Affiliated Managers (MGR) 10-Q 9 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 07, 2019
Document and Entity Information
Entity Registrant Name	AFFILIATED MANAGERS GROUP, INC.
Entity Central Index Key	0001004434
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		51,199,344
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Consolidated revenue	$ 543.1	$ 612.4
Consolidated expenses:
Compensation and related expenses	228.2	266.7
Selling, general and administrative	95.6	106.4
Intangible amortization and impairments	29.6	23.2
Interest expense	18.2	21.6
Depreciation and other amortization	5.2	5.5
Other expenses (net)	11	12
Total consolidated expenses	387.8	435.4
Equity method income (loss) (net)	(358.1)	96.3
Investment and other income	8	14.2
Income (loss) before income taxes	(194.8)	287.5
Income tax expense (benefit)	(61.8)	63.5
Net income (loss)	(133)	224
Net income (non-controlling interests)	(67.8)	(71)
Net income (loss) (controlling interest)	$ (200.8)	$ 153
Average shares outstanding (basic) (in shares)	51.9	54.6
Average shares outstanding (diluted) (in shares)	51.9	57
Earnings (loss) per share (basic) (in dollars per share)	$ (3.87)	$ 2.80
Earnings (loss) per share (diluted) (in dollars per share)	$ (3.87)	$ 2.77

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (133)	$ 224
Other comprehensive income, net of tax:
Foreign currency translation gain	7.5	29.1
Change in net realized and unrealized gain on derivative financial instruments	1.2	0.3
Other comprehensive income, net of tax	8.7	29.4
Comprehensive income (loss)	(124.3)	253.4
Comprehensive income (non-controlling interests)	(74.4)	(79.5)
Comprehensive income (loss) (controlling interest)	$ (198.7)	$ 173.9

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents		$ 305.2	$ 565.5
Receivables		535.5	400.6
Investments in marketable securities		36.4	119.3
Goodwill		2,642.4	2,633.4
Acquired client relationships (net)		1,289.5	1,309.9
Equity method investments in Affiliates (net)		2,318.5	2,791
Fixed assets (net)		102.3	104.3
Other investments		207.5	201.1
Other assets		239.7	94
Total assets		7,677	8,219.1
Liabilities and Equity
Payables and accrued liabilities		576.5	746.6
Debt		1,780.7	1,829.6
Deferred income tax liability (net)		418.5	511.6
Other liabilities		386.2	162.7
Total liabilities		3,161.9	3,250.5
Commitments and contingencies (Note 8)
Redeemable non-controlling interests	[1]	754.8	833.7
Equity:
Common stock ($0.01 par value, 153.0 shares authorized; 58.5 shares outstanding in 2018 and 2019)		0.6	0.6
Additional paid-in capital		804.4	835.6
Accumulated other comprehensive loss		(106.9)	(109)
Retained earnings		3,652.6	3,876.8
Total stockholders' equity before treasury stock		4,350.7	4,604
Less: Treasury stock, at cost (6.5 shares in 2018 and 7.1 shares in 2019)		(1,210.3)	(1,146.6)
Total stockholders' equity		3,140.4	3,457.4
Non-controlling interests		619.9	677.5
Total equity		3,760.3	4,134.9
Total liabilities and equity		$ 7,677	$ 8,219.1
[1]	As of December 31, 2018 and March 31, 2019, Redeemable non-controlling interests includes consolidated Affiliate sponsored investment products primarily attributable to third-party investors of $91.0 million and $6.5 million, respectively.

CONSOLIDATED BALANCE SHEETS - P

CONSOLIDATED BALANCE SHEETS - Parenthetical - $ / shares shares in Millions	Mar. 31, 2019	Dec. 31, 2018
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 outstanding (in shares)	58.5	58.5
Treasury stock, at cost (in shares)	7.1	6.5

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Treasury Stock at Cost	Non- controlling Interests
Beginning Balance (in shares) at Dec. 31, 2017		58.5
Beginning Balance at Dec. 31, 2017	$ 4,578.5	$ 0.6	$ 808.6	$ (21.8)	$ 3,698.5	$ (663.7)	$ 756.3
Increase (Decrease) in Stockholders' Equity
Net income (loss)	224				153		71
Other comprehensive income	29.4			20.9			8.5
Share-based compensation	10.7		10.7
Common stock issued under share-based incentive plans	(9.5)		(2.2)			(7.3)
Share repurchases	(150.8)					(150.8)
Dividends ($0.30 per share and $0.32 per share)	(16.6)				(16.6)
Affiliate equity activity:
Affiliate equity compensation	19.4		2.6				16.8
Issuances	7		(1.4)				8.4
Repurchases	14.4		14.4
Changes in redemption value of Redeemable non-controlling interests	(168.5)		(168.5)
Transfers to Redeemable non-controlling interests	(4.9)						(4.9)
Capital contributions by Affiliate equity holders	1.9						1.9
Distributions to non-controlling interests	(112.4)						(112.4)
Ending Balance (in shares) at Mar. 31, 2018		58.5
Ending Balance at Mar. 31, 2018	$ 4,422.6	$ 0.6	664.2	(0.9)	3,834.9	(821.8)	745.6
Beginning Balance (in shares) at Dec. 31, 2018	58.5	58.5
Beginning Balance at Dec. 31, 2018	$ 4,134.9	$ 0.6	835.6	(109)	3,876.8	(1,146.6)	677.5
Increase (Decrease) in Stockholders' Equity
Net income (loss)	(133)				(200.8)		67.8
Other comprehensive income	8.7			2.1			6.6
Share-based compensation	8.8		8.8
Common stock issued under share-based incentive plans	(6.1)		(33)			26.9
Share repurchases	(90.6)					(90.6)
Dividends ($0.30 per share and $0.32 per share)	(16.8)				(16.8)
Affiliate equity activity:
Affiliate equity compensation	10.7		2.2				8.5
Issuances	10.1		(0.9)				11
Repurchases	4.6		4.6
Changes in redemption value of Redeemable non-controlling interests	(12.9)		(12.9)
Transfers to Redeemable non-controlling interests	(47.3)						(47.3)
Capital contributions by Affiliate equity holders	0.4						0.4
Distributions to non-controlling interests	$ (104.6)						(104.6)
Ending Balance (in shares) at Mar. 31, 2019	58.5	58.5
Ending Balance at Mar. 31, 2019	$ 3,760.3	$ 0.6	$ 804.4	$ (106.9)	$ 3,652.6	$ (1,210.3)	$ 619.9

CONSOLIDATED STATEMENTS OF CH_2

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - Parenthetical - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Dividends per share (in dollars per share)	$ 0.32	$ 0.30

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flow from (used in) operating activities:
Net income (loss)	$ (133)	$ 224
Adjustments to reconcile Net income (loss) to cash flow from (used in) operating activities:
Intangible amortization and impairments	29.6	23.2
Depreciation and other amortization	5.2	5.5
Deferred income tax expense (benefit)	(86)	13.4
Equity method (income) loss (net)	358.1	(96.3)
Distributions of earnings received from equity method investments	96.5	225.7
Share-based compensation and Affiliate equity expense	19.5	30.1
Other non-cash items	(4.4)	1.2
Changes in assets and liabilities:
Purchases of securities by consolidated Affiliate sponsored investment products	0	(9.9)
Sales of securities by consolidated Affiliate sponsored investment products	1.5	12.5
Increase in receivables	(131.3)	(92.4)
Increase in other assets	(0.7)	(4)
Decrease in payables, accrued liabilities and other liabilities	(172.9)	(128)
Cash flow from (used in) operating activities	(17.9)	205
Cash flow from (used in) investing activities:
Investments in Affiliates	(34.1)	0
Divestments of Affiliates	28.8	0
Purchase of fixed assets	(3)	(5.5)
Purchase of investment securities	(8.7)	(5)
Sale of investment securities	16.9	6.6
Cash flow used in investing activities	(0.1)	(3.9)
Cash flow from (used in) financing activities:
Borrowings of debt	336.3	440
Repayments of debt	(385)	(435)
Repurchases of common stock (net)	(71)	(170.1)
Dividends paid on common stock	(17)	(16.4)
Distributions to non-controlling interests	(104.6)	(112.4)
Affiliate equity issuances and repurchases (net)	(6)	(8.3)
Other financing items	3.6	(10.9)
Cash flow used in financing activities	(243.7)	(313.1)
Effect of foreign currency exchange rate changes on cash and cash equivalents	4	6.7
Net decrease in cash and cash equivalents	(257.7)	(105.3)
Cash and cash equivalents at beginning of period	565.5	439.5
Effect of deconsolidation of Affiliate sponsored investment products	(2.6)	0
Cash and cash equivalents at end of period	$ 305.2	$ 334.2

Basis of Presentation and Use o

Basis of Presentation and Use of Estimates	3 Months Ended
	Mar. 31, 2019
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. (the “Company”) have been prepared in accordance with accounting principles generally accepted in the United States of America (“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. Certain reclassifications have been made to the prior period’s financial statements to conform to the current period’s presentation. 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, 2018 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 indicated.

Accounting Standards and Polici

Accounting Standards and Policies	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Accounting Standards and Policies	Accounting Standards and Policies Recently Adopted Accounting Standards Effective January 1, 2019, the Company adopted the following new Accounting Standard Updates (“ASUs”): • ASU 2016-02, Leases (and related ASUs); • ASU 2018-02, Income Statement - Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income; and • ASU 2014-09, Revenue from Contracts with Customers (and related ASUs, effective for the Company’s equity method Affiliates) The adoption of ASU 2016-02 was the only ASU that had a significant impact on the Company’s Consolidated Financial Statements. The Company adopted ASU 2016-02 using a modified retrospective method and, as a result, recorded a lease liability of $190.8 million and after certain reclassifications, primarily related to accrued lease payments and unamortized lease incentives, a right-of-use asset of $163.6 million as of January 1, 2019. Additionally, the Company elected the transition practical expedients provided by ASU 2016-02, which allowed the Company to carryforward its historical lease classification. Having adopted ASU 2016-02, the Company updated its leases accounting policy as described below. For a complete list of significant accounting policies, see the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018 . Leases Leases are classified as either operating leases or finance leases. The Company and its Affiliates currently lease office space and equipment primarily under operating lease arrangements. As these leases expire, it is expected that, in the normal course of business, they will be renewed or replaced. Whether a lease is classified as an operating lease or a finance lease, the Company and its Affiliates must record a right-of-use asset and a lease liability for all leases at the commencement date of the lease, other than for leases with an initial term of 12 months or less. As permitted under ASU 2016-02, the Company and its Affiliates elect not to record short-term leases with an initial lease term less than 12 months on the Company’s Consolidated Balance Sheets. Right-of-use assets and lease liabilities are reported in Other assets and Other liabilities, respectively, on the Consolidated Balance Sheets. A lease liability is initially and subsequently reported at the present value of the outstanding lease payments determined by discounting those lease payments over the remaining lease term using the incremental borrowing rate of the legal entity entering into the lease as of the commencement date. A right-of-use asset is initially reported at the present value of the corresponding lease liability plus any prepaid lease payments and initial direct costs of entering into the lease, and reduced by any lease incentives. Subsequently, a right-of-use asset is reported at the present value of the lease liability adjusted for any prepaid or accrued lease payments, remaining balances of any lease incentives received, unamortized initial direct costs of entering into the lease and any impairments of the right-of-use asset. The Company and its Affiliates test for possible impairments of right-of-use assets annually or more frequently whenever events or changes in circumstances indicate that the carrying value of a right-of-use asset may exceed its fair value. If the carrying value of the right-of-use asset exceeds its fair value, then the carrying value of the right-of-use asset is reduced to its fair value and the expense is recorded in Other expenses (net) on the Consolidated Statements of Income. Subsequent to an impairment, the carrying value of the right-of-use asset is amortized on a straight-line basis over the remaining lease term. Lease liabilities and right-of-use assets based on variable lease payments that depend on an index or rate are initially measured using the index or rate at the commencement date with any subsequent changes in variable lease payments reported in Other expenses (net) as incurred. Most lease agreements for office space that are classified as operating leases contain renewal options, rent escalation clauses or other lease incentives provided by the lessor. Lease expense is accrued to recognize lease escalation provisions and renewal options that are reasonably certain to be exercised, as well as lease incentives provided by the lessor, on a straight-line basis over the lease term and is reported in Other expenses (net). If a right-of-use asset is impaired, the lease expense is subsequently reported in Other expenses (net) as the straight-line amortization of the right-of-use asset and the accretion of the lease liability, thereby transitioning to a front-loaded expense recognition profile for the associated lease. The Company and its Affiliates combine lease and non-lease components for their office space leases and separate non-lease components for their equipment leases in calculating their lease liabilities. Sublease income is reported in Investment and other income on the Consolidated Statements of Income.

