.9 (5)% - 8% 0 % Discount rates 14% - 17% 14 % 14% - 18% 15 % ___________________________ (1) Calculated by comparing the relative fair value of an obligation to its respective total. (2) Represents growth rates of asset- and performance-based fees.
Schedule of Other Financial Assets and Liabilities Not Carried at Fair Value	The following table summarizes the Company’s other financial liabilities not carried at fair value: December 31, 2023 September 30, 2024 Carrying Value Fair Value Carrying Value Fair Value Fair Value Hierarchy Senior notes $ 1,099.4 $ 1,049.8 $ 1,097.3 $ 1,075.8 Level 2 Junior subordinated notes 765.9 612.0 1,216.0 1,129.6 Level 2 Junior convertible securities 341.7 340.9 341.7 375.9 Level 2

Investments in Affiliates and_2

Investments in Affiliates and Affiliate Sponsored Investment Products (Tables)	9 Months Ended
	Sep. 30, 2024
Variable Interest Entities [Abstract]
Schedule of Unconsolidated Assets and Liabilities of Equity Method Investments and Company's Risk of Loss	The unconsolidated assets, net of liabilities and non-controlling interests of Affiliates accounted for under the equity method considered VIEs, and the Company’s carrying value and maximum exposure to loss, were as follows: December 31, 2023 September 30, 2024 Unconsolidated VIE Net Assets Carrying Value and Maximum Exposure to Loss Unconsolidated VIE Net Assets Carrying Value and Maximum Exposure to Loss Affiliates accounted for under the equity method $ 1,492.4 $ 2,198.2 $ 1,173.6 $ 2,042.7 The net assets of unconsolidated VIEs attributable to Affiliate sponsored investment products, and the Company’s carrying value and maximum exposure to loss, were as follows: December 31, 2023 September 30, 2024 Unconsolidated VIE Net Assets Carrying Value and Maximum Exposure to Loss Unconsolidated VIE Net Assets Carrying Value and Maximum Exposure to Loss Affiliate sponsored investment products $ 5,788.3 $ 29.8 $ 5,332.2 $ 24.4

Debt (Tables)

Debt (Tables)	9 Months Ended
Debt (Tables)	Sep. 30, 2024
Debt Disclosure [Abstract]
Schedule of Debt	The following table summarizes the Company’s Debt: December 31, 2023 September 30, 2024 Senior bank debt $ 349.9 $ — Senior notes 1,096.9 1,091.7 Junior subordinated notes 751.8 1,189.0 Junior convertible securities 338.9 339.0 Debt $ 2,537.5 $ 2,619.7
Schedule of Principal Terms of Senior and Junior Subordinated Notes	The principal terms of the senior notes outstanding as of September 30, 2024 are presented and described below: 2025 Senior Notes 2030 Senior Notes 2034 Senior Notes Issue date February 2015 June 2020 August 2024 Maturity date August 2025 June 2030 August 2034 Par value (in millions) $ 350.0 $ 350.0 $ 400.0 Stated coupon 3.50 % 3.30 % 5.50 % Coupon frequency Semi-annually Semi-annually Semi-annually Call price As defined As defined As defined As of September 30, 2024 , the Company had junior subordinated notes outstanding, the respective principal terms of which are presented and described below: 2059 Junior Subordinated Notes 2060 Junior Subordinated Notes 2061 Junior Subordinated Notes 2064 Junior Subordinated Notes Issue date March 2019 September 2020 July 2021 March 2024 Maturity date March 2059 September 2060 September 2061 March 2064 Par value (in millions) $ 300.0 $ 275.0 $ 200.0 $ 450.0 Stated coupon 5.875 % 4.75 % 4.20 % 6.75 % Coupon frequency Quarterly Quarterly Quarterly Quarterly Call price As defined As defined As defined As defined NYSE Symbol MGR MGRB MGRD MGRE
Schedule of Convertible Securities	The following table presents interest expense recorded in connection with the junior convertible securities: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Contractual interest expense $ 4.4 $ 4.4 $ 13.2 $ 13.2 Amortization of debt issuance costs 0.1 0.1 0.2 0.2 Total $ 4.5 $ 4.5 $ 13.4 $ 13.4 Effective interest rate 5.21 % 5.21 % 5.21 % 5.21 %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
Commitments and Contingencies (Tables)	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Schedule of Business Acquisitions by Acquisition, Contingent Consideration	As of September 30, 2024 , the Company was obligated to make deferred payments and was contingently liable to make payments in connection with certain of its consolidated Affiliates, which are included in Other liabilities, as follows: Earliest Payable Controlling Interest Co-Investor Total 2024 2025 Deferred payment obligations $ 43.3 $ — $ 43.3 $ 21.7 $ 21.6 Contingent payment obligations (1) 6.4 0.1 6.5 — 6.5 ___________________________ (1) Fair value as of September 30, 2024 . The Company is contingently liable to make maximum contingent payments of up to $110.0 million ( $24.9 million attributable to the co-investor), all of which may become payable in 2025.

Goodwill and Acquired Client _2

Goodwill and Acquired Client Relationships (Tables)	9 Months Ended
Goodwill and Acquired Client Relationships (Tables)	Sep. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in Goodwill	The following table presents the changes in the Company’s consolidated Goodwill: Goodwill Balance, as of December 31, 2023 $ 2,523.6 Foreign currency translation 8.4 Balance, as of September 30, 2024 $ 2,532.0 As of September 30, 2024 the Company completed its annual impairment assessment on goodwill and no impairment was indicated.
Schedule of Changes in the Components of Acquired Client Relationships	The following table presents the changes in the Company’s components of Acquired client relationships (net): Acquired Client Relationships (Net) Definite-lived Indefinite-lived Total Gross Book Value Accumulated Amortization Net Book Value Net Book Value Net Book Value Balance, as of December 31, 2023 $ 1,260.5 $ (1,051.2) $ 209.3 $ 1,603.1 $ 1,812.4 Intangible amortization and impairments — (21.8) (21.8) — (21.8) Foreign currency translation 4.0 (4.0) — 16.5 16.5 Balance, as of September 30, 2024 $ 1,264.5 $ (1,077.0) $ 187.5 $ 1,619.6 $ 1,807.1

