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Senior Notes

In 2017, the Company redeemed, canceled and retired all $200.0 million principal amount outstanding of its 6.375% senior unsecured notes due 2042 at a redemption price equal to 100% of the principal amount. At December 31, 2017, the Company had two senior notes outstanding and their respective principal terms are summarized in the following table:



	2024 Senior Notes			2025 Senior Notes
Issue date	February 2014			February 2015
Maturity date	February 2024			August 2025
Potential Call Date⁽¹⁾	Any Time			Any Time
Par value (in millions)	$	400.0		$	350.0
Call Price⁽¹⁾	As Defined			As Defined
Stated coupon	4.25		%	3.50		%
Coupon frequency	Semi-annually			Semi-annually

__________________________


⁽¹⁾	The senior notes may be redeemed at any time, in whole or in part, at a make-whole redemption price plus accrued and unpaid interest.

Convertible Securities

12 Months Ended

Dec. 31, 2017

Convertible Securities

At December 31, 2017, the Company had junior convertible trust preferred securities outstanding (the “junior convertible securities”). The carrying value and principal amount at maturity of the junior convertible securities were as follows:



	December 31, 2016				December 31, 2017
	Carrying Value		Principal Amount at Maturity		Carrying Value		Principal Amount at Maturity
Junior convertible securities⁽¹⁾	$	307.5	$	430.8	$	309.9	$	430.8

__________________________


⁽¹⁾	The carrying value is accreted to the principal amount at maturity over a remaining life of 20 years.

The junior convertible securities bear interest at a rate of 5.15% per annum, payable quarterly in cash. Each $50 security is convertible, at any time, into 0.25 shares of the Company’s common stock, which represents a conversion price of $200 per share, subject to customary anti-dilution adjustments. Holders of the junior convertible securities have no rights to put these securities to the Company. Upon conversion, holders will receive cash or shares of the Company’s common stock, or a combination thereof, at the Company’s election. The Company may redeem the junior convertible securities if the closing price of its common stock exceeds $260 per share for 20 trading days in a period of 30 consecutive trading days. The junior convertible securities are considered contingent payment debt instruments under federal income tax regulations, which require the Company to deduct interest in an amount greater than its reported interest expense. These deductions will generate annual deferred tax liabilities of $7.2 million. These deferred tax liabilities will be reclassified directly to stockholders’ equity if the Company’s common stock is trading above certain thresholds at the time of the conversion of the securities.

Forward Equity and Equity Distribution Program	12 Months Ended
Forward Equity and Equity Distribution Program	Dec. 31, 2017
Forward Equity Sale Agreements
Forward Equity and Equity Distribution Program	Forward Equity and Equity Distribution Program The Company has 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”). As of December 31, 2017, no sales have occurred under the equity distribution program. In 2016, the Company entered into an agreement to sell approximately 2.9 million shares of the Company’s common stock at a price of $167.25 per share on a forward basis and issued 2.7 million shares to settle a portion of this forward equity sale and received proceeds of $440.3 million, and net settled 0.2 million shares for cash at an average share price of $144.59. As of December 31, 2016, no shares remained outstanding under this agreement.

Derivative Financial Instruments	12 Months Ended
Derivative Financial Instruments	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments From time to time, the Company seeks to offset its exposure to interest rate and market changes and certain of its Affiliates seek to offset their exposure to changes in foreign exchange rates by entering into derivative contracts. For the years ended December 31, 2016 and 2017, the Company’s Affiliates realized $0.2 million and $1.6 million of gains, respectively, and $1.2 million and $2.2 million of losses, respectively, upon the settlement of certain foreign currency forward contracts. Such realized gains and losses are presented in Revenue, Operating expenses or Investment and other income, depending on the risk being hedged. At December 31, 2016 and 2017, the Company’s Affiliates had unrealized gains of $0.6 million and $0.2 million, respectively, and unrealized losses of $0.5 million and $0.6 million, respectively, related to outstanding foreign currency forward contracts. Such unrealized gains and losses are presented within Accumulated other comprehensive loss. During the fourth quarter of 2017, the Company recognized an expense of $2.5 million under a market based derivative contract. This contract expired on December 29, 2017.

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2017
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. In 2017, Third Avenue Management, LLC (“Third Avenue”) settled various legal actions relating to the liquidation and closure of the Third Avenue Focused Credit Fund, including those against the Company. Third Avenue and its insurers paid amounts due under the settlement. The Company has committed to co-invest in certain Affiliate sponsored investment products. As of December 31, 2017, these unfunded commitments were $98.8 million and may be called in future periods. As of December 31, 2017, the Company was contingently liable, upon achievement by certain Affiliates of specified financial targets, to make payments through 2019 related to the Company’s investments in these Affiliates. For its consolidated Affiliates, the Company was contingently liable for up to $18.2 million in payments, and expected to make payments of $10.2 million ($8.2 million in 2018). The present value of these expected payments was $9.4 million. For its equity method Affiliates, the Company was contingently liable to make payments up to $170.0 million through 2018, and expected to make no payments. Affiliate equity interests provide holders with a conditional right to put their interests to the Company over time. See Note 20. In addition, in connection with an investment in an 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 sell a portion of its ownership interest in the Affiliate to the Company annually beginning in the fourth quarter of 2018. The purchase price of these conditional purchases will be at fair market value on the date of the transaction. The Company and certain 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