Investments in Marketable Secur

Investments in Marketable Securities	3 Months Ended
	Mar. 31, 2019
Marketable Securities [Abstract]
Investments in Marketable Securities	Investments in Marketable Securities The following is a summary of the cost, gross unrealized gains, and losses and fair value of Investments in marketable securities: December 31, March 31, Cost $ 126.8 $ 35.0 Unrealized gains 1.1 1.6 Unrealized losses (8.6 ) (0.2 ) Fair value $ 119.3 $ 36.4 For the three months ended March 31, 2018 and 2019 , the Company received proceeds of $13.8 million and $15.1 million , respectively, from the sale of investments in marketable securities, and recorded net gains of $2.8 million and $0.5 million , respectively. For the three months ended March 31, 2019 , the Company deconsolidated an Affiliate sponsored investment product with a fair value of $84.3 million .

Investments in Affiliates and A

Investments in Affiliates and Affiliate Sponsored Investment Products	3 Months Ended
	Mar. 31, 2019
Variable Interest Entities
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 entity under the equity method. Other investments in which the Company does not have rights to exercise significant influence are recorded at fair value, with changes in fair value reflected within Investment and other income on the Consolidated Statements of 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 Affiliates’ 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 equity ownership is included in Net income (non-controlling interests) in the Consolidated Statements of Income. Undistributed earnings attributable to Affiliate managements’ equity ownership, along with their share of any tangible or intangible net assets, are presented within 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 on the Consolidated Balance Sheets. The Company periodically issues, sells and repurchases 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 within 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 (loss) (net) in the Consolidated Statements of Income and the carrying value of the Affiliate is reported in Equity method investments in Affiliates (net) in the Consolidated Balance Sheets. Any deferred taxes recorded upon acquisition of an equity method Affiliate are presented on a gross basis within Equity method investments in Affiliates (net) and Deferred income tax liability (net) in the Consolidated Balance Sheets. The Company’s share of income taxes incurred directly by Affiliates accounted for under the equity method is recorded within Income tax expense (benefit) in the Consolidated Statements of Income. The Company periodically evaluates its equity method Affiliates for impairment. In such impairment evaluations, the Company assesses whether or not the fair value of the investment has declined below its carrying value for a period considered to be other-than-temporary. If the Company determines that a decline in fair value below the carrying value of the investment is other-than-temporary, then the carrying value of the investment is reduced to its fair value and the expense is recorded in Equity method income (loss) (net). The unconsolidated assets, net of liabilities and non-controlling interests of equity method Affiliates considered VIEs, and the Company’s carrying value and maximum exposure to loss, were as follows: December 31, 2018 March 31, 2019 Unconsolidated Carrying Value and Unconsolidated Carrying Value and Affiliates accounted for under the equity method $ 1,102.9 $ 2,277.8 $ 1,167.6 $ 1,822.9 As of December 31, 2018 and March 31, 2019 , the carrying value and maximum exposure to loss for all of the Company’s equity method Affiliates was $2,791.0 million and $2,318.5 million , respectively, including equity method Affiliates considered VREs of $513.2 million and $495.6 million , respectively. Affiliate Sponsored Investment Products The Company’s Affiliates sponsor various investment products where they also act 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 does not generally consolidate these products unless the Company’s or its consolidated Affiliate’s interest in the product is considered substantial. When the Company’s or its consolidated Affiliates’ interests are considered substantial and 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 in the Consolidated Balance Sheets, with corresponding changes in the investments’ fair values reflected in Investment and other income. Purchases and sales of securities are presented within purchases and sales by consolidated Affiliate sponsored investment products in the Consolidated Statements of Cash Flows 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 Affiliate’s interest 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, 2018 March 31, 2019 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 $ 2,216.5 $ 1.1 $ 2,208.5 $ 0.6

Debt

Debt	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Debt	Debt The Company’s Debt consisted of the following: December 31, March 31, Senior bank debt $ 779.7 $ 459.7 Senior notes 742.5 742.8 Junior convertible securities 307.4 308.2 Junior subordinated notes — 270.0 Debt $ 1,829.6 $ 1,780.7 Long-term debt is carried at amortized cost. Unamortized discounts and debt issuance costs related to long-term debt are presented in the Consolidated Balance Sheets as an adjustment to the carrying value of the associated long-term debt. Senior Bank Debt On January 18, 2019, the Company amended and restated its existing credit facilities to provide for a $1.25 billion senior unsecured multicurrency revolving credit facility (the “revolver”) and a $450.0 million senior unsecured term loan facility (the “term loan” and, together with the revolver, the “credit facilities”). The revolver matures on January 18, 2024, and the term loan matures on January 18, 2023. Subject to certain conditions, the Company may increase the commitments under the revolver by up to an additional $500.0 million and may borrow up to an additional $75.0 million under the term loan. The Company pays interest on any outstanding obligations under the credit facilities at specified rates, based either on an applicable LIBOR or prime rate, plus a marginal rate determined based on its credit rating. For the three months ended March 31, 2019, the interest rate for substantially all of the Company’s borrowings under the credit facilities was LIBOR plus 1.10% for the revolver and LIBOR plus 0.875% for the term loan. Junior Subordinated Notes On March 27, 2019, the Company issued $280.0 million of junior subordinated notes with a maturity date of March 30, 2059. The junior subordinated notes bear interest at a fixed rate of 5.875% per annum, payable quarterly in cash, commencing on June 30, 2019, subject to the Company’s right to defer interest payments in accordance with the terms of the junior subordinated notes. The 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. On or after March 30, 2024, at the Company’s option, the junior subordinated notes may be redeemed in whole or in part, at 100% of the principal amount, plus any accrued and unpaid interest. Prior to March 30, 2024, at the Company’s option, the junior subordinated notes may 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 junior subordinated notes. On April 8, 2019, the Company issued an additional $20.0 million of junior subordinated notes pursuant to the underwriters’ exercise of an overallotment option, which increased the total amount issued to $300.0 million .

Equity Distribution Program

Equity Distribution Program	3 Months Ended
	Mar. 31, 2019
Forward Equity Sale Agreements
Equity Distribution Program	Equity Distribution Program On March 27, 2019, the Company entered into equity distribution and forward equity agreements with several major securities firms under which it may, from time to time, issue and sell shares of its common stock (immediately or on a forward basis) having an aggregate sales price of up to $500.0 million (the “equity distribution program”). This equity distribution program superseded and replaced the Company’s prior equity distribution program. As of March 31, 2019 , no sales had occurred under the new or prior equity distribution program.