Equity Method Investments in _2

Equity Method Investments in Affiliates (Tables)	9 Months Ended
Equity Method Investments in Affiliates (Tables)	Sep. 30, 2024
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Changes in Equity Method Investments in Affiliates	Equity method investments in Affiliates (net) consisted of the following: December 31, 2023 September 30, 2024 Goodwill $ 1,323.3 $ 1,348.1 Definite-lived acquired client relationships (net) 652.5 568.1 Indefinite-lived acquired client relationships (net) 122.6 122.4 Undistributed earnings and tangible capital 190.1 109.8 Equity method investments in Affiliates (net) $ 2,288.5 $ 2,148.4 The following table presents the changes in Equity method investments in Affiliates (net): Equity Method Investments in Affiliates (Net) Balance, as of December 31, 2023 $ 2,288.5 Investments in Affiliates 12.3 Earnings 292.6 Intangible amortization and impairments (104.3) Distributions of earnings (357.3) Foreign currency translation 16.6 Balance, as of September 30, 2024 $ 2,148.4

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
Share-Based Compensation (Tables)	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Schedule of Share-Based Compensation	The following table presents share-based compensation expense: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Share-based compensation expense $ 14.5 $ 10.2 $ 43.9 $ 42.1 Tax benefit 1.9 1.2 5.5 5.2
Schedule of Company Restricted Stock Units Transactions	The following table summarizes transactions in the Company’s restricted stock units: Restricted Stock Units Weighted Average Grant Date Value Unvested units—December 31, 2023 0.9 $ 138.51 Units granted 0.2 159.32 Units vested (0.3) 129.72 Units forfeited (0.0) 149.00 Performance condition changes 0.0 154.72 Unvested units—September 30, 2024 0.8 147.40
Schedule of Company Stock Option Transactions	The following table summarizes transactions in the Company’s stock options: Stock Options Weighted Average Exercise Price Weighted Average Remaining Contractual Life (Years) Unexercised options outstanding—December 31, 2023 3.2 $ 76.74 Options granted — — Options exercised (1.3) 74.82 Options forfeited (0.0) 185.98 Options expired (0.0) 152.36 Performance condition changes 0.0 129.17 Unexercised options outstanding—September 30, 2024 1.9 78.02 2.1 Exercisable at September 30, 2024 1.5 75.89 1.9

Redeemable Non-Controlling In_2

Redeemable Non-Controlling Interests (Tables)	9 Months Ended
Redeemable Non-Controlling Interests (Tables)	Sep. 30, 2024
Noncontrolling Interest [Abstract]
Schedule of Changes in Redeemable Non-Controlling Interests	The following table presents the changes in Redeemable non-controlling interests: Redeemable Non-controlling Interests Balance, as of December 31, 2023 (1) $ 393.4 Increase attributable to consolidated Affiliate sponsored investment products 1.5 Transfers to Other liabilities (42.2) Transfers from Non-controlling interests 1.7 Changes in redemption value 42.7 Balance, as of September 30, 2024 (1) $ 397.1 ___________________________ (1) As of December 31, 2023 and September 30, 2024 , Redeemable non-controlling interests include consolidated Affiliate sponsored investment products primarily attributable to third-party investors of $11.8 million and $13.3 million , respectively.

Affiliate Equity (Tables)

Affiliate Equity (Tables)	9 Months Ended
Affiliate Equity (Tables)	Sep. 30, 2024
Affiliate Equity [Abstract]
Schedule of Affiliate Equity Compensation	The following table presents Affiliate equity compensation expense: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Controlling interest $ 0.0 $ 2.4 $ 6.1 $ 15.6 Non-controlling interests 11.5 9.7 33.4 30.9 Total $ 11.5 $ 12.1 $ 39.5 $ 46.5
Schedule of Affiliate Equity Unrecognized Compensation Expense	The following table presents unrecognized Affiliate equity compensation expense: Controlling Interest Remaining Life Non-controlling Interests Remaining Life December 31, 2023 $ 30.6 5 years $ 235.7 6 years September 30, 2024 39.0 4 years 217.6 6 years
Schedule of Changes in the Company's Interest in its Affiliates on the Controlling Interest's Equity	While the Company presents the current redemption value of Affiliate equity within Redeemable non-controlling interests, with changes in the current redemption value increasing or decreasing the controlling interest’s equity over time, the following table presents the cumulative effect that ownership changes had on the controlling interest’s equity related only to Affiliate equity transactions that occurred during the applicable periods: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Net income (controlling interest) $ 217.0 $ 123.6 $ 476.8 $ 349.5 Decrease in controlling interest paid-in capital from Affiliate equity issuances (4.5) — (13.1) (2.6) Increase (decrease) in controlling interest paid-in capital from Affiliate equity purchases 1.9 (0.5) (36.1) (22.9) Net income (controlling interest) including the net impact of Affiliate equity transactions $ 214.4 $ 123.1 $ 427.6 $ 324.0

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
Income Taxes (Tables)	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Schedule of Income Tax Provisions by Controlling and Noncontrolling Interests	The following table presents the consolidated provision for income taxes: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Controlling interest (1) $ 75.9 $ 29.5 $ 149.9 $ 123.7 Non-controlling interests 1.8 1.8 5.5 6.3 Income tax expense $ 77.7 $ 31.3 $ 155.4 $ 130.0 Income before income taxes (controlling interest) $ 292.9 $ 153.1 $ 626.7 $ 473.2 Effective tax rate (controlling interest) (2) 25.9 % 19.3 % 23.9 % 26.1 % ___________________________ (1) For the three months ended September 30, 2023 and 2024 , income tax expense (controlling interest) included intangible- related deferred tax (benefit) expense of $(13.5) million and $16.4 million , respectively. For the nine months ended September 30, 2023 and 2024 , income tax expense (controlling interest) included intangible-related deferred tax expense of $16.4 million and $50.6 million , respectively. (2) Taxes attributable to the controlling interest divided by income before income taxes (controlling interest ) .