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

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, 2016		Fair Value Measurements
	December 31, 2016		Level 1		Level 2		Level 3
Financial Assets
Cash equivalents	$	64.1	$	64.1	$	—	$	—
Investments in marketable securities⁽¹⁾
Trading securities	40.5		40.5		—		—
Available-for-sale securities	81.9		81.9		—		—
Other investments	3.4		3.4		—		—
Foreign currency forward contracts⁽²⁾	0.6		—		0.6		—
Financial Liabilities⁽²⁾
Contingent payment arrangements	$	8.6	$	—	$	—	$	8.6
Affiliate equity obligations	12.1		—		—		12.1
Foreign currency forward contracts	0.5		—		0.5		—



			Fair Value Measurements
	December 31, 2017		Fair Value Measurements
	December 31, 2017		Level 1		Level 2		Level 3
Financial Assets
Cash equivalents	$	40.4	$	40.4	$	—	$	—
Investments in marketable securities⁽¹⁾
Trading securities	57.2		57.2		—		—
Available-for-sale securities	20.6		20.6		—		—
Foreign currency forward contracts⁽²⁾	0.2		—		0.2		—
Financial Liabilities⁽²⁾
Contingent payment arrangements	$	9.4	$	—	$	—	$	9.4
Affiliate equity obligations	49.2		—		—		49.2
Foreign currency forward contracts	0.6		—		0.6		—

__________________________


⁽¹⁾	Principally investments in equity securities.

⁽²⁾Amounts are presented within Other assets or Other liabilities.

During 2017, the Company measured the fair value of one of its equity method investments using a discounted cash flow analysis. See Note 13.

The following are descriptions of the significant financial assets and liabilities measured at fair value and the fair value methodologies used.

Cash equivalents consist primarily of highly liquid investments in daily redeeming money market funds, without enacted liquidity fees or redemption gates that are valued at net asset value (“NAV”).

Investments in marketable securities consist primarily of investments in publicly traded securities and funds advised by Affiliates that are valued at NAV. Publicly traded securities valued using unadjusted quoted market prices for identical instruments in active markets are classified as level 1. Publicly traded securities valued using quoted prices for similar instruments in active markets or quoted prices for identical or similar instruments in markets that are not active are classified as level 2. Investments in funds advised by Affiliates that are valued at NAV are classified as level 1.

Contingent payment arrangements represent the present value of the expected future settlement of contingent payment arrangements related to the Company’s investments in consolidated Affiliates. The significant unobservable inputs that are used in the fair value measurement of these obligations are growth and discount rates. Increases in the growth rate result in a higher obligation while increases in the discount rate results in a lower obligation.

Affiliate equity obligations include agreements to repurchase Affiliate equity. The significant unobservable inputs that are used in the fair value measurement of the agreements to repurchase Affiliate equity are growth and discount rates. Increases in the growth rate result in a higher obligation while increases in the discount rate results in a lower obligation.

Foreign currency forward contracts use model-derived valuations in which all significant inputs are observable in active markets to determine fair value.

It is the Company’s policy to value financial assets or liabilities transferred as of the beginning of the period in which the transfer occurs. There were no significant transfers of financial assets or liabilities from level 1 to level 2 in 2016 or 2017.

Level 3 Financial Assets and Liabilities

The following tables present the changes in level 3 liabilities:



	For the Years Ended December 31,
	2016						2017
	Contingent Payment Arrangements			Affiliate Equity Obligations			Contingent Payment Arrangements			Affiliate Equity Obligations
Balance, beginning of period	$	10.2		$	62.3		$	8.6		$	12.1
Net realized and unrealized (gains) losses⁽¹⁾	(1.6		)	3.1			7.6			5.5
Purchases and issuances⁽²⁾	—			69.1			—			206.1
Settlements and reductions	—			(122.4		)	(6.8		)	(174.5		)
Balance, end of period	$	8.6		$	12.1		$	9.4		$	49.2

Net change in unrealized (gains) losses relating to instruments still held at the reporting date	$	(1.6	)	$	—		$	2.8		$	—

__________________________


⁽¹⁾	Accretion and changes in the expected value of the Company’s contingent payment arrangements and Affiliate equity obligations are recorded in Imputed interest expense and contingent payment arrangements.


⁽²⁾	Includes transfers from Redeemable non-controlling interests and other activity.