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments The Company and its Affiliates may use derivative financial instruments to offset exposure to changes in interest rates, foreign currency exchange rates and markets. The Company has two separate pound sterling-denominated forward foreign currency contracts (the “forward contracts”) with a large financial institution (the “counterparty”). Concurrent to entering into each of the forward contracts, the Company also entered into two separate collar contracts (the “collar contracts”) with the same counterparty for the same notional amounts and expiration dates as the forward contracts. Under one of the forward contracts, the Company will deliver £285.8 million for $400.0 million in 2024 and under the other forward contract, the Company will deliver £325.3 million for $450.0 million in 2021. Under one of the collar contracts, the Company sold a put option with a lower strike price of 1.288 U.S. dollars per one pound sterling and purchased a call option with an upper strike price of 1.535 U.S. dollars per one pound sterling. Under the other collar contract, the Company sold a put option with a lower strike price of 1.318 U.S. dollars per one pound sterling and purchased a call option with an upper strike price of 1.448 U.S. dollars per one pound sterling. The combination of the forward contracts and the collar contracts were designated as net investment hedges against fluctuations in foreign currency exchange rates on certain of the Company’s investments in Affiliates with the pound sterling as their functional currency. Changes in the fair values of the effective net investment hedges are reported in Foreign currency translation gain (loss) in the Consolidated Statements of Comprehensive Income. The Company assesses hedge effectiveness on a quarterly basis. The Company’s Affiliates use forward foreign currency contracts to hedge the risk of foreign exchange rate movements, which were not significant for the three months ended March 31, 2018 and 2019 . Derivative financial instruments are presented in Other assets when in an unrealized gain position and in Other liabilities when in an unrealized loss position. When a right to offset exists between derivative financial instruments they are presented net in the Consolidated Balance Sheets. The following table summarizes the Company’s and its Affiliates’ derivative financial instruments measured at fair value on a recurring basis: December 31, 2018 March 31, 2019 Assets Liabilities Assets Liabilities Forward contracts $ 32.0 $ (1.4 ) $ 17.2 $ (0.0 ) Put options — (60.3 ) — (42.4 ) Call options 34.1 — 26.6 — Total $ 66.1 $ (61.7 ) $ 43.8 $ (42.4 ) The following table summarizes the effect of the derivative financial instruments on the Consolidated Statements of Comprehensive Income and the Consolidated Statements of Income. For the three months ended March 31, 2018 , the Company and its Affiliates did not have any significant derivative financial instruments. For the Three Months Ended March 31, 2019 Gain (Loss) Recognized in Other Comprehensive Income Gain Recognized in Earnings from Excluded Components (1) Forward contracts $ (16.8 ) $ 3.5 Put options 17.9 — Call options (7.5 ) — Total $ (6.4 ) $ 3.5 (1) The excluded components of the forward contracts are recognized in earnings on a straight-line basis over the respective period of the contracts as a reduction to Interest expense on the Consolidated Statements of Income. As of March 31, 2019 , the Company and its Affiliates did not have any significant gains (losses) reclassified from Accumulated other comprehensive loss into earnings. The terms of the Company’s forward contracts and collar contracts provide net settlement rights and require the Company and the counterparty to post cash collateral in certain circumstances throughout the duration of the contracts. As of March 31, 2019 , the Company did no t hold any cash collateral from the counterpary and the counterparty held $14.9 million of cash collateral from the Company. The derivative contracts are governed by an International Swaps and Derivative Association (“ISDA”) Master Agreement with the counterparty, which provides for settlement netting and close-out netting between the Company and the counterparty, which are legally enforceable rights to setoff. The Company also actively monitors its counterparty credit risk related to derivative financial instruments. The Company’s derivative contracts include provisions to protect against counterparty rating downgrades, which in certain cases may result in the counterparty posting additional collateral to the Company or give the Company a termination right. The Company considers set-off rights and counterparty credit risk in the valuation of its positions and recognizes a credit valuation adjustment as appropriate. The Company’s forward contracts and collar contracts include contingent features that could require the Company or the counterparty to post additional collateral or give rise to termination rights, if certain specified rating downgrades were to occur. As of March 31, 2019 , there were no derivative arrangements with a contingent feature that were in a net liability position.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
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 March 31, 2019 , these unfunded commitments were $146.6 million and may be called in future periods. As of March 31, 2019 , the Company was contingently liable, upon the achievement by certain Affiliates of specified financial targets, to make payments of $152.5 million through 2020 related to the Company’s investments in these Affiliates. As of March 31, 2019 , the Company expected to make no significant payments for contingent payment arrangements. Affiliate equity interests provide holders with a conditional right to put their interests to the Company over time. See Note 16 for additional information. In addition, in connection with one of the Company’s investments in a non-U.S. alternative Affiliate accounted for under the equity method, the Company entered into an arrangement with a minority owner of the Affiliate that gives such owner the right to elect to sell a portion of its 19% ownership interest in the Affiliate to the Company annually. The purchase price of these conditional purchases will be at fair market value. During the three months ended March 31, 2019 , the Company was notified by the minority owner that it had elected to sell a 5% ownership interest in the Affiliate to the Company. The Company will pay $25.7 million for the interest, and the sale is expected to be completed in the second quarter of 2019. The Company will continue to account for the Affiliate under the equity method. The Company and certain of its consolidated Affiliates operate under regulatory authorities that require the maintenance of minimum financial or capital requirements. Management is not aware of any significant violations of such requirements.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The following tables summarize the Company’s financial assets and liabilities that are measured at fair value on a recurring basis: Fair Value Measurements December 31, 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 marketable securities $ 119.3 $ 119.3 $ — $ — Derivative financial instruments (1) 5.8 — 5.8 — Financial Liabilities (2) Contingent payment arrangements $ 1.9 $ — $ — $ 1.9 Affiliate equity repurchase obligations 36.2 — — 36.2 Derivative financial instruments 1.4 — 1.4 — Fair Value Measurements March 31, 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 marketable securities $ 36.4 $ 36.4 $ — $ — Derivative financial instruments (1) 1.4 — 1.4 — Financial Liabilities (2) Contingent payment arrangements $ 2.0 $ — $ — $ 2.0 Affiliate equity repurchase obligations 75.4 — — 75.4 Derivative financial instruments 0.0 — 0.0 — __________________________ (1) Amounts are presented within Other assets. (2) Amounts are presented within Other liabilities. Level 3 Financial Assets and Liabilities The following table presents the changes in level 3 liabilities: For the Three Months Ended March 31, 2018 2019 Contingent Payment Arrangements Affiliate Equity Repurchase Obligations Contingent Payment Arrangements Affiliate Equity Repurchase Obligations Balance, beginning of period $ 9.4 $ 49.2 $ 1.9 $ 36.2 Net realized and unrealized losses (1) 0.4 — 0.1 — Purchases and issuances (2) — 45.6 — 54.6 Settlements and reductions — (15.4 ) — (15.4 ) Balance, end of period $ 9.8 $ 79.4 $ 2.0 $ 75.4 Net change in unrealized losses relating to instruments still held at the reporting date $ 0.4 $ — $ 0.3 $ — ___________________________ (1) Accretion expense for these arrangements is recorded in Interest expense. (2) Includes transfers from Redeemable non-controlling interests. 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, 2018 March 31, 2019 Valuation Techniques Unobservable Input Fair Value Range Weighted Average Fair Value Range Weighted Average Contingent payment arrangements Discounted cash flow Growth rates $ 1.9 7% 7% $ 2.0 7% 7% Discount rates 15% 15% 15% 15% Affiliate equity repurchase obligations Discounted cash flow Growth rates 36.2 (4)% - 9% 3% 75.4 (4)% - 9% 5% Discount rates 14% - 16% 15% 13% - 17% 15% Contingent payment arrangements represent the present value of the expected future settlement amounts related to the Company’s investments in consolidated Affiliates. As of March 31, 2019 , there were no changes to growth rates or discount rates that had a significant impact to contingent payment arrangements. Affiliate equity repurchase obligations include agreements to repurchase Affiliate equity. As of March 31, 2019 , there were no changes to growth or discount rates that had a significant impact to Affiliate equity repurchase obligations recorded in prior periods. Investments Measured at NAV as a Practical Expedient The Company’s Affiliates sponsor investment products in which the Company and its Affiliates may make general partner and seed capital investments. The Company uses the net asset value (“NAV”) of these investments as a practical expedient for their fair values and reports these investments within Other investments. The following table summarizes the fair values of these investments and unfunded commitments: December 31, 2018 March 31, 2019 Category of Investment Fair Value Unfunded Commitments Fair Value Unfunded Commitments Private equity funds (1) $ 193.2 $ 131.0 $ 198.5 $ 146.6 Other funds (2) 7.9 — 9.0 — Other investments (3) $ 201.1 $ 131.0 $ 207.5 $ 146.6 ___________________________ (1) The Company uses NAV as a practical expedient one quarter in arrears (adjusted for current period calls and distributions) to determine the fair value. These funds primarily invest in a broad range of private equity funds, as well as making 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 long/short equity, credit and real estate. Investments are generally redeemable on a daily, monthly or quarterly basis. (3) Fair value attributable to the controlling interest was $123.2 million and $131.3 million as of December 31, 2018 and March 31, 2019 , respectively. Other Financial Assets and Liabilities Not Carried at Fair Value The Company has other financial assets and liabilities, which are not required to be carried at fair value, but the Company is required to disclose their fair values. The carrying amount of Cash and cash equivalents, Receivables, and Payables and accrued liabilities approximates fair value because of the short-term nature of these instruments. The carrying value of notes receivable, which is reported in Other assets, approximates fair value because interest rates and other terms are at market rates. The carrying value of the credit facilities approximates fair value because the credit facilities have variable interest based on selected short-term rates. The following table summarizes the Company’s other financial liabilities not carried at fair value: December 31, 2018 March 31, 2019 Carrying Value Fair Value Carrying Value Fair Value Fair Value Hierarchy Senior notes $ 746.2 $ 747.5 $ 746.4 $ 760.6 Level 2 Junior convertible securities 312.5 391.5 313.2 436.7 Level 2 Junior subordinated notes — — 271.3 275.3 Level 2

Goodwill and Acquired Client Re

Goodwill and Acquired Client Relationships	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Acquired Client Relationships	Goodwill and Acquired Client Relationships The following tables present the changes in the Company’s consolidated Affiliates’ Goodwill and components of Acquired client relationships (net): Goodwill Balance, as of December 31, 2018 $ 2,633.4 Foreign currency translation 9.0 Balance, as of March 31, 2019 $ 2,642.4 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, 2018 $ 1,292.5 $ (988.9 ) $ 303.6 $ 1,006.3 $ 1,309.9 Intangible amortization and impairments — (29.6 ) (29.6 ) — (29.6 ) Foreign currency translation 1.0 — 1.0 8.2 9.2 Balance, as of March 31, 2019 $ 1,293.5 $ (1,018.5 ) $ 275.0 $ 1,014.5 $ 1,289.5 Definite-lived acquired client relationships are amortized over their expected period of economic benefit. The Company recorded amortization expense within Intangible amortization and impairments in the Consolidated Statements of Income for these relationships of $23.2 million and $29.6 million for the three months ended March 31, 2018 and 2019 , respectively. Based on relationships existing as of March 31, 2019 , the Company estimates that its consolidated annual amortization expense will be approximately $120 million in 2019, approximately $90 million in 2020, and approximately $65 million in each of 2021, 2022 and 2023.

Equity Method Investments in Af

Equity Method Investments in Affiliates	3 Months Ended
	Mar. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments in Affiliates	Equity Method Investments in Affiliates The following table presents the change in Equity method investments in Affiliates (net): Equity Method Investments in Affiliates (Net) Balance, as of December 31, 2018 $ 2,791.0 Earnings 80.1 Intangible amortization and impairments (438.2 ) Distributions of earnings (96.5 ) Foreign currency translation (16.9 ) Investments in Affiliates 34.1 Divestments of Affiliates (28.8 ) Other (6.3 ) Balance, as of March 31, 2019 $ 2,318.5 Definite-lived acquired relationships at the Company’s equity method Affiliates are amortized over their expected period of economic benefit. The Company recognized amortization expense for these relationships of $30.0 million and $23.2 million for the three months ended March 31, 2018 and 2019 , respectively. Based on relationships existing as of March 31, 2019 , the Company estimates the annual amortization expense attributable to its equity method Affiliates will be approximately $90 million in each of 2019 and 2020, and approximately $85 million in each of 2021, 2022 and 2023. During the three months ended March 31, 2019, the Company recognized a $415.0 million expense to reduce the carrying value of one of its equity method Affiliates to its fair value. A series of precipitating events led the Company to conclude in March 2019 that the growth expectations of a U.S. credit alternative Affiliate of the Company had declined significantly, which the Company determined constituted a triggering event. The Affiliate’s flagship product has underperformed. The cumulative effect of associated redemptions and scaled-down fundraising expectations reduced expected asset and performance based fees and operating margin at the Affiliate. This led to a significant decrease in projected operating cash flows available to fund the Affiliate’s growth strategy, prompting a change in the strategic objectives of the Affiliate, including exiting the systematic equity business and reducing the number of new investment strategies being pursued. The Company determined that the estimated fair value of the Affiliate had declined meaningfully. Therefore, the Company performed a valuation to determine whether the fair value of the Affiliate had declined below its carrying value using a discounted cash flow analysis, a level 3 fair value measurement. The Company assumed projected compounded asset based fee growth over the first five years of (13)% , discount rates of 11% and 20% for asset and performance based fees, respectively, and a market participant tax rate of 25% . 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.

Lease Commitments

Lease Commitments	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Lease Commitments	Lease Commitments The Company and its Affiliates currently lease office space and equipment under various operating leasing arrangements. The following table presents total lease costs (net): For the Three Months Ended March 31, 2019 Operating lease costs $ 9.0 Short-term lease costs 0.5 Variable lease costs 0.1 Sublease income (1.0 ) Total lease costs (net) $ 8.6 For the three months ended March 31, 2019 , cash flows for operating leases were $8.9 million and there were no significant right-of-use assets obtained in exchange for new operating leases. As of March 31, 2019, the Company’s and its Affiliates’ weighted average operating lease term was 7.9 years and the weighted average operating lease discount rate was 4.1% . As of March 31, 2019, the maturity of lease liabilities were as follows: Operating Leases Remainder of 2019 $ 25.0 2020 37.0 2021 35.9 2022 27.9 2023 23.6 Thereafter 76.6 Total undiscounted lease liabilities (1) $ 226.0 __________________________ (1) Total undiscounted lease liabilities were $42.3 million greater than the operating leases recorded in Other liabilities primarily due to present value discounting. Both amounts exclude leases with initial terms of 12 months or less and leases that have not yet commenced. In connection with the Company’s adoption of ASU 2016-02, the Company was not required, and did not, update prior period disclosures from the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018 . The Company’s reported aggregate required minimum payments for operating leases having initial or non-cancelable lease terms greater than one year under the old standard as of December 31, 2018 were as follows: Year Required Minimum Payments 2019 $ 35.5 2020 36.9 2021 34.8 2022 27.7 2023 23.4 Thereafter 75.2

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions A prior owner of one of the Company’s consolidated Affiliates retained 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 presented in Other liabilities and were $49.7 million and $46.1 million as of December 31, 2018 and March 31, 2019 , respectively. 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. In addition, 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. The Company has related party transactions in association with its Affiliate equity transactions, as more fully described in Notes 15 and 16. The Company’s executive officers and directors may invest from time to time in funds advised by its Affiliates on substantially the same terms as other investors.