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
Earnings Per Share (Tables)	Sep. 30, 2024
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Earnings (Loss) Per Share	The following is a reconciliation of the numerator and denominator used in the calculation of basic and diluted earnings per share available to common stockholders: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Numerator Net income (controlling interest) $ 217.0 $ 123.6 $ 476.8 $ 349.5 Income from hypothetical settlement of Redeemable non-controlling interests, net of taxes 17.1 5.2 39.4 1.0 Interest expense on junior convertible securities, net of taxes 3.4 3.4 10.1 10.1 Net income (controlling interest), as adjusted $ 237.5 $ 132.2 $ 526.3 $ 360.6 Denominator Average shares outstanding (basic) 34.9 30.1 35.6 31.4 Effect of dilutive instruments: Stock options and restricted stock units 1.7 1.7 1.7 1.9 Hypothetical issuance of shares to settle Redeemable non-controlling interests 5.1 1.5 3.9 0.2 Junior convertible securities 1.7 1.7 1.7 1.7 Average shares outstanding (diluted) 43.4 35.0 42.9 35.2
Schedule of Shares Excluded from Calculation of Basic and Diluted Earnings (Loss) Per Share	The following is a summary of items excluded from the denominator in the table above: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2023 2024 2023 2024 Stock options and restricted stock units 0.2 0.2 0.3 0.2 Shares issuable to settle Redeemable non-controlling interests 0.1 2.3 0.7 3.6

Comprehensive Income (Tables)

Comprehensive Income (Tables)	9 Months Ended
Comprehensive Income (Tables)	Sep. 30, 2024
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss)	The following table presents the tax effects allocated to each component of Other comprehensive income (loss) : For the Three Months Ended September 30, 2023 2024 Pre-Tax Tax (Expense) Benefit Net of Tax Pre-Tax Tax Benefit Net of Tax Foreign currency translation gain (loss) $ (27.6) $ (3.0) $ (30.6) $ 38.6 $ 0.6 $ 39.2 Change in net realized and unrealized gain (loss) on derivative financial instruments (0.3) 0.0 (0.3) 1.0 — 1.0 Change in net unrealized gain (loss) on available-for-sale debt securities 0.6 0.0 0.6 0.0 — 0.0 Other comprehensive income (loss) $ (27.3) $ (3.0) $ (30.3) $ 39.6 $ 0.6 $ 40.2 For the Nine Months Ended September 30, 2023 2024 Pre-Tax Tax (Expense) Benefit Net of Tax Pre-Tax Tax Expense Net of Tax Foreign currency translation gain $ 27.5 $ (6.9) $ 20.6 $ 44.8 $ (2.2) $ 42.6 Change in net realized and unrealized gain (loss) on derivative financial instruments 0.5 0.0 0.5 1.4 — 1.4 Change in net unrealized gain (loss) on available-for-sale debt securities 0.3 0.1 0.4 0.5 (0.1) 0.4 Other comprehensive income $ 28.3 $ (6.8) $ 21.5 $ 46.7 $ (2.3) $ 44.4
Schedule of Components of Accumulated Other Comprehensive Loss	The components of accumulated other comprehensive loss, net of taxes, were as follows: Foreign Currency Translation Adjustment Realized and Unrealized Gains (Losses) on Derivative Financial Instruments Unrealized Gains (Losses) on Investment Available-for- Sale Debt Securities Total Balance, as of December 31, 2023 $ (255.3) $ (0.1) $ (0.5) $ (255.9) Other comprehensive income before reclassifications 42.6 0.8 0.4 43.8 Amounts reclassified — 0.6 — 0.6 Net other comprehensive income 42.6 1.4 0.4 44.4 Balance, as of September 30, 2024 $ (212.7) $ 1.3 $ (0.1) $ (211.5)

Investments in Marketable Sec_3

Investments in Marketable Securities - Cost, Gross Unrealized Gains and Losses and Fair Value (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Cost	$ 37.6	$ 35.3
Unrealized gains	4.7	2.6
Unrealized losses	(0.3)	0
Fair value	$ 42	$ 37.9

Investments in Marketable Sec_4

Investments in Marketable Securities - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Marketable Securities [Line Items]
Net unrealized gain (loss)	$ 2	$ (2.1)	$ 3.5	$ 1.3
Proceeds from maturity of AFS securities	100	178.4	825.2	280.1
Purchase of available-for-sale securities	0	245.3	413.9	420.3
Debt securities, net unrealized gain	0.8	$ 0	1.4	$ 0
Variable Interest Entity, Primary Beneficiary
Marketable Securities [Line Items]
Fair value of deconsolidated investment in affiliate, equity securities	$ 11.9		$ 11.9		$ 15.8

Investments in Marketable Sec_5

Investments in Marketable Securities - Debt Securities, Available-for-Sale (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Available-for-Sale
Cost	$ 0	$ 405.4
Unrealized gains	0	0
Unrealized losses	0	(0.1)
Fair value	0	405.3
Trading
Cost	23.3	17.9
Unrealized gains	0.8	0
Unrealized losses	0	(0.1)
Fair value	$ 24.1	$ 17.8

Other Investments - Investments

Other Investments - Investments Measured at NAV as a Practical Expedient (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
NAV of investments at fair value
Unfunded Commitments	$ 215.7	$ 187.2
Life of funds (generally up to)	15 years
Private equity funds
NAV of investments at fair value
Unfunded Commitments	$ 215.7	187.2
Investments in other strategies
NAV of investments at fair value
Unfunded Commitments	0	0
Fair Value Measured at NAV
NAV of investments at fair value
Fair Value	482.4	430.5
Fair Value Measured at NAV \| Controlling Interest
NAV of investments at fair value
Fair Value	363.4	324.9
Fair Value Measured at NAV \| Private equity funds
NAV of investments at fair value
Fair Value	477.5	424.4
Fair Value Measured at NAV \| Investments in other strategies
NAV of investments at fair value
Fair Value	$ 4.9	$ 6.1

Other Investments - Investmen_2

Other Investments - Investments without Readily Determinable Fair Value (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Investments, All Other Investments [Abstract]
Cost	$ 8,500,000	$ 8,500,000		$ 8,500,000
Cumulative unrealized gains	41,900,000	41,900,000		41,900,000
Carrying amount	50,400,000	50,400,000	$ 50,400,000	$ 50,400,000	$ 50,400,000	$ 50,400,000	$ 50,400,000
Upward adjustments	0	0
Downward adjustments	$ 0	$ 0

Other Investments - Schedule of

Other Investments - Schedule of Changes in Other Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Other Investments [Roll Forward]
Balance, beginning of period	$ 530.3	$ 457	$ 480.9	$ 421.6
Purchases and commitments	13.6	16	78.1	62
Sales and distributions	(20.4)	(20.5)	(47.1)	(49.4)
Net realized and unrealized gains	9.3	5.4	20.9	23.7
Balance, end of period	532.8	457.9	532.8	457.9
Equity Securities Without Readily Determinable Fair Value [Roll Forward]
Balance, beginning of period	50.4	50.4	50.4	50.4
Purchases and commitments	0	0	0	0
Sales and distributions	0	0	0	0
Net realized and unrealized gains	0	0	0	0
Balance, end of period	50.4	50.4	50.4	50.4
Fair Value Measured at NAV
Other Investments [Roll Forward]
Balance, beginning of period	479.9	406.6	430.5	371.2
Purchases and commitments	13.6	16	78.1	62
Sales and distributions	(20.4)	(20.5)	(47.1)	(49.4)
Net realized and unrealized gains	9.3	5.4	20.9	23.7
Balance, end of period	$ 482.4	$ 407.5	$ 482.4	$ 407.5