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation	Share-Based Compensation The following table presents share-based compensation expense: For the Three Months Ended March 31, 2018 2019 Share-based compensation $ 10.7 $ 8.8 Tax benefit 2.7 1.8 As of December 31, 2018 , the Company had unrecognized share-based compensation expense of $54.1 million . As of March 31, 2019 , the Company had unrecognized share-based compensation expense of $77.9 million , which will be recognized over a weighted average period of approximately two years (assuming no forfeitures). 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, 2018 0.5 $ 130.81 Options granted 0.0 110.02 Options exercised (0.0) 107.63 Options forfeited (0.0) 122.67 Unexercised options outstanding - March 31, 2019 0.5 130.54 3.7 Exercisable at March 31, 2019 0.4 129.01 3.4 For the three months ended March 31, 2018 and 2019, the Company granted stock options with fair values of $0.5 million in each period. Stock options generally vest over a period of three to four years and expire seven years after the grant date. All options have been granted with exercise prices equal to the closing price of the Company’s common stock on the grant date. In certain circumstances, option awards also require certain performance conditions to be satisfied in order for the options to be exercised. The fair value of options granted was estimated using the Black-Scholes option pricing model and were $53.81 and $33.58 , per option, for the three months ended March 31, 2018 and 2019 , respectively. The weighted average grant date assumptions used to estimate the fair value of options granted were as follows: For the Three Months Ended March 31, 2018 2019 Dividend yield 0.7 % 1.2 % Expected volatility 24.6 % 31.9 % Risk-free interest rate 2.6 % 2.6 % Expected life of options (in years) 5.7 5.7 Forfeiture rate — % — % 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, 2018 0.6 $ 172.74 Units granted 0.3 110.02 Units vested (0.2 ) 169.93 Units forfeited (0.0) 156.63 Unvested units - March 31, 2019 0.7 145.80 For the three months ended March 31, 2018 and 2019 , the Company granted restricted stock unit awards with fair values of $36.7 million and $32.6 million , respectively. These awards were valued based on the closing price of the Company’s common stock on the grant date and the number of awards expected to be delivered. Awards containing vesting conditions generally require service over a period of three to four years and may also require the satisfaction of certain performance conditions. In certain cases, awards with performance conditions may use structures whereby the number of shares of the Company’s common stock that an employee ultimately receives at vesting will be equal to the base number of restricted stock units granted, multiplied by a predetermined percentage determined in accordance with the Company’s attainment of certain pre-established performance measures and could be higher or lower than the original restricted stock unit grant. During the three months ended March 31, 2019, there were no changes in the Company’s estimate of the number of shares expected to be delivered.

Redeemable Non-Controlling Inte

Redeemable Non-Controlling Interests	3 Months Ended
	Mar. 31, 2019
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 and 15 years from the date the equity interest is received or on an annual basis following an Affiliate equity holder’s departure). Prior to becoming redeemable, the value of the Company’s Affiliate equity is presented within Non-controlling interests. Upon becoming redeemable, the value of these interests is reclassified and the current redemption value of these interests is presented as Redeemable non-controlling interests. Changes in the current redemption value are recorded to Additional paid-in capital. When the Company receives a put notice, and, therefore, has an unconditional obligation to repurchase Affiliate equity interests, they are reclassified to Other liabilities. The following table presents the changes in Redeemable non-controlling interests: Redeemable Non-controlling Interests Balance, as of December 31, 2018 (1) $ 833.7 Changes attributable to consolidated Affiliate sponsored investment products (84.5 ) Transfers to Other liabilities (54.6 ) Transfers from Non-controlling interests 47.3 Changes in redemption value 12.9 Balance, as of March 31, 2019 (1) $ 754.8 (1) As of December 31, 2018 and March 31, 2019 , Redeemable non-controlling interests includes consolidated Affiliate sponsored investment products primarily attributable to third-party investors of $91.0 million and $6.5 million , respectively.

Affiliate Equity

Affiliate Equity	3 Months Ended
	Mar. 31, 2019
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. For the three months ended March 31, 2018 and 2019 , distributions paid to Affiliate equity holders (non-controlling interests) were $112.4 million and $104.6 million , respectively. The Company periodically repurchases Affiliate equity interests from and issues Affiliate equity interests to its Affiliate partners and its officers. For the three months ended March 31, 2018 and 2019 , the amount of cash paid for repurchases was $14.5 million and $15.4 million , respectively. For the three months ended March 31, 2018 and 2019 , the total amount of cash received for issuances was $6.2 million and $9.4 million , respectively. Sales and repurchases of Affiliate equity generally occur at fair value; however, the Company also grants Affiliate equity to its Affiliate partners and its officers as a form of compensation. If the equity is issued for consideration below the fair value of the equity, or repurchased 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 March 31, 2018 2019 Controlling interest $ 2.6 $ 2.2 Non-controlling interests 16.8 8.5 Total $ 19.4 $ 10.7 The following table presents unrecognized Affiliate equity compensation expense: Controlling Interest Remaining Life Non-controlling Interests Remaining Life December 31, 2018 $ 38.7 5 years $ 118.3 6 years March 31, 2019 41.0 5 years 123.4 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 $16.2 million and $15.0 million as of December 31, 2018 and March 31, 2019 , respectively, and was included in Other assets. The total payable was $36.2 million and $75.4 million as of December 31, 2018 and March 31, 2019 , 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 recognized 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 settled during the applicable periods: For the Three Months Ended March 31, 2018 2019 Net income (loss) (controlling interest) $ 153.0 $ (200.8 ) Decrease in controlling interest paid-in capital from Affiliate equity issuances (1.0 ) (0.7 ) Decrease in controlling interest paid-in capital from Affiliate equity repurchases (33.1 ) (17.3 ) Net income (loss) (controlling interest) including the net impact of Affiliate equity transactions $ 118.9 $ (218.8 )

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
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 March 31, 2018 2019 Controlling interest: Current taxes $ 47.3 $ 21.1 Intangible-related deferred taxes 13.2 (93.8 ) Other deferred taxes 0.3 7.9 Total controlling interest 60.8 (64.8 ) Non-controlling interests: Current taxes $ 2.8 $ 3.1 Deferred taxes (0.1 ) (0.1 ) Total non-controlling interests 2.7 3.0 Income tax expense (benefit) $ 63.5 $ (61.8 ) Income (loss) before income taxes (controlling interest) $ 213.8 $ (265.6 ) Effective tax rate (controlling interest) (1) 28.4 % 24.4 % __________________________ (1) Taxes attributable to the controlling interest divided by Income (loss) before income taxes (controlling interest).

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The calculation of Earnings (loss) per share (basic) is based on the weighted average number of shares of the Company’s common stock outstanding during the period. Earnings (loss) per share (diluted) is similar to Earnings (loss) 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 March 31, 2018 2019 Numerator Net income (loss) (controlling interest) $ 153.0 $ (200.8 ) Interest expense on junior convertible securities, net of taxes 4.7 — Net income (loss) (controlling interest), as adjusted $ 157.7 $ (200.8 ) Denominator Average shares outstanding (basic) 54.6 51.9 Effect of dilutive instruments: Stock options and restricted stock units 0.2 — Junior convertible securities 2.2 — Average shares outstanding (diluted) 57.0 51.9 Average shares outstanding (diluted) in the table above excludes share-based awards that have not satisfied performance conditions and the anti-dilutive effect of the following: For the Three Months Ended March 31, 2018 2019 Stock options and restricted stock units 0.1 0.6 Junior convertible securities — 2.2 The Company may settle portions of its Affiliate equity purchases in shares of its common stock. Because it is the Company’s intention to settle these potential purchases in cash, the calculation of Average shares outstanding (diluted) excludes any potential dilutive effect from possible share settlements of Affiliate equity purchases. For the three months ended March 31, 2019 , the Company repurchased 0.9 million shares of its common stock at an average price per share of $106.09 .

Comprehensive Income

Comprehensive Income	3 Months Ended
	Mar. 31, 2019
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Comprehensive Income	Comprehensive Income The following tables present the tax effects allocated to each component of Other comprehensive income (loss): For the Three Months Ended March 31, 2018 2019 Pre-Tax Tax Benefit Net of Tax Pre-Tax Tax Benefit Net of Tax Foreign currency translation adjustment $ 29.1 $ — $ 29.1 $ (5.5 ) $ 13.0 $ 7.5 Change in net realized and unrealized gain on derivative financial instruments 0.3 — 0.3 1.2 — 1.2 Other comprehensive income (loss) $ 29.4 $ — $ 29.4 $ (4.3 ) $ 13.0 $ 8.7 The components of accumulated other comprehensive loss, net of taxes, were as follows: Foreign Currency Translation Adjustment Realized and Unrealized Gains (Losses) on Derivative Securities Total Balance, as of December 31, 2018 $ (188.0 ) $ (0.5 ) $ (188.5 ) Other comprehensive income before reclassifications 7.5 1.1 8.6 Amounts reclassified — 0.1 0.1 Net other comprehensive income 7.5 1.2 8.7 Balance, as of March 31, 2019 $ (180.5 ) $ 0.7 $ (179.8 ) In connection with the adoption of ASU 2018-02, the Company elected to reclassify to Retained earnings $6.6 million of tax effects stranded in Accumulated other comprehensive loss as a result of the enactment of the Tax Cuts and Jobs Act on December 22, 2017.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On May 6, 2019, the Company announced that it will acquire a minority equity interest in Garda Capital Partners LP, which is expected to close in the third quarter of 2019.

Accounting Standards and Poli_2

Accounting Standards and Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	The Consolidated Financial Statements of Affiliated Managers Group, Inc. (the “Company”) have been prepared in accordance with accounting principles generally accepted in the United States of America (“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. Certain reclassifications have been made to the prior period’s financial statements to conform to the current period’s presentation. 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, 2018 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 indicated
Use of Estimates	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.
Recently Adopted Accounting Standards	Recently Adopted Accounting Standards Effective January 1, 2019, the Company adopted the following new Accounting Standard Updates (“ASUs”): • ASU 2016-02, Leases (and related ASUs); • ASU 2018-02, Income Statement - Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income; and • ASU 2014-09, Revenue from Contracts with Customers (and related ASUs, effective for the Company’s equity method Affiliates) The adoption of ASU 2016-02 was the only ASU that had a significant impact on the Company’s Consolidated Financial Statements. The Company adopted ASU 2016-02 using a modified retrospective method and, as a result, recorded a lease liability of $190.8 million and after certain reclassifications, primarily related to accrued lease payments and unamortized lease incentives, a right-of-use asset of $163.6 million as of January 1, 2019. Additionally, the Company elected the transition practical expedients provided by ASU 2016-02, which allowed the Company to carryforward its historical lease classification. Having adopted ASU 2016-02, the Company updated its leases accounting policy as described below. For a complete list of significant accounting policies, see the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2018 . Leases Leases are classified as either operating leases or finance leases. The Company and its Affiliates currently lease office space and equipment primarily under operating lease arrangements. As these leases expire, it is expected that, in the normal course of business, they will be renewed or replaced. Whether a lease is classified as an operating lease or a finance lease, the Company and its Affiliates must record a right-of-use asset and a lease liability for all leases at the commencement date of the lease, other than for leases with an initial term of 12 months or less. As permitted under ASU 2016-02, the Company and its Affiliates elect not to record short-term leases with an initial lease term less than 12 months on the Company’s Consolidated Balance Sheets. Right-of-use assets and lease liabilities are reported in Other assets and Other liabilities, respectively, on the Consolidated Balance Sheets. A lease liability is initially and subsequently reported at the present value of the outstanding lease payments determined by discounting those lease payments over the remaining lease term using the incremental borrowing rate of the legal entity entering into the lease as of the commencement date. A right-of-use asset is initially reported at the present value of the corresponding lease liability plus any prepaid lease payments and initial direct costs of entering into the lease, and reduced by any lease incentives. Subsequently, a right-of-use asset is reported at the present value of the lease liability adjusted for any prepaid or accrued lease payments, remaining balances of any lease incentives received, unamortized initial direct costs of entering into the lease and any impairments of the right-of-use asset. The Company and its Affiliates test for possible impairments of right-of-use assets annually or more frequently whenever events or changes in circumstances indicate that the carrying value of a right-of-use asset may exceed its fair value. If the carrying value of the right-of-use asset exceeds its fair value, then the carrying value of the right-of-use asset is reduced to its fair value and the expense is recorded in Other expenses (net) on the Consolidated Statements of Income. Subsequent to an impairment, the carrying value of the right-of-use asset is amortized on a straight-line basis over the remaining lease term. Lease liabilities and right-of-use assets based on variable lease payments that depend on an index or rate are initially measured using the index or rate at the commencement date with any subsequent changes in variable lease payments reported in Other expenses (net) as incurred. Most lease agreements for office space that are classified as operating leases contain renewal options, rent escalation clauses or other lease incentives provided by the lessor. Lease expense is accrued to recognize lease escalation provisions and renewal options that are reasonably certain to be exercised, as well as lease incentives provided by the lessor, on a straight-line basis over the lease term and is reported in Other expenses (net). If a right-of-use asset is impaired, the lease expense is subsequently reported in Other expenses (net) as the straight-line amortization of the right-of-use asset and the accretion of the lease liability, thereby transitioning to a front-loaded expense recognition profile for the associated lease. The Company and its Affiliates combine lease and non-lease components for their office space leases and separate non-lease components for their equipment leases in calculating their lease liabilities. Sublease income is reported in Investment and other income on the Consolidated Statements of Income.
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 entity under the equity method. Other investments in which the Company does not have rights to exercise significant influence are recorded at fair value, with changes in fair value reflected within Investment and other income on the Consolidated Statements of 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 Affiliates’ 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 equity ownership is included in Net income (non-controlling interests) in the Consolidated Statements of Income. Undistributed earnings attributable to Affiliate managements’ equity ownership, along with their share of any tangible or intangible net assets, are presented within 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 on the Consolidated Balance Sheets. The Company periodically issues, sells and repurchases 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 within 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 (loss) (net) in the Consolidated Statements of Income and the carrying value of the Affiliate is reported in Equity method investments in Affiliates (net) in the Consolidated Balance Sheets. Any deferred taxes recorded upon acquisition of an equity method Affiliate are presented on a gross basis within Equity method investments in Affiliates (net) and Deferred income tax liability (net) in the Consolidated Balance Sheets. The Company’s share of income taxes incurred directly by Affiliates accounted for under the equity method is recorded within Income tax expense (benefit) in the Consolidated Statements of Income. The Company periodically evaluates its equity method Affiliates for impairment. In such impairment evaluations, the Company assesses whether or not the fair value of the investment has declined below its carrying value for a period considered to be other-than-temporary. If the Company determines that a decline in fair value below the carrying value of the investment is other-than-temporary, then the carrying value of the investment is reduced to its fair value and the expense is recorded in Equity method income (loss) (net). Affiliate Sponsored Investment Products The Company’s Affiliates sponsor various investment products where they also act 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 does not generally consolidate these products unless the Company’s or its consolidated Affiliate’s interest in the product is considered substantial. When the Company’s or its consolidated Affiliates’ interests are considered substantial and 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 in the Consolidated Balance Sheets, with corresponding changes in the investments’ fair values reflected in Investment and other income. Purchases and sales of securities are presented within purchases and sales by consolidated Affiliate sponsored investment products in the Consolidated Statements of Cash Flows 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.

Investments in Marketable Sec_2

Investments in Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2019
Marketable Securities [Abstract]
Schedule of Investments in Marketable Securities	The following is a summary of the cost, gross unrealized gains, and losses and fair value of Investments in marketable securities: December 31, March 31, Cost $ 126.8 $ 35.0 Unrealized gains 1.1 1.6 Unrealized losses (8.6 ) (0.2 ) Fair value $ 119.3 $ 36.4

Investments in Affiliates and_2

Investments in Affiliates and Affiliate Sponsored Investment Products (Tables)	3 Months Ended
	Mar. 31, 2019
Variable Interest Entities
Schedule of Unconsolidated Assets and Liabilities of Equity Method Investments and Company's Risk of Loss	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, 2018 March 31, 2019 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 $ 2,216.5 $ 1.1 $ 2,208.5 $ 0.6 The unconsolidated assets, net of liabilities and non-controlling interests of equity method Affiliates considered VIEs, and the Company’s carrying value and maximum exposure to loss, were as follows: December 31, 2018 March 31, 2019 Unconsolidated Carrying Value and Unconsolidated Carrying Value and Affiliates accounted for under the equity method $ 1,102.9 $ 2,277.8 $ 1,167.6 $ 1,822.9

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Schedule of Debt on the Consolidated Balance Sheets	The Company’s Debt consisted of the following: December 31, March 31, Senior bank debt $ 779.7 $ 459.7 Senior notes 742.5 742.8 Junior convertible securities 307.4 308.2 Junior subordinated notes — 270.0 Debt $ 1,829.6 $ 1,780.7

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Company's Derivative Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table summarizes the Company’s and its Affiliates’ derivative financial instruments measured at fair value on a recurring basis: December 31, 2018 March 31, 2019 Assets Liabilities Assets Liabilities Forward contracts $ 32.0 $ (1.4 ) $ 17.2 $ (0.0 ) Put options — (60.3 ) — (42.4 ) Call options 34.1 — 26.6 — Total $ 66.1 $ (61.7 ) $ 43.8 $ (42.4 )
Schedule of Effect of Derivative Financial Instruments on the Consolidated Statements of Comprehensive Income and Statements of Income	The following table summarizes the effect of the derivative financial instruments on the Consolidated Statements of Comprehensive Income and the Consolidated Statements of Income. For the three months ended March 31, 2018 , the Company and its Affiliates did not have any significant derivative financial instruments. For the Three Months Ended March 31, 2019 Gain (Loss) Recognized in Other Comprehensive Income Gain Recognized in Earnings from Excluded Components (1) Forward contracts $ (16.8 ) $ 3.5 Put options 17.9 — Call options (7.5 ) — Total $ (6.4 ) $ 3.5 (1) The excluded components of the forward contracts are recognized in earnings on a straight-line basis over the respective period of the contracts as a reduction to Interest expense on the Consolidated Statements of Income.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Assets and Liabilities Measured on a Recurring Basis	The following tables summarize the Company’s financial assets and liabilities that are measured at fair value on a recurring basis: Fair Value Measurements December 31, 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 marketable securities $ 119.3 $ 119.3 $ — $ — Derivative financial instruments (1) 5.8 — 5.8 — Financial Liabilities (2) Contingent payment arrangements $ 1.9 $ — $ — $ 1.9 Affiliate equity repurchase obligations 36.2 — — 36.2 Derivative financial instruments 1.4 — 1.4 — Fair Value Measurements March 31, 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 marketable securities $ 36.4 $ 36.4 $ — $ — Derivative financial instruments (1) 1.4 — 1.4 — Financial Liabilities (2) Contingent payment arrangements $ 2.0 $ — $ — $ 2.0 Affiliate equity repurchase obligations 75.4 — — 75.4 Derivative financial instruments 0.0 — 0.0 — __________________________ (1) Amounts are presented within Other assets. (2) Amounts are presented within Other liabilities.
Schedule of Changes in Level 3 Assets and Liabilities	The following table presents the changes in level 3 liabilities: For the Three Months Ended March 31, 2018 2019 Contingent Payment Arrangements Affiliate Equity Repurchase Obligations Contingent Payment Arrangements Affiliate Equity Repurchase Obligations Balance, beginning of period $ 9.4 $ 49.2 $ 1.9 $ 36.2 Net realized and unrealized losses (1) 0.4 — 0.1 — Purchases and issuances (2) — 45.6 — 54.6 Settlements and reductions — (15.4 ) — (15.4 ) Balance, end of period $ 9.8 $ 79.4 $ 2.0 $ 75.4 Net change in unrealized losses relating to instruments still held at the reporting date $ 0.4 $ — $ 0.3 $ — ___________________________ (1) Accretion expense for these arrangements is recorded in Interest expense. (2) Includes transfers from Redeemable non-controlling interests.
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, 2018 March 31, 2019 Valuation Techniques Unobservable Input Fair Value Range Weighted Average Fair Value Range Weighted Average Contingent payment arrangements Discounted cash flow Growth rates $ 1.9 7% 7% $ 2.0 7% 7% Discount rates 15% 15% 15% 15% Affiliate equity repurchase obligations Discounted cash flow Growth rates 36.2 (4)% - 9% 3% 75.4 (4)% - 9% 5% Discount rates 14% - 16% 15% 13% - 17% 15%
Schedule of Investments in Certain Entities that Calculate Net Asset Value	The following table summarizes the fair values of these investments and unfunded commitments: December 31, 2018 March 31, 2019 Category of Investment Fair Value Unfunded Commitments Fair Value Unfunded Commitments Private equity funds (1) $ 193.2 $ 131.0 $ 198.5 $ 146.6 Other funds (2) 7.9 — 9.0 — Other investments (3) $ 201.1 $ 131.0 $ 207.5 $ 146.6 ___________________________ (1) The Company uses NAV as a practical expedient one quarter in arrears (adjusted for current period calls and distributions) to determine the fair value. These funds primarily invest in a broad range of private equity funds, as well as making 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 long/short equity, credit and real estate. Investments are generally redeemable on a daily, monthly or quarterly basis. (3) Fair value attributable to the controlling interest was $123.2 million and $131.3 million as of December 31, 2018 and March 31, 2019 , respectively.
Schedule of 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, 2018 March 31, 2019 Carrying Value Fair Value Carrying Value Fair Value Fair Value Hierarchy Senior notes $ 746.2 $ 747.5 $ 746.4 $ 760.6 Level 2 Junior convertible securities 312.5 391.5 313.2 436.7 Level 2 Junior subordinated notes — — 271.3 275.3 Level 2

Goodwill and Acquired Client _2

Goodwill and Acquired Client Relationships (Tables)	3 Months Ended
	Mar. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Changes in Goodwill	The following tables present the changes in the Company’s consolidated Affiliates’ Goodwill and components of Acquired client relationships (net): Goodwill Balance, as of December 31, 2018 $ 2,633.4 Foreign currency translation 9.0 Balance, as of March 31, 2019 $ 2,642.4
Schedule of Changes in the Components of Acquired Client Relationships	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, 2018 $ 1,292.5 $ (988.9 ) $ 303.6 $ 1,006.3 $ 1,309.9 Intangible amortization and impairments — (29.6 ) (29.6 ) — (29.6 ) Foreign currency translation 1.0 — 1.0 8.2 9.2 Balance, as of March 31, 2019 $ 1,293.5 $ (1,018.5 ) $ 275.0 $ 1,014.5 $ 1,289.5

Equity Method Investments in _2

Equity Method Investments in Affiliates (Tables)	3 Months Ended
	Mar. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Changes in Equity Method Investments in Affiliates	The following table presents the change in Equity method investments in Affiliates (net): Equity Method Investments in Affiliates (Net) Balance, as of December 31, 2018 $ 2,791.0 Earnings 80.1 Intangible amortization and impairments (438.2 ) Distributions of earnings (96.5 ) Foreign currency translation (16.9 ) Investments in Affiliates 34.1 Divestments of Affiliates (28.8 ) Other (6.3 ) Balance, as of March 31, 2019 $ 2,318.5

Lease Commitments (Tables)

Lease Commitments (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Schedule of the Company's and its Affiliates' Total Lease Cost, Net	The following table presents total lease costs (net): For the Three Months Ended March 31, 2019 Operating lease costs $ 9.0 Short-term lease costs 0.5 Variable lease costs 0.1 Sublease income (1.0 ) Total lease costs (net) $ 8.6
Schedule of the Company's Maturity of Lease Liabilities	As of March 31, 2019, the maturity of lease liabilities were as follows: Operating Leases Remainder of 2019 $ 25.0 2020 37.0 2021 35.9 2022 27.9 2023 23.6 Thereafter 76.6 Total undiscounted lease liabilities (1) $ 226.0 __________________________ (1) Total undiscounted lease liabilities were $42.3 million greater than the operating leases recorded in Other liabilities primarily due to present value discounting. Both amounts exclude leases with initial terms of 12 months or less and leases that have not yet commenced.
Schedule Required Minimum Payments for Operating Leases Before Adoption of ASU 2016-02	The Company’s reported aggregate required minimum payments for operating leases having initial or non-cancelable lease terms greater than one year under the old standard as of December 31, 2018 were as follows: Year Required Minimum Payments 2019 $ 35.5 2020 36.9 2021 34.8 2022 27.7 2023 23.4 Thereafter 75.2