Fair Value Measurements - Asset

Fair Value Measurements - Assets and Liabilities Measured on a Recurring Basis (Details) - Fair Value Measured on a Recurring Basis - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financial Assets
Investments in equity securities	$ 42	$ 37.9
Investments in debt securities	24.1	423.1
Financial Liabilities
Contingent payment obligations	6.5	14.7
Affiliate equity purchase obligations	58.9	53.9
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Assets
Investments in equity securities	42	37.9
Investments in debt securities	0	0
Financial Liabilities
Contingent payment obligations	0	0
Affiliate equity purchase obligations	0	0
Significant Other Observable Inputs (Level 2)
Financial Assets
Investments in equity securities	0	0
Investments in debt securities	24.1	423.1
Financial Liabilities
Contingent payment obligations	0	0
Affiliate equity purchase obligations	0	0
Significant Unobservable Inputs (Level 3)
Financial Assets
Investments in equity securities	0	0
Investments in debt securities	0	0
Financial Liabilities
Contingent payment obligations	6.5	14.7
Affiliate equity purchase obligations	$ 58.9	$ 53.9

Fair Value Measurements - Chang

Fair Value Measurements - Changes in Level 3 Liabilities (Details) - Significant Unobservable Inputs (Level 3) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Contingent Payment Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 7.9	$ 23.4	$ 14.7	$ 21
Purchases and issuances	0	0	0	0
Settlements and reductions	0	0	0	0
Net realized and unrealized (gains) losses	(1.4)	(5.2)	(8.2)	(2.8)
Balance, end of period	6.5	18.2	6.5	18.2
Net change in unrealized (gains) losses relating to instruments still held at the reporting date	(1.4)	(5.2)	(8.2)	(2.8)
Affiliate Equity Purchase Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	53.9	68.4	53.9	24.5
Purchases and issuances	10.1	4.7	66.3	75.7
Settlements and reductions	(5)	(25.4)	(62.1)	(49.7)
Net realized and unrealized (gains) losses	(0.1)	(2.5)	0.8	(5.3)
Balance, end of period	58.9	45.2	58.9	45.2
Net change in unrealized (gains) losses relating to instruments still held at the reporting date	$ (0.5)	$ (2.4)	$ 0.4	$ (4.5)

Fair Value Measurements - Quant

Fair Value Measurements - Quantitative Information used in Valuing Level 3 Liabilities (Details) - Significant Unobservable Inputs (Level 3) $ in Millions	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Contingent payment obligations \| Monte Carlo Simulation
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair Value	$ 6.5	$ 14.7
Contingent payment obligations \| Monte Carlo Simulation \| Volatility \| Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity purchase obligations, measurement input	0.10	0.19
Contingent payment obligations \| Monte Carlo Simulation \| Volatility \| Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity purchase obligations, measurement input	0.18	0.25
Contingent payment obligations \| Monte Carlo Simulation \| Volatility \| Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity purchase obligations, measurement input	0.11	0.21
Contingent payment obligations \| Monte Carlo Simulation \| Discount rates
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity purchase obligations, measurement input	0.05	0.06
Contingent payment obligations \| Monte Carlo Simulation \| Discount rates \| Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity purchase obligations, measurement input	0.05	0.06
Affiliate equity purchase obligations \| Discounted cash flow
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair Value	$ 58.9	$ 53.9
Affiliate equity purchase obligations \| Discounted cash flow \| Discount rates \| Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity purchase obligations, measurement input	0.14	0.14
Affiliate equity purchase obligations \| Discounted cash flow \| Discount rates \| Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity purchase obligations, measurement input	0.18	0.17
Affiliate equity purchase obligations \| Discounted cash flow \| Discount rates \| Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity purchase obligations, measurement input	0.15	0.14
Affiliate equity purchase obligations \| Discounted cash flow \| Growth rates \| Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity purchase obligations, measurement input	(0.05)	(0.06)
Affiliate equity purchase obligations \| Discounted cash flow \| Growth rates \| Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity purchase obligations, measurement input	0.08	0.07
Affiliate equity purchase obligations \| Discounted cash flow \| Growth rates \| Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity purchase obligations, measurement input	0	0.01

Fair Value Measurements - Other

Fair Value Measurements - Other Financial Assets and Liabilities Not Carried at Fair Value (Details) - Level 2 - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	$ 1,097.3	$ 1,099.4
Junior subordinated notes	1,216	765.9
Junior convertible securities	341.7	341.7
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	1,075.8	1,049.8
Junior subordinated notes	1,129.6	612
Junior convertible securities	$ 375.9	$ 340.9

Investments in Affiliates and_3

Investments in Affiliates and Affiliate Sponsored Investment Products - Affiliated Accounted For Under Equity Method (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Variable Interest Entities
Carrying value of equity method investment in affiliate	$ 2,148.4	$ 2,288.5
Carrying amount and maximum exposure to loss equity method investments considered VREs	105.7	90.3
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entities
Unconsolidated VIE Net Assets	1,173.6	1,492.4
Carrying Value and Maximum Exposure to Loss	$ 2,042.7	$ 2,198.2

Investments in Affiliates and_4

Investments in Affiliates and Affiliate Sponsored Investment Products - Affiliated Sponsored Investment Products (Details) - Variable Interest Entity, Primary Beneficiary - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Variable Interest Entities
Unconsolidated VIE Net Assets	$ 5,332.2	$ 5,788.3
Carrying Value and Maximum Exposure to Loss	$ 24.4	$ 29.8

Debt - Schedule of Debt (Detail

Debt - Schedule of Debt (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Debt	$ 2,619.7	$ 2,537.5
Senior bank debt
Debt Instrument [Line Items]
Debt	0	349.9
Senior notes
Debt Instrument [Line Items]
Debt	1,091.7	1,096.9
Junior subordinated notes
Debt Instrument [Line Items]
Debt	1,189	751.8
Junior convertible securities
Debt Instrument [Line Items]
Debt	$ 339	$ 338.9