Share-Based Compensation (Table

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-Based Compensation	The following table presents share-based compensation expense: For the Three Months Ended March 31, 2018 2019 Share-based compensation $ 10.7 $ 8.8 Tax benefit 2.7 1.8
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, 2018 0.5 $ 130.81 Options granted 0.0 110.02 Options exercised (0.0) 107.63 Options forfeited (0.0) 122.67 Unexercised options outstanding - March 31, 2019 0.5 130.54 3.7 Exercisable at March 31, 2019 0.4 129.01 3.4
Schedule of Fair Value of Options Granted and Assumptions	The weighted average grant date assumptions used to estimate the fair value of options granted were as follows: For the Three Months Ended March 31, 2018 2019 Dividend yield 0.7 % 1.2 % Expected volatility 24.6 % 31.9 % Risk-free interest rate 2.6 % 2.6 % Expected life of options (in years) 5.7 5.7 Forfeiture rate — % — %
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, 2018 0.6 $ 172.74 Units granted 0.3 110.02 Units vested (0.2 ) 169.93 Units forfeited (0.0) 156.63 Unvested units - March 31, 2019 0.7 145.80

Redeemable Non-Controlling In_2

Redeemable Non-Controlling Interests (Tables)	3 Months Ended
	Mar. 31, 2019
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, 2018 (1) $ 833.7 Changes attributable to consolidated Affiliate sponsored investment products (84.5 ) Transfers to Other liabilities (54.6 ) Transfers from Non-controlling interests 47.3 Changes in redemption value 12.9 Balance, as of March 31, 2019 (1) $ 754.8 (1) As of December 31, 2018 and March 31, 2019 , Redeemable non-controlling interests includes consolidated Affiliate sponsored investment products primarily attributable to third-party investors of $91.0 million and $6.5 million , respectively.

Affiliate Equity (Tables)

Affiliate Equity (Tables)	3 Months Ended
	Mar. 31, 2019
Affiliate Equity [Abstract]
Schedule of Affiliate Equity Compensation	The following table presents Affiliate equity compensation expense: For the Three Months Ended March 31, 2018 2019 Controlling interest $ 2.6 $ 2.2 Non-controlling interests 16.8 8.5 Total $ 19.4 $ 10.7
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, 2018 $ 38.7 5 years $ 118.3 6 years March 31, 2019 41.0 5 years 123.4 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 settled during the applicable periods: For the Three Months Ended March 31, 2018 2019 Net income (loss) (controlling interest) $ 153.0 $ (200.8 ) Decrease in controlling interest paid-in capital from Affiliate equity issuances (1.0 ) (0.7 ) Decrease in controlling interest paid-in capital from Affiliate equity repurchases (33.1 ) (17.3 ) Net income (loss) (controlling interest) including the net impact of Affiliate equity transactions $ 118.9 $ (218.8 )

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2019
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 March 31, 2018 2019 Controlling interest: Current taxes $ 47.3 $ 21.1 Intangible-related deferred taxes 13.2 (93.8 ) Other deferred taxes 0.3 7.9 Total controlling interest 60.8 (64.8 ) Non-controlling interests: Current taxes $ 2.8 $ 3.1 Deferred taxes (0.1 ) (0.1 ) Total non-controlling interests 2.7 3.0 Income tax expense (benefit) $ 63.5 $ (61.8 ) Income (loss) before income taxes (controlling interest) $ 213.8 $ (265.6 ) Effective tax rate (controlling interest) (1) 28.4 % 24.4 % __________________________ (1) Taxes attributable to the controlling interest divided by Income (loss) before income taxes (controlling interest)

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Earnings 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 March 31, 2018 2019 Numerator Net income (loss) (controlling interest) $ 153.0 $ (200.8 ) Interest expense on junior convertible securities, net of taxes 4.7 — Net income (loss) (controlling interest), as adjusted $ 157.7 $ (200.8 ) Denominator Average shares outstanding (basic) 54.6 51.9 Effect of dilutive instruments: Stock options and restricted stock units 0.2 — Junior convertible securities 2.2 — Average shares outstanding (diluted) 57.0 51.9
Schedule of Shares Excluded from Calculation of Basic and Diluted Earnings Per Share	Average shares outstanding (diluted) in the table above excludes share-based awards that have not satisfied performance conditions and the anti-dilutive effect of the following: For the Three Months Ended March 31, 2018 2019 Stock options and restricted stock units 0.1 0.6 Junior convertible securities — 2.2

Comprehensive Income (Tables)

Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2019
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule of Tax Effects Allocated to Each Component of Other Comprehensive Income	The following tables present the tax effects allocated to each component of Other comprehensive income (loss): For the Three Months Ended March 31, 2018 2019 Pre-Tax Tax Benefit Net of Tax Pre-Tax Tax Benefit Net of Tax Foreign currency translation adjustment $ 29.1 $ — $ 29.1 $ (5.5 ) $ 13.0 $ 7.5 Change in net realized and unrealized gain on derivative financial instruments 0.3 — 0.3 1.2 — 1.2 Other comprehensive income (loss) $ 29.4 $ — $ 29.4 $ (4.3 ) $ 13.0 $ 8.7
Schedule of Components of Accumulated Other Comprehensive Income	The components of accumulated other comprehensive loss, net of taxes, were as follows: Foreign Currency Translation Adjustment Realized and Unrealized Gains (Losses) on Derivative Securities Total Balance, as of December 31, 2018 $ (188.0 ) $ (0.5 ) $ (188.5 ) Other comprehensive income before reclassifications 7.5 1.1 8.6 Amounts reclassified — 0.1 0.1 Net other comprehensive income 7.5 1.2 8.7 Balance, as of March 31, 2019 $ (180.5 ) $ 0.7 $ (179.8 )

Accounting Standards and Poli_3

Accounting Standards and Policies (Details) - ASU 2016-02 $ in Millions	Jan. 01, 2019USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Lease liability	$ 190.8
Right-of-use asset	$ 163.6

Investments in Marketable Sec_3

Investments in Marketable Securities - Cost, Gross Unrealized Gains and Losses and Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Marketable Securities [Abstract]
Cost	$ 35	$ 126.8
Unrealized gains	1.6	1.1
Unrealized losses	(0.2)	(8.6)
Fair value	$ 36.4	$ 119.3

Investments in Marketable Sec_4

Investments in Marketable Securities - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Proceeds received from sales of marketable securities	$ 15.1	$ 13.8
Net realized gains (losses) on sale of marketable securities	0.5	$ 2.8
Affiliate sponsored investment products
Investment [Line Items]
Fair value of deconsolidated investment in affiliate	$ 84.3

Investments in Affiliates and_3

Investments in Affiliates and Affiliate Sponsored Investment Products - Affiliated Accounted For Under Equity Method (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entities
Carrying value of equity method investment in affiliate	$ 2,318.5	$ 2,791
Carrying amount and maximum exposure to loss equity method investments considered VREs	495.6	513.2
Affiliates accounted for under the equity method
Variable Interest Entities
Unconsolidated VIE Net Assets	1,167.6	1,102.9
Carrying Value and Maximum Exposure to Loss	$ 1,822.9	$ 2,277.8

Investments in Affiliates and_4

Investments in Affiliates and Affiliate Sponsored Investment Products - Affiliated Sponsored Investment Products (Details) - Affiliate sponsored investment products - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entities
Unconsolidated VIE Net Assets	$ 2,208.5	$ 2,216.5
Carrying Value and Maximum Exposure to Loss	$ 0.6	$ 1.1

Debt - Summary of Company's Deb

Debt - Summary of Company's Debt (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt	$ 1,780.7	$ 1,829.6
Senior bank debt
Debt Instrument [Line Items]
Debt	459.7	779.7
Senior notes
Debt Instrument [Line Items]
Debt	742.8	742.5
Junior convertible securities
Debt Instrument [Line Items]
Debt	308.2	307.4
Junior subordinated notes
Debt Instrument [Line Items]
Debt	$ 270	$ 0

Debt - Additional Information (

Debt - Additional Information (Details) - USD ($)	Apr. 08, 2019	Mar. 27, 2019	Mar. 31, 2019	Jan. 18, 2019
Senior bank debt | Revolver
Debt Instrument [Line Items]
Total available borrowing				$ 1,250,000,000
Additional borrowing amount				500,000,000
Senior bank debt | Revolver | LIBOR
Debt Instrument [Line Items]
Basis spread on debt variable rate			1.10%
Senior bank debt | Term Loan
Debt Instrument [Line Items]
Total available borrowing				450,000,000
Additional borrowing amount				$ 75,000,000
Senior bank debt | Term Loan | LIBOR
Debt Instrument [Line Items]
Basis spread on debt variable rate			0.875%
Junior subordinated notes | 5.875% Junior Subordinated Notes Due 2059
Debt Instrument [Line Items]
Debt issued		$ 280,000,000
Debt interest rate		5.875%
Debt redemption price percentage of principal amount		100.00%
Debt redemption price percentage of principal amount plus unpaid and accrued interest		102.00%
Junior subordinated notes | 5.875% Junior Subordinated Notes Due 2059 | Subsequent Event
Debt Instrument [Line Items]
Debt issued	$ 300,000,000
Additional debt issued	$ 20,000,000
Junior subordinated notes | 5.875% Junior Subordinated Notes Due 2059 | On or after March 30, 2024
Debt Instrument [Line Items]
Debt redemption price percentage of principal amount		100.00%
Junior subordinated notes | 5.875% Junior Subordinated Notes Due 2059 | Prior to March 30, 2024
Debt Instrument [Line Items]
Debt redemption price percentage of principal amount		100.00%

Equity Distribution Program (De

Equity Distribution Program (Details) - Equity Distribution Program - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 27, 2019
Class of Stock [Line Items]
Equity distribution program, maximum amount authorized		$ 500,000,000
Sales of common stock under the equity distribution program	$ 0

Derivative Financial Instrume_3

Derivative Financial Instruments - Additional Information (Details) - Mar. 31, 2019 £ in Millions	USD ($)derivative$ / unit	GBP (£)derivative$ / unit
Derivative [Line Items]
Number of derivative contracts with contingent feature in a net liability position | derivative	0	0
Forward contracts
Derivative [Line Items]
Derivative, number of contracts | derivative	2	2
Cash collateral held from counterparty | $	$ 0
Cash collateral held at counterparty | $	$ 14,900,000
Collar contracts
Derivative [Line Items]
Derivative, number of contracts | derivative	2	2
Designated as Hedging Instrument | Net Investment Hedging | Forward contract expiring 2024
Derivative [Line Items]
Derivative notional amount	$ 400,000,000	£ 285.8
Designated as Hedging Instrument | Net Investment Hedging | Forward contract expiring 2021
Derivative [Line Items]
Derivative notional amount	$ 450,000,000	£ 325.3
Designated as Hedging Instrument | Net Investment Hedging | Collar contract-call option | Minimum
Derivative [Line Items]
Derivative, option strike price (in dollars per pound sterling)	1.288	1.288
Designated as Hedging Instrument | Net Investment Hedging | Collar contract-call option | Maximum
Derivative [Line Items]
Derivative, option strike price (in dollars per pound sterling)	1.535	1.535
Designated as Hedging Instrument | Net Investment Hedging | Collar contract-put option | Minimum
Derivative [Line Items]
Derivative, option strike price (in dollars per pound sterling)	1.318	1.318
Designated as Hedging Instrument | Net Investment Hedging | Collar contract-put option | Maximum
Derivative [Line Items]
Derivative, option strike price (in dollars per pound sterling)	1.448	1.448

Derivative Financial Instrume_4

Derivative Financial Instruments - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - Designated as Hedging Instrument - Derivatives in Net Investment Hedging Relationship - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Assets	$ 43.8	$ 66.1
Liabilities	(42.4)	(61.7)
Forward contracts
Derivative [Line Items]
Assets	17.2	32
Liabilities	0	(1.4)
Put options
Derivative [Line Items]
Assets	0	0
Liabilities	(42.4)	(60.3)
Call options
Derivative [Line Items]
Assets	26.6	34.1
Liabilities	$ 0	$ 0

Derivative Financial Instrume_5

Derivative Financial Instruments - Effect on Statement of Comprehensive Income and Statement of Income (Details) - Designated as Hedging Instrument - Derivatives in Net Investment Hedging Relationship $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Derivative [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income	$ (6.4)
Interest Expense
Derivative [Line Items]
Gain Recognized in Earnings from Excluded Components	3.5	[1]
Forward contracts
Derivative [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income	(16.8)
Forward contracts | Interest Expense
Derivative [Line Items]
Gain Recognized in Earnings from Excluded Components	3.5	[1]
Put options
Derivative [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income	17.9
Put options | Interest Expense
Derivative [Line Items]
Gain Recognized in Earnings from Excluded Components	0	[1]
Call options
Derivative [Line Items]
Gain (Loss) Recognized in Other Comprehensive Income	(7.5)
Call options | Interest Expense
Derivative [Line Items]
Gain Recognized in Earnings from Excluded Components	$ 0	[1]
[1]	The excluded components of the forward contracts are recognized in earnings on a straight-line basis over the respective period of the contracts as a reduction to Interest expense on the Consolidated Statements of Income.