Debt - Senior Bank Debt (Detail

Debt - Senior Bank Debt (Details) - USD ($)	9 Months Ended
Debt - Senior Bank Debt (Details) - USD ($)	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Debt Instrument [Line Items]
Repayments of long-term debt	$ 750,000,000	$ 25,000,000
Term Loan \| Senior bank debt
Debt Instrument [Line Items]
Repayments of long-term debt	$ 350,000,000
Basis spread on debt variable rate	0.10%
Term Loan \| Senior bank debt \| Debt Instrument, Adjustment Rate
Debt Instrument [Line Items]
Basis spread on debt variable rate	0.10%
Term Loan \| Senior bank debt \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Basis spread on debt variable rate	0.85%
Revolver \| Senior bank debt
Debt Instrument [Line Items]
Available borrowing	$ 1,250,000,000
Additional borrowing amount	500,000,000
Borrowings outstanding	$ 0		$ 0

Debt - Schedule of Principal Te

Debt - Schedule of Principal Terms of Senior and Junior Subordinated Notes (Details) - USD ($) $ in Millions	Sep. 30, 2024	Aug. 20, 2024	Mar. 20, 2024
Senior notes \| 2025 Senior Notes
Debt Instrument [Line Items]
Par value	$ 350
Stated coupon	3.50%
Senior notes \| 2030 Senior Notes
Debt Instrument [Line Items]
Par value	$ 350
Stated coupon	3.30%
Senior notes \| 2034 Senior Notes
Debt Instrument [Line Items]
Par value	$ 400	$ 400
Stated coupon	5.50%
Junior subordinated notes \| 2059 Junior Subordinated Notes
Debt Instrument [Line Items]
Par value	$ 300
Stated coupon	5.875%
Junior subordinated notes \| 2060 Junior Subordinated Notes
Debt Instrument [Line Items]
Par value	$ 275
Stated coupon	4.75%
Junior subordinated notes \| 2061 Junior Subordinated Notes
Debt Instrument [Line Items]
Par value	$ 200
Stated coupon	4.20%
Junior subordinated notes \| 2064 Junior Subordinated Notes
Debt Instrument [Line Items]
Par value	$ 450		$ 450
Stated coupon	6.75%

Debt - Senior Notes and Junior

Debt - Senior Notes and Junior Subordinated Notes (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2024	Sep. 30, 2024	Sep. 30, 2023	Aug. 20, 2024	Mar. 20, 2024
Debt Instrument [Line Items]
Repayments of long-term debt		$ 750	$ 25
Junior subordinated notes \| On or after March 30, 2029
Debt Instrument [Line Items]
Redemption price percentage		100%
Junior subordinated notes \| If changes in tax laws and interpretations occur
Debt Instrument [Line Items]
Redemption price percentage		100%
Junior subordinated notes \| If a rating agency makes certain changes relating to the equity credit criteria for securities
Debt Instrument [Line Items]
Redemption price percentage		102%
4.25% senior notes \| Senior notes
Debt Instrument [Line Items]
Repayments of long-term debt	$ 400
Debt interest rate	4.25%
2034 Senior Notes \| Senior notes
Debt Instrument [Line Items]
Debt interest rate		5.50%
Face amount		$ 400		$ 400
Redemption price percentage		100%
2025 Senior Notes \| Senior notes
Debt Instrument [Line Items]
Debt interest rate		3.50%
Face amount		$ 350
Redemption price percentage		100%
Applicable basis spread over redemption price percentage		0.25%
2030 Senior Notes \| Senior notes
Debt Instrument [Line Items]
Debt interest rate		3.30%
Face amount		$ 350
Redemption price percentage		100%
Applicable basis spread over redemption price percentage		0.40%
6.750% Junior Subordinated Notes due 2064 \| Junior subordinated notes
Debt Instrument [Line Items]
Debt interest rate		6.75%
Face amount		$ 450			$ 450
6.750% Junior Subordinated Notes due 2064 \| Junior subordinated notes \| On or after March 30, 2029
Debt Instrument [Line Items]
Redemption price percentage		100%

Debt - Junior Convertible Secur

Debt - Junior Convertible Securities (Details) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2024 USD ($) d $ / shares	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
Debt	$ 2,619.7	$ 2,537.5
Junior convertible securities
Debt Instrument [Line Items]
Debt	339	338.9
Junior Convertible Trust Preferred Securities \| Junior convertible securities
Debt Instrument [Line Items]
Debt	$ 341.7
Debt interest rate	5.15%
Unamortized debt issuance costs	$ 2.7	$ 2.9
Conversion ratio per share of common stock	0.2558
Face amount of convertible security (in dollars per share) \| $ / shares	$ 50
Adjusted conversion price (in dollars per share) \| $ / shares	$ 195.47
Convertible debt, threshold trading days \| d	20
Convertible debt, threshold consecutive trading days \| d	30
Debt instrument, convertible, threshold percentage	1.30

Debt - Schedule of Convertible

Debt - Schedule of Convertible Securities (Details) - Junior Convertible Trust Preferred Securities - Junior convertible securities - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
Contractual interest expense	$ 4.4	$ 4.4	$ 13.2	$ 13.2
Amortization of debt issuance costs	0.1	0.1	0.2	0.2
Total	$ 4.5	$ 4.5	$ 13.4	$ 13.4
Effective interest rate	5.21%	5.21%	5.21%	5.21%

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	Sep. 30, 2024 USD ($)
Commitments and Contingencies
Co-investment commitments in partnership	$ 215.7
Deferred payment obligation	43.3
Equity Method Investee
Commitments and Contingencies
Deferred payment obligation	5.1
Payments for Achievement of Financial Targets
Commitments and Contingencies
Payment contingent on not meeting financial targets	12.5
Payment contingent on exercise of option to reduce ownership percentage	25
Payments for Achievement of Financial Targets \| Equity Method Investee
Commitments and Contingencies
Total contingent payments	243.1
Contingent payments in remainder of fiscal year	4
Contingent payments, 2025 through 2028	239.1
Payments For Contingent Financing
Commitments and Contingencies
Total contingent payments	$ 50

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Contingent Consideration (Details) $ in Millions	Sep. 30, 2024 USD ($)
Deferred payment obligations
Total	$ 43.3
2024	21.7
2025	21.6
Contingent payment obligations
Total	6.5
2024	0
2025	6.5
Co-Investor
Deferred payment obligations
Total	0
Contingent payment obligations
Total	0.1
Co-Investor \| Maximum
Contingent payment obligations
Total	24.9
Controlling Interest
Deferred payment obligations
Total	43.3
Contingent payment obligations
Total	6.4
Controlling Interest \| Maximum
Contingent payment obligations
Total	$ 110

Goodwill and Acquired Client _3

Goodwill and Acquired Client Relationships - Schedule of Changes in Goodwill (Details)	9 Months Ended
	Sep. 30, 2024 USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 2,523,600,000
Foreign currency translation	8,400,000
Ending balance	2,532,000,000
Goodwill impairment	$ 0

Goodwill and Acquired Client _4

Goodwill and Acquired Client Relationships - Schedule of Changes in the Components of Acquired Client Relationships (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Total
Beginning balance, Net Book Value			$ 1,812.4
Intangible amortization and impairments	$ (7.3)	$ (12.5)	(21.8)	$ (37.5)
Ending balance, Net Book Value	1,807.1		1,807.1
Acquired Client Relationships
Indefinite-lived
Beginning balance, Net Book Value			1,603.1
Foreign currency translation			16.5
Ending balance, Net Book Value	1,619.6		1,619.6
Total
Beginning balance, Net Book Value			1,812.4
Intangible amortization and impairments			21.8
Foreign currency translation			16.5
Ending balance, Net Book Value	1,807.1		1,807.1
Acquired Client Relationships
Definite-lived
Beginning balance, Gross Book Value			1,260.5
Beginning balance, Accumulated Amortization			(1,051.2)
Beginning balance, Net Book Value			209.3
Intangible amortization and impairments	(7.3)	$ (12.5)	(21.8)	$ (37.5)
Foreign currency translation, Gross Book Value			4
Foreign currency translation, Accumulated Amortization			(4)
Foreign currency translation, Net Book Value			0
Ending balance, Gross Book Value	1,264.5		1,264.5
Ending balance, Accumulated Amortization	(1,077)		(1,077)
Ending balance, Net Book Value	$ 187.5		$ 187.5

Goodwill and Acquired Client _5

Goodwill and Acquired Client Relationships - Additional Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Estimated Future Amortization Expense of Finite-Lived Intangibles
Cash received in Veritable Transaction		$ 287.4
Affiliate Transaction gain	$ 0	$ 133.1	$ 0	$ 133.1
Third Party
Estimated Future Amortization Expense of Finite-Lived Intangibles
Subsidiary, ownership percentage, sold		1		1
Acquired Client Relationships
Intangible Assets
Amortization and impairment expenses of intangible assets	7.3	$ 12.5	21.8	$ 37.5
Estimated Future Amortization Expense of Finite-Lived Intangibles
Finite-lived intangible, future amortization expense, remainder of fiscal year	7		7
Finite-lived intangible, future amortization expense in year one	25		25
Finite-lived intangible, future amortization expense in year two	25		25
Finite-lived intangible, future amortization expense in year three	25		25
Finite-lived intangible, future amortization expense in year four	25		25
Finite-lived intangible, future amortization expense in year five	$ 15		$ 15

Equity Method Investments in _3

Equity Method Investments in Affiliates - Schedule of Equity Method Investments in Affiliates (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Schedule of Equity Method Investments [Line Items]
Goodwill	$ 2,532	$ 2,523.6
Equity method investments in Affiliates (net)	2,148.4	2,288.5
Equity Method Investee
Schedule of Equity Method Investments [Line Items]
Goodwill	1,348.1	1,323.3
Definite-lived acquired client relationships (net)	568.1	652.5
Indefinite-lived acquired client relationships (net)	122.4	122.6
Undistributed earnings and tangible capital	109.8	190.1
Equity method investments in Affiliates (net)	$ 2,148.4	$ 2,288.5

Equity Method Investments in _4

Equity Method Investments in Affiliates - Change in Equity Method Investments (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Change in Equity Method Investments in Affiliates [Roll Forward]
Balance, as of December 31, 2023	$ 2,288.5
Distributions of earnings	(357.3)	$ (421.7)
Balance, as of September 30, 2024	2,148.4
Equity Method Investee
Change in Equity Method Investments in Affiliates [Roll Forward]
Balance, as of December 31, 2023	2,288.5
Investments in Affiliates	12.3
Earnings	292.6
Intangible amortization and impairments	(104.3)
Distributions of earnings	(357.3)
Foreign currency translation	16.6
Balance, as of September 30, 2024	$ 2,148.4

Equity Method Investments in _5

Equity Method Investments in Affiliates - Additional Information (Details) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2024 USD ($) yr affiliate	Jun. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) yr affiliate	Sep. 30, 2023 USD ($)	Dec. 31, 2023 affiliate
Estimated Future Amortization Expense of Finite-Lived Intangibles
Number of affiliates \| affiliate	22			22		22
Acquired Client Relationships
Schedule of Equity Method Investments [Line Items]
Amortization of intangible assets	$ 7.3		$ 12.5	$ 21.8	$ 37.5
Estimated Future Amortization Expense of Finite-Lived Intangibles
Finite-lived intangible, future amortization expense, remainder of fiscal year	7			7
Finite-lived intangible, future amortization expense in year one	25			25
Finite-lived intangible, future amortization expense in year two	25			25
Finite-lived intangible, future amortization expense in year three	25			25
Finite-lived intangible, future amortization expense in year four	25			25
Finite-lived intangible, future amortization expense in year five	$ 15			$ 15
Equity Method Investee
Estimated Future Amortization Expense of Finite-Lived Intangibles
Impairment expense		$ 39.9
Equity Method Investee \| Measurement Input, Growth Rate Period
Estimated Future Amortization Expense of Finite-Lived Intangibles
Equity method investment, measurement input \| yr	10			10
Equity Method Investee \| Measurement Input, Growth Rate
Estimated Future Amortization Expense of Finite-Lived Intangibles
Equity method investment, measurement input	(0.025)			(0.025)
Equity Method Investee \| Measurement Input, Long-Term Growth Rate
Estimated Future Amortization Expense of Finite-Lived Intangibles
Equity method investment, measurement input	0.03			0.03
Equity Method Investee \| Measurement Input, Discount Rate, Asset Based Fees
Estimated Future Amortization Expense of Finite-Lived Intangibles
Equity method investment, measurement input	0.12			0.12
Equity Method Investee \| Measurement Input, Discount Rate, Performance Based Fees
Estimated Future Amortization Expense of Finite-Lived Intangibles
Equity method investment, measurement input	0.20			0.20
Equity Method Investee \| Measurement Input, Market Participant Tax Rates
Estimated Future Amortization Expense of Finite-Lived Intangibles
Equity method investment, measurement input	0.21			0.21
Equity Method Investee \| Acquired Client Relationships
Schedule of Equity Method Investments [Line Items]
Amortization of intangible assets	$ 22.7		$ 21.2	$ 64.4	$ 63
Estimated Future Amortization Expense of Finite-Lived Intangibles
Finite-lived intangible, future amortization expense, remainder of fiscal year	23			23
Finite-lived intangible, future amortization expense in year one	75			75
Finite-lived intangible, future amortization expense in year two	70			70
Finite-lived intangible, future amortization expense in year three	70			70
Finite-lived intangible, future amortization expense in year four	60			60
Finite-lived intangible, future amortization expense in year five	$ 45			$ 45