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2019	Mar. 31, 2019
Commitments and Contingencies
Co-investment commitments in partnership		$ 146.6
Noncontrolling interest, sell of ownership percentage		5.00%
Equity Method Investee
Commitments and Contingencies
Contingent liability		$ 152.5
Equity Method Investee | Non-US
Commitments and Contingencies
Ownership percentage held by minority interest in affiliate to the Company		19.00%
Equity Method Investee | Subsequent Event | Non-US | Scenario, Forecast
Commitments and Contingencies
Payments to noncontrolling interest for additional equity interest in affiliate	$ 25.7

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		Mar. 31, 2019	Dec. 31, 2018
Financial Assets
Investments in marketable securities		$ 36.4	$ 119.3
Derivative financial instruments	[1]	1.4	5.8
Financial Liabilities
Contingent payment arrangements	[2]	2	1.9
Affiliate equity repurchase obligations	[2]	75.4	36.2
Derivative financial instruments	[2]	0	1.4
Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Assets
Investments in marketable securities		36.4	119.3
Derivative financial instruments	[1]	0	0
Financial Liabilities
Contingent payment arrangements	[2]	0	0
Affiliate equity repurchase obligations	[2]	0	0
Derivative financial instruments	[2]	0	0
Significant Other Observable Inputs (Level 2)
Financial Assets
Investments in marketable securities		0	0
Derivative financial instruments	[1]	1.4	5.8
Financial Liabilities
Contingent payment arrangements	[2]	0	0
Affiliate equity repurchase obligations	[2]	0	0
Derivative financial instruments	[2]	0	1.4
Significant Unobservable Inputs (Level 3)
Financial Assets
Investments in marketable securities		0	0
Derivative financial instruments	[1]	0	0
Financial Liabilities
Contingent payment arrangements	[2]	2	1.9
Affiliate equity repurchase obligations	[2]	75.4	36.2
Derivative financial instruments	[2]	$ 0	$ 0
[1]	Amounts are presented within Other assets.
[2]	Amounts are presented within Other liabilities.

Fair Value Measurements - Chang

Fair Value Measurements - Changes in Level 3 Assets and Liabilities (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Contingent Payment Arrangements
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period		$ 1.9	$ 9.4
Net realized and unrealized losses	[1]	0.1	0.4
Purchases and issuances	[2]	0	0
Settlements and reductions		0	0
Balance, end of period		2	9.8
Net change in unrealized losses relating to instruments still held at the reporting date		0.3	0.4
Affiliate Equity Repurchase Obligations
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period		36.2	49.2
Net realized and unrealized losses	[1]	0	0
Purchases and issuances	[2]	54.6	45.6
Settlements and reductions		(15.4)	(15.4)
Balance, end of period		75.4	79.4
Net change in unrealized losses relating to instruments still held at the reporting date		$ 0	$ 0
[1]	Accretion expense for these arrangements is recorded in Interest expense.
[2]	Includes transfers from Redeemable non-controlling interests.

Fair Value Measurements - Quant

Fair Value Measurements - Quantitative Information used in Valuing Level 3 Liabilities (Details) - Discounted Cash Flow $ in Millions	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Contingent Payment Arrangements | Growth rates
Quantitative information for Level 3 Fair Value Measurements Liabilities
Contingent payment arrangements, measurement input	0.07	0.07
Contingent Payment Arrangements | Growth rates | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Contingent payment arrangements, measurement input	0.07	0.07
Contingent Payment Arrangements | Discount rates
Quantitative information for Level 3 Fair Value Measurements Liabilities
Contingent payment arrangements, measurement input	0.15	0.15
Contingent Payment Arrangements | Discount rates | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Contingent payment arrangements, measurement input	0.15	0.15
Affiliate Equity Repurchase Obligations | Growth rates | Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	(0.04)	(0.04)
Affiliate Equity Repurchase Obligations | Growth rates | Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	0.09	0.09
Affiliate Equity Repurchase Obligations | Growth rates | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	0.05	0.03
Affiliate Equity Repurchase Obligations | Discount rates | Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	0.13	0.14
Affiliate Equity Repurchase Obligations | Discount rates | Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	0.17	0.16
Affiliate Equity Repurchase Obligations | Discount rates | Weighted Average
Quantitative information for Level 3 Fair Value Measurements Liabilities
Affiliate equity repurchase obligations, measurement input	0.15	0.15
Significant Unobservable Inputs (Level 3) | Contingent Payment Arrangements
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair value liabilities	$ 2	$ 1.9
Significant Unobservable Inputs (Level 3) | Affiliate Equity Repurchase Obligations
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair value liabilities	$ 75.4	$ 36.2

Fair Value Measurements - Inves

Fair Value Measurements - Investments Measured at Net Asset Value as Practical Expedient (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Dec. 31, 2018
NAV of investments at fair value
Life of funds (in years)		15 years
Other Investments
NAV of investments at fair value
Unfunded Commitments	[1]	$ 146.6	$ 131
Other Investments | Fair Value Measured at NAV
NAV of investments at fair value
Fair Value	[1]	207.5	201.1
Other Investments | Controlling Interest
NAV of investments at fair value
Fair Value		131.3	123.2
Private equity funds
NAV of investments at fair value
Unfunded Commitments	[2]	146.6	131
Private equity funds | Fair Value Measured at NAV
NAV of investments at fair value
Fair Value	[2]	198.5	193.2
Other funds
NAV of investments at fair value
Unfunded Commitments	[3]	0	0
Other funds | Fair Value Measured at NAV
NAV of investments at fair value
Fair Value	[3]	$ 9	$ 7.9
[1]	Fair value attributable to the controlling interest was $123.2 million and $131.3 million as of December 31, 2018 and March 31, 2019, respectively.
[2]	The Company uses NAV as a practical expedient one quarter in arrears (adjusted for current period calls and distributions) to determine the fair value. These funds primarily invest in a broad range of private equity funds, as well as making 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
[3]	These are multi-disciplinary funds that invest across various asset classes and strategies, including long/short equity, credit and real estate. Investments are generally redeemable on a daily, monthly or quarterly basis.

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities Not Carried at Fair Value (Details) - Level 2 - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	$ 746.4	$ 746.2
Junior convertible securities	313.2	312.5
Junior subordinated notes	271.3	0
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Senior notes	760.6	747.5
Junior convertible securities	436.7	391.5
Junior subordinated notes	$ 275.3	$ 0

Goodwill and Acquired Client _3

Goodwill and Acquired Client Relationships - Schedule of Changes in Goodwill (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Goodwill [Roll Forward]
Balance, as of December 31, 2018	$ 2,633.4
Foreign currency translation	9
Balance, as of March 31, 2019	$ 2,642.4

Goodwill and Acquired Client _4

Goodwill and Acquired Client Relationships - Schedule of Changes in the Components of Acquired Client Relationships (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Total
Beginning balance, net book value	$ 1,309.9
Ending balance, net book value	1,289.5
Acquired Client Relationships
Definite-lived
Beginning balance, gross book value	1,292.5
Beginning balance, accumulated amortization	(988.9)
Beginning balance, net book value	303.6
Amortization and impairments	(29.6)
Foreign currency translation	1
Ending balance, gross book value	1,293.5
Ending balance, accumulated amortization	(1,018.5)
Ending balance, net book value	275
Indefinite-lived
Beginning balance, net book value	1,006.3
Amortization and impairments	0
Foreign currency translation	8.2
Ending balance, net book value	1,014.5
Total
Beginning balance, net book value	1,309.9
Amortization and impairments	(29.6)
Foreign currency translation	9.2
Ending balance, net book value	$ 1,289.5

Goodwill and Acquired Client _5

Goodwill and Acquired Client Relationships - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Intangible Assets
Amortization and impairment expenses of intangible assets	$ 29.6	$ 23.2
Acquired Client Relationships
Estimated Future Amortization Expense of Finite-Lived Intangibles
Finite-lived intangible, future amortization expense in 2019	120
Finite-lived intangible, future amortization expense in 2020	90
Finite-lived intangible, future amortization expense in 2021	65
Finite-lived intangible, future amortization expense in 2022	65
Finite-lived intangible, future amortization expense in 2023	65
Acquired Client Relationships | Intangible amortization and impairments
Intangible Assets
Amortization and impairment expenses of intangible assets	$ 29.6	$ 23.2

Equity Method Investments in _3

Equity Method Investments in Affiliates - Change in Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Change in Equity Method Investments in Affiliates [Roll Forward]
Balance, as of December 31, 2018	$ 2,791
Distributions of earnings	(96.5)	$ (225.7)
Investments in Affiliates	34.1	$ 0
Balance, as of March 31, 2019	2,318.5
Equity Method Investee
Change in Equity Method Investments in Affiliates [Roll Forward]
Balance, as of December 31, 2018	2,791
Earnings	80.1
Intangible amortization and impairments	(438.2)
Distributions of earnings	(96.5)
Foreign currency translation	(16.9)
Investments in Affiliates	34.1
Divestments of Affiliates	(28.8)
Other	(6.3)
Balance, as of March 31, 2019	$ 2,318.5

Equity Method Investments in _4

Equity Method Investments in Affiliates - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Schedule of Equity Method Investments [Line Items]
Amortization expense during the period	$ 29.6	$ 23.2
Estimated Future Amortization Expense of Finite-Lived Intangibles
Impairment recognized on equity method investment	$ 415
Fair value assumptions, period of projected annual based fee margin growth rate	5 years
Fair value assumptions, projected annual based fee margin growth rate	(13.00%)
Fair value assumptions, discount rate for asset based fees	11.00%
Fair value assumptions, discount rate for performance based fees	20.00%
Fair value assumptions, market participant tax rate	25.00%
Acquired Client Relationships
Estimated Future Amortization Expense of Finite-Lived Intangibles
Finite-lived intangible, future amortization expense in 2019	$ 120
Finite-lived intangible, future amortization expense in 2020	90
Finite-lived intangible, future amortization expense in 2021	65
Finite-lived intangible, future amortization expense in 2022	65
Finite-lived intangible, future amortization expense in 2023	65
Equity Method Investee | Acquired Client Relationships
Schedule of Equity Method Investments [Line Items]
Amortization expense during the period	23.2	$ 30
Estimated Future Amortization Expense of Finite-Lived Intangibles
Finite-lived intangible, future amortization expense in 2019	90
Finite-lived intangible, future amortization expense in 2020	90
Finite-lived intangible, future amortization expense in 2021	85
Finite-lived intangible, future amortization expense in 2022	85
Finite-lived intangible, future amortization expense in 2023	$ 85

Lease Commitments - Total Lease

Lease Commitments - Total Lease Costs, Net (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Operating lease costs	$ 9
Short-term lease costs	0.5
Variable lease costs	0.1
Sublease income	(1)
Total lease costs (net)	$ 8.6

Lease Commitments - Additional

Lease Commitments - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Operating cash flows from operating leases	$ 8.9
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 0
Weighted average remaining lease term - operating leases	7 years 10 months 24 days
Weighted average discount rate - operating leases	4.10%

Lease Commitments - Maturity of

Lease Commitments - Maturity of Lease Liabilities (Details) $ in Millions	Mar. 31, 2019USD ($)
Leases [Abstract]
Remainder of 2019	$ 25
2020	37
2021	35.9
2022	27.9
2023	23.6
Thereafter	76.6
Total lease liabilities	226	[1]
Present value discounting of operating lease liabilities	$ 42.3
[1]	Total undiscounted lease liabilities were $42.3 million greater than the operating leases recorded in Other liabilities primarily due to present value discounting. Both amounts exclude leases with initial terms of 12 months or less and leases that have not yet commenced.

Lease Commitments - Required Mi

Lease Commitments - Required Minimum Payments for Operating Leases Before Adoption of ASU 2016-02 (Details) $ in Millions	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 35.5
2020	36.9
2021	34.8
2022	27.7
2023	23.4
Thereafter	$ 75.2

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Related Party Transactions
Other liabilities	$ 386.2	$ 162.7
Prior Owner | Private Equity Investment Partnerships of Affiliate
Related Party Transactions
Other liabilities	$ 46.1	$ 49.7

Share-Based Compensation - Shar

Share-Based Compensation - Share-Based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based compensation	$ 8.8	$ 10.7
Tax benefit	1.8	$ 2.7
Compensation expense related to share-based compensation	$ 77.9		$ 54.1
Weighted average period over which compensation expense will be recognized	2 years

Share-Based Compensation - Sche

Share-Based Compensation - Schedule of the Transactions of the Company's Stock Options (Details) shares in Millions	3 Months Ended
	Mar. 31, 2019$ / sharesshares
Stock Options
Unexercised options outstanding at the beginning of the period (in shares) | shares	0.5
Options granted (in shares) | shares	0
Options exercised (in shares) | shares	0
Options forfeited (in shares) | shares	0
Unexercised options outstanding at the end of the period (in shares) | shares	0.5
Exercisable at the end of the period (in shares) | shares	0.4
Weighted Average Exercise Price
Unexercised options outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 130.81
Options granted (in dollars per share) | $ / shares	110.02
Options exercised (in dollars per share) | $ / shares	107.63
Options forfeited (in dollars per share) | $ / shares	122.67
Unexercised options outstanding at the end of the period (in dollars per share) | $ / shares	130.54
Exercisable at the end of the period (in dollars per share) | $ / shares	$ 129.01
Weighted Average Remaining Contractual Life (Years)
Unexercised options outstanding at the end of the period (in years)	3 years 8 months 12 days
Exercisable at the end of the period (in years)	3 years 5 months 12 days

Share-Based Compensation - Sc_2

Share-Based Compensation - Schedule of Fair Value Options Granted and Assumptions (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation
Stock options granted, weighted average fair value (in dollars per share)	$ 33.58	$ 53.81
Stock Options
Share-based Compensation
Stock options granted, fair value	$ 0.5	$ 0.5
Stock options, expiration period (in years)	7 years
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Dividend yield	1.20%	0.70%
Expected volatility	31.90%	24.60%
Risk-fee interest rate	2.60%	2.60%
Expected life of options (in years)	5 years 8 months 12 days	5 years 8 months 12 days
Forfeiture rate	0.00%	0.00%
Stock Options | Minimum
Share-based Compensation
Stock options, vesting period (in years)	3 years
Stock Options | Maximum
Share-based Compensation
Stock options, vesting period (in years)	4 years

Share-Based Compensation - Sc_3

Share-Based Compensation - Schedule of Company Restricted Stock Units Transactions (Details) - Restricted Stock Units - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restricted Stock Units
Unvested units at the beginning of the period (in shares)	0.6
Units granted (in shares)	0.3
Units vested (in shares)	(0.2)
Units forfeited (in shares)	0
Unvested units at the end of the period (in shares)	0.7
Weighted Average Grant Date Value
Unvested units at the beginning of the period (in dollars per share)	$ 172.74
Units granted (in dollars per share)	110.02
Units vested (in dollars per share)	169.93
Units forfeited (in dollars per share)	156.63
Unvested units at the end of the period (in dollars per share)	$ 145.80
Restricted stocks granted, fair value	$ 32.6	$ 36.7
Minimum
Weighted Average Grant Date Value
Restricted stock, vesting period (in years)	3 years
Maximum
Weighted Average Grant Date Value
Restricted stock, vesting period (in years)	4 years

Redeemable Non-Controlling In_3

Redeemable Non-Controlling Interests (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Redeemable Noncontrolling Interest [Roll Forward]
Balance, as of December 31, 2018	[1]	$ 833.7
Changes attributable to consolidated Affiliate sponsored investment products		(84.5)
Transfers to Other liabilities		(54.6)
Transfers from Non-controlling interests		47.3	$ 4.9
Changes in redemption value		12.9
Balance, as of March 31, 2019	[1]	754.8
Affiliate sponsored investment products
Redeemable Noncontrolling Interest [Roll Forward]
Balance, as of December 31, 2018		91
Balance, as of March 31, 2019		$ 6.5
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
[1]	As of December 31, 2018 and March 31, 2019, Redeemable non-controlling interests includes consolidated Affiliate sponsored investment products primarily attributable to third-party investors of $91.0 million and $6.5 million, respectively.

Affiliated Equity - Additional

Affiliated Equity - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Affiliate Equity [Line Items]
Distributions paid to affiliate partners	$ 104.6	$ 112.4
Payments to acquire interest in affiliates	15.4	14.5
Issuance of interest in affiliates	9.4	$ 6.2
Other Assets
Affiliate Equity [Line Items]
Due from affiliates	15		$ 16.2
Other Liabilities
Affiliate Equity [Line Items]
Due to affiliates	$ 75.4		$ 36.2

Affiliate Equity - Summary of A

Affiliate Equity - Summary of Affiliate Recognized and Unrecognized Expense (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Affiliate Equity [Line Items]
Affiliate equity expense	$ 10.7	$ 19.4
Non- controlling Interests
Affiliate Equity [Line Items]
Non-controlling interests	$ 8.5	16.8
Unrecognized Affiliate Equity Expense [Abstract]
Remaining Life	6 years		6 years
Non-controlling Interests	$ 123.4		$ 118.3
Affiliated Entity
Affiliate Equity [Line Items]
Controlling interest	2.2	$ 2.6
Unrecognized Affiliate Equity Expense [Abstract]
Controlling Interest	$ 41		$ 38.7
Remaining Life	5 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
	Mar. 31, 2019	Mar. 31, 2018
Affiliate Equity [Abstract]
Net income (loss) (controlling interest)	$ (200.8)	$ 153
Decrease in controlling interest paid-in capital from Affiliate equity issuances	(0.7)	(1)
Decrease in controlling interest paid-in capital from Affiliate equity repurchases	(17.3)	(33.1)
Net income (loss) (controlling interest) including the net impact of Affiliate equity transactions	$ (218.8)	$ 118.9

Income Taxes - Schedule of Cons

Income Taxes - Schedule of Consolidated Provision for Income Taxes (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Income Tax Provision
Deferred taxes		$ (86)	$ 13.4
Income tax expense (benefit)		(61.8)	63.5
Non- controlling Interests
Income Tax Provision
Current taxes		3.1	2.8
Deferred taxes		(0.1)	(0.1)
Income tax expense (benefit)		3	2.7
Controlling Interest
Income Tax Provision
Current taxes		21.1	47.3
Intangible-related deferred taxes		(93.8)	13.2
Other deferred taxes		7.9	0.3
Income tax expense (benefit)		(64.8)	60.8
Income (loss) before income taxes (controlling interest)		$ (265.6)	$ 213.8
Effective tax rate (controlling interest)	[1]	24.40%	28.40%
[1]	Taxes attributable to the controlling interest divided by Income (loss) before income taxes (controlling interest).

Earnings Per Share - Schedule o

Earnings Per Share - Schedule of Basic and Diluted Earnings Per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator
Net income (loss) (controlling interest)	$ (200.8)	$ 153
Interest expense on junior convertible securities, net of taxes	0	4.7
Net income (loss) (controlling interest), as adjusted	$ (200.8)	$ 157.7
Denominator
Average shares outstanding (basic) (in shares)	51.9	54.6
Effect of dilutive instruments:
Stock options and restricted stock units (in shares)	0	0.2
Junior convertible securities (in shares)	0	2.2
Average shares outstanding (diluted) (in shares)	51.9	57

Earnings Per Share - Schedule_2

Earnings Per Share - Schedule of Shares Excluded from Calculation of Basic and Diluted Earnings Per Share (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
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)	0.6	0.1
Junior convertible securities
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	2.2	0

Earnings Per Share - Additional

Earnings Per Share - Additional Information (Details) shares in Millions	3 Months Ended
	Mar. 31, 2019$ / sharesshares
Earnings Per Share [Abstract]
Number or shares repurchased during period (in shares) | shares	0.9
Average price of shares repurchased during period (in dollars per share) | $ / shares	$ 106.09

Comprehensive Income - Summary

Comprehensive Income - Summary of the Tax Effects Allocated to Each Component of Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss)
Pre-Tax	$ (4.3)	$ 29.4
Tax Benefit (Expense)	13	0
Other comprehensive income, net of tax	8.7	29.4
Foreign currency translation adjustment
Accumulated Other Comprehensive Income (Loss)
Pre-Tax	(5.5)	29.1
Tax Benefit (Expense)	13	0
Other comprehensive income, net of tax	7.5	29.1
Change in net realized and unrealized gain on derivative financial instruments
Accumulated Other Comprehensive Income (Loss)
Pre-Tax	1.2	0.3
Tax Benefit (Expense)	0	0
Other comprehensive income, net of tax	$ 1.2	$ 0.3

Comprehensive Income - Schedule

Comprehensive Income - Schedule of Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Components of Accumulated other comprehensive income, net of taxes
Beginning Balance	$ 4,134.9	$ 4,578.5
Other comprehensive income, net of tax	8.7	29.4
Ending Balance	3,760.3	4,422.6
Foreign Currency Translation Adjustment
Components of Accumulated other comprehensive income, net of taxes
Beginning Balance	(188)
Other comprehensive income before reclassifications	7.5
Amounts reclassified	0
Other comprehensive income, net of tax	7.5	29.1
Ending Balance	(180.5)
Realized and Unrealized Gains (Losses) on Derivative Securities
Components of Accumulated other comprehensive income, net of taxes
Beginning Balance	(0.5)
Other comprehensive income before reclassifications	1.1
Amounts reclassified	0.1
Other comprehensive income, net of tax	1.2	$ 0.3
Ending Balance	0.7
Total
Components of Accumulated other comprehensive income, net of taxes
Beginning Balance	(188.5)
Other comprehensive income before reclassifications	8.6
Amounts reclassified	0.1
Other comprehensive income, net of tax	8.7
Ending Balance	$ (179.8)

Comprehensive Income - Addition

Comprehensive Income - Additional Information (Details) $ in Millions	Jan. 01, 2019USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax effects related to currency translation adjustments from AOCI to Retained Earnings	$ (6.6)
ASU 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax effects related to currency translation adjustments from AOCI to Retained Earnings	$ 6.6

Uncategorized Items - amg-20190

Label	Element	Value
Retained Earnings [Member]
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	amg_TaxCutsandJobsActReclassificationfromAOCItoRetainedEarningsTaxEffect	$ (6,600,000)