Related Party Transactions (Det

Related Party Transactions (Details) $ in Millions	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Related Party Transactions
Other liabilities	$ 464.5	$ 466.3
Common stock, voting rights, percent	0.05
Related Party
Related Party Transactions
Other liabilities	$ 58.9	53.9
Related Party \| Private Equity Investment Partnerships of Affiliate
Related Party Transactions
Other liabilities	$ 15	$ 18.5

Share-Based Compensation - Shar

Share-Based Compensation - Share-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Payment Arrangement [Abstract]
Share-based compensation expense	$ 10.2	$ 14.5	$ 42.1	$ 43.9
Tax benefit	$ 1.2	$ 1.9	$ 5.2	$ 5.5

Share-Based Compensation - Narr

Share-Based Compensation - Narrative (Details) - USD ($)	9 Months Ended
Share-Based Compensation - Narrative (Details) - USD ($)	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Share-based Compensation
Unrecognized share-based compensation expense	$ 48,700,000		$ 54,400,000
Unrecognized share-based compensation expense, period for recognition	2 years
Stock options granted, fair value	$ 0	$ 0
Restricted Stock Units
Share-based Compensation
Restricted stocks granted, fair value	$ 31,300,000	$ 49,200,000
Restricted Stock Units \| Minimum
Share-based Compensation
Stock options, vesting period	3 years
Restricted Stock Units \| Maximum
Share-based Compensation
Stock options, vesting period	4 years
Stock Options
Share-based Compensation
Stock options, expiration period	7 years
Stock Options \| Minimum
Share-based Compensation
Stock options, vesting period	3 years
Stock Options \| Maximum
Share-based Compensation
Stock options, vesting period	5 years

Share-Based Compensation - Rest

Share-Based Compensation - Restricted Stock Units Transactions (Details) - Restricted Stock Units shares in Millions	9 Months Ended
	Sep. 30, 2024 $ / shares shares
Restricted Stock Units
Unvested units - beginning balance (in shares) \| shares	0.9
Units granted (in shares) \| shares	0.2
Units vested (in shares) \| shares	(0.3)
Units forfeited (in shares) \| shares	0
Performance condition changes (in shares) \| shares	0
Unvested units - ending balance (in shares) \| shares	0.8
Weighted Average Grant Date Value
Unvested units - beginning balance (in dollars per share) \| $ / shares	$ 138.51
Units granted (in dollars per share) \| $ / shares	159.32
Units vested (in dollars per share) \| $ / shares	129.72
Units forfeited (in dollars per share) \| $ / shares	149
Performance condition changes (in dollars per share) \| $ / shares	154.72
Unvested units - ending balance (in dollars per share) \| $ / shares	$ 147.40

Share-Based Compensation - Sche

Share-Based Compensation - Schedule of the Transactions of the Company's Stock Options (Details) shares in Millions	9 Months Ended
	Sep. 30, 2024 $ / shares shares
Stock Options
Unexercised options outstanding - beginning balance (in shares) \| shares	3.2
Options granted (in shares) \| shares	0
Options exercised (in shares) \| shares	(1.3)
Options forfeited (in shares) \| shares	0
Options expired (in shares) \| shares	0
Performance condition changes (in shares) \| shares	0
Unexercised options outstanding - ending balance (in shares) \| shares	1.9
Stock Options, Exercisable at the end of the period (in shares) \| shares	1.5
Weighted Average Exercise Price
Unexercised options outstanding - beginning balance (in dollars per share) \| $ / shares	$ 76.74
Options granted (in dollars per share) \| $ / shares	0
Options exercised (in dollars per share) \| $ / shares	74.82
Options forfeited (in dollars per share) \| $ / shares	185.98
Options expired (in dollars per share) \| $ / shares	152.36
Performance condition changes (in dollars per share) \| $ / shares	129.17
Unexercised options outstanding - ending balance (in dollars per share) \| $ / shares	78.02
Weighted Average Exercise Price, Exercisable at the end of the period (in dollars per share) \| $ / shares	$ 75.89
Weighted Average Remaining Contractual Life (Years)
Unexercised options outstanding at the end of the period	2 years 1 month 6 days
Exercisable at the end of the period	1 year 10 months 24 days

Redeemable Non-Controlling In_3

Redeemable Non-Controlling Interests (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Redeemable Noncontrolling Interest [Roll Forward]
Balance, beginning balance			$ 393.4
Increase attributable to consolidated Affiliate sponsored investment products			1.5
Transfers to Other liabilities			(42.2)
Transfers from Non-controlling interests			1.7
Changes in redemption value	$ 12	$ (50.3)	42.7	$ 46.9
Balance, ending balance	397.1		$ 397.1
Minimum
Noncontrolling Interest [Line Items]
Term of conditional right to put interest			5 years
Maximum
Noncontrolling Interest [Line Items]
Term of conditional right to put interest			15 years
Variable Interest Entity, Primary Beneficiary
Redeemable Noncontrolling Interest [Roll Forward]
Balance, beginning balance			$ 11.8
Balance, ending balance	$ 13.3		$ 13.3

Affiliate Equity - Additional I

Affiliate Equity - Additional Information (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Affiliate Equity [Line Items]
Distributions paid to affiliate partners	$ 206.5	$ 216.4
Payments to acquire interest in affiliates	60.4	41.7
Issuance of interest in affiliates	6.3	$ 13.4
Other assets	287.8		$ 243.9
Other liabilities	464.5		466.3
Related Party
Affiliate Equity [Line Items]
Other assets	4.5		5.9
Other liabilities	$ 58.9		$ 53.9

Affiliate Equity - Summary of A

Affiliate Equity - Summary of Affiliate Recognized and Unrecognized Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Affiliate Equity [Line Items]
Affiliate equity compensation expense	$ 12.1	$ 11.5	$ 46.5	$ 39.5
Non- controlling Interests
Affiliate Equity [Line Items]
Non-controlling interests	9.7	11.5	$ 30.9	33.4
Unrecognized Affiliate Equity Expense [Abstract]
Remaining Life			6 years		6 years
Non-controlling Interests	217.6		$ 217.6		$ 235.7
Affiliated Entity
Affiliate Equity [Line Items]
Controlling interest	2.4	$ 0	15.6	$ 6.1
Unrecognized Affiliate Equity Expense [Abstract]
Controlling Interest	$ 39		$ 39		$ 30.6
Remaining Life			4 years		5 years

Affiliate Equity - Changes in t

Affiliate Equity - Changes in the Company's Interest in its Affiliates on the Controlling Interest's Equity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Affiliate Equity [Abstract]
Net income (controlling interest)	$ 123.6	$ 217	$ 349.5	$ 476.8
Decrease in controlling interest paid-in capital from Affiliate equity issuances	0	(4.5)	(2.6)	(13.1)
Increase (decrease) in controlling interest paid-in capital from Affiliate equity purchases	(0.5)	1.9	(22.9)	(36.1)
Net income (controlling interest) including the net impact of Affiliate equity transactions	$ 123.1	$ 214.4	$ 324	$ 427.6

Income Taxes - Schedule of Cons

Income Taxes - Schedule of Consolidated Provision for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Tax Provision
Income tax expense	$ 31.3	$ 77.7	$ 130	$ 155.4
Deferred income tax (benefit) expense related to intangibles	16.4	(13.5)	50.6	16.4
Non- controlling Interests
Income Tax Provision
Income tax expense	1.8	1.8	6.3	5.5
Controlling Interest
Income Tax Provision
Income tax expense	29.5	75.9	123.7	149.9
Income before income taxes (controlling interest)	$ 153.1	$ 292.9	$ 473.2	$ 626.7
Effective tax rate (controlling interests)	19.30%	25.90%	26.10%	23.90%

Earnings Per Share - Schedule o

Earnings Per Share - Schedule of Basic and Diluted Earnings (Loss) Per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Numerator
Net income (controlling interest)	$ 123.6	$ 217	$ 349.5	$ 476.8
Income from hypothetical settlement of Redeemable non-controlling interests, net of taxes	5.2	17.1	1	39.4
Interest expense on junior convertible securities, net of taxes	3.4	3.4	10.1	10.1
Net income (controlling interest), as adjusted	$ 132.2	$ 237.5	$ 360.6	$ 526.3
Denominator
Average shares outstanding (basic) (in shares)	30.1	34.9	31.4	35.6
Effect of dilutive instruments:
Stock options and restricted stock units (in shares)	1.7	1.7	1.9	1.7
Hypothetical issuance of shares to settle Redeemable non-controlling interests (in shares)	1.5	5.1	0.2	3.9
Junior convertible securities (in shares)	1.7	1.7	1.7	1.7
Average shares outstanding (diluted) (in shares)	35	43.4	35.2	42.9

Earnings Per Share - Schedule_2

Earnings Per Share - Schedule of Shares Excluded from Calculation of Basic and Diluted Earnings (Loss) Per Share (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Stock options and restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0.2	0.2	0.2	0.3
Shares issuable to settle Redeemable non-controlling interests
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	2.3	0.1	3.6	0.7

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Details) - $ / shares shares in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024
Earnings Per Share [Abstract]
Number or shares repurchased during period (in shares)	0.6	3.6
Average price of shares repurchased during period (in dollars per share)	$ 163.23	$ 158.62

Comprehensive Income - Summary

Comprehensive Income - Summary of the Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss)
Pre-Tax	$ 39.6	$ (27.3)	$ 46.7	$ 28.3
Tax (Expense) Benefit	0.6	(3)	(2.3)	(6.8)
Other comprehensive income (loss), net of tax	40.2	(30.3)	44.4	21.5
Foreign currency translation gain (loss)
Accumulated Other Comprehensive Income (Loss)
Pre-Tax	38.6	(27.6)	44.8	27.5
Tax (Expense) Benefit	0.6	(3)	(2.2)	(6.9)
Other comprehensive income (loss), net of tax	39.2	(30.6)	42.6	20.6
Change in net realized and unrealized gain (loss) on derivative financial instruments
Accumulated Other Comprehensive Income (Loss)
Pre-Tax	1	(0.3)	1.4	0.5
Tax (Expense) Benefit	0	0	0	0
Other comprehensive income (loss), net of tax	1	(0.3)	1.4	0.5
Change in net unrealized gain (loss) on available-for-sale debt securities
Accumulated Other Comprehensive Income (Loss)
Pre-Tax	0	0.6	0.5	0.3
Tax (Expense) Benefit	0	0	(0.1)	0.1
Other comprehensive income (loss), net of tax	$ 0	$ 0.6	$ 0.4	$ 0.4

Comprehensive Income - Componen

Comprehensive Income - Components of AOCL (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Components of Accumulated other comprehensive income, net of taxes
Beginning balance	$ 4,262.7	$ 4,368.4	$ 4,570.1	$ 4,175.6
Other comprehensive income before reclassifications			43.8
Amounts reclassified			0.6
Other comprehensive income (loss), net of tax	40.2	(30.3)	44.4	21.5
Ending balance	4,274	4,464.2	4,274	4,464.2
Total
Components of Accumulated other comprehensive income, net of taxes
Beginning balance			(255.9)
Ending balance	(211.5)		(211.5)
Foreign Currency Translation Adjustment
Components of Accumulated other comprehensive income, net of taxes
Beginning balance			(255.3)
Other comprehensive income before reclassifications			42.6
Amounts reclassified			0
Other comprehensive income (loss), net of tax	39.2	(30.6)	42.6	20.6
Ending balance	(212.7)		(212.7)
Realized and Unrealized Gains (Losses) on Derivative Financial Instruments
Components of Accumulated other comprehensive income, net of taxes
Beginning balance			(0.1)
Other comprehensive income before reclassifications			0.8
Amounts reclassified			0.6
Other comprehensive income (loss), net of tax	1	(0.3)	1.4	0.5
Ending balance	1.3		1.3
Unrealized Gains (Losses) on Investment Available-for-Sale Debt Securities
Components of Accumulated other comprehensive income, net of taxes
Beginning balance			(0.5)
Other comprehensive income before reclassifications			0.4
Amounts reclassified			0
Other comprehensive income (loss), net of tax	0	$ 0.6	0.4	$ 0.4
Ending balance	$ (0.1)		$ (0.1)