The following table presents certain quantitative information about the significant unobservable inputs used in valuing the Company’s level 3 financial liabilities:



	Quantitative Information about Level 3 Fair Value Measurements
	Valuation Techniques	Unobservable Input	Fair Value at December 31, 2016		Range at December 31, 2016	Fair Value at December 31, 2017		Range at December 31, 2017
Contingent payment arrangements	Discounted cash flow	Growth rates	$	8.6	3% - 8%	$	9.4	7% - 8%
		Discount rates			14% - 15%			15% - 16%
Affiliate equity obligations	Discounted cash flow	Growth rates	12.1		4% - 10%	49.2		0% - 11%
		Discount rates			15% - 16%			12% - 16%

Investments Measured at NAV as a Practical Expedient

The Company’s Affiliates sponsor investment products in which the Company and Affiliates may make general partner and seed capital investments. The Company uses the NAV of these investments as a practical expedient for their fair value. The following table summarizes the nature of the Company’s investments, unfunded commitments and any related liquidity restrictions or other factors that may impact the ultimate value realized:



	December 31, 2016				December 31, 2017
Category of Investment	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments
Private equity⁽¹⁾	$	137.8	$	92.2	$	156.1	$	98.8
Other funds⁽²⁾	9.7		—		8.9		—
Other investments⁽³⁾	$	147.5	$	92.2	$	165.0	$	98.8

__________________________


⁽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 $59.9 million and $80.1 million as of December 31, 2016 and 2017, respectively.

Other Financial Assets and Liabilities Not Carried at Fair Value

The carrying amount of 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, which is reported in Senior bank debt, approximates fair value because the debt has 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, 2016				December 31, 2017
	Carrying Value		Fair Value		Carrying Value		Fair Value		Fair Value Hierarchy
Senior notes	$	945.1	$	936.0	$	745.7	$	765.2	Level 2
Convertible securities	307.5		466.9		309.9		549.8		Level 2

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Acquired Client Relationships

12 Months Ended

Dec. 31, 2017

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
	2016			2017
Balance, as of January 1,	$	2,668.4		$	2,628.1
Foreign currency translation	(40.3		)	34.4
Balance, as of December 31,	$	2,628.1		$	2,662.5

As of September 30, 2017, the Company completed impairment assessments on its goodwill and no impairments were indicated.



	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, 2015	$	1,301.8		$	(680.4	)	$	621.4		$	1,065.0		$	1,686.4
Intangible amortization and impairments	—			(107.7		)	(107.7		)	(2.5		)	(110.2		)
Foreign currency translation	(11.8		)	—			(11.8		)	(67.0		)	(78.8		)
Balance, as of December 31, 2016	$	1,290.0		$	(788.1	)	$	501.9		$	995.5		$	1,497.4
Intangible amortization and impairments	—			(86.4		)	(86.4		)	—			(86.4		)
Foreign currency translation	5.5			—			5.5			33.2			38.7
Balance, as of December 31, 2017	$	1,295.5		$	(874.5	)	$	421.0		$	1,028.7		$	1,449.7

Definite-lived acquired client relationships are amortized over their expected period of economic benefit. The Company recorded amortization expense, in Intangible amortization and impairments, for these relationships of $115.4 million, $107.7 million and $86.4 million, respectively, for the years ended December 31, 2015, 2016 and 2017. Based on relationships existing as of December 31, 2017, the Company estimates that its consolidated annual amortization expense will be approximately $85 million in 2018 and 2019, $50 million in 2020 and $30 million in 2021 and 2022.

During 2017, the Company completed impairment assessments on its definite-lived and indefinite-lived acquired client relationships and no impairments were indicated.

The entire disclosure for the aggregate amount of goodwill and a description of intangible assets, which may include (a) for amortizable intangible assets (also referred to as finite-lived intangible assets), the carrying amount, the amount of any significant residual value, and the weighted-average amortization period, (b) for intangible assets not subject to amortization (also referred to as indefinite-lived intangible assets), the carrying amount, and (c) the amount of research and development assets acquired and written off in the period, including the line item in the income statement in which the amounts written off are aggregated, if not readily apparent from the income statement. Also discloses (a) for amortizable intangibles assets in total and by major class, the gross carrying amount and accumulated amortization, the total amortization expense for the period, and the estimated aggregate amortization expense for each of the five succeeding fiscal years, (b) for intangible assets not subject to amortization the carrying amount in total and by major class, and (c) for goodwill, in total and for each reportable segment, the changes in the carrying amount of goodwill during the period (including the aggregate amount of goodwill acquired, the aggregate amount of impairment losses recognized, and the amount of goodwill included in the gain (loss) on disposal of a reporting unit). If any part of goodwill has not been allocated to a reportable segment, discloses the unallocated amount and the reasons for not allocating. For each impairment loss recognized related to an intangible asset (excluding goodwill), discloses: (a) a description of the impaired intangible asset and the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method for determining fair value, (c) the caption in the income statement or the statement of activities in which the impairment loss is aggregated, and (d) the segment in which the impaired intangible asset is reported. For each goodwill impairment loss recognized, discloses: (a) a description of the facts and circumstances leading to the impairment, (b) the amount of the impairment loss and the method of determining the fair value of the associated reporting unit, and (c) if a recognized impairment loss is an estimate not finalized and the reasons why the estimate is not final. May also disclose the nature and amount of any significant adjustments made to a previous estimate of an impairment loss.

Equity Method Investments and Joint Ventures [Abstract]

Equity Method Investments in Affiliates

12 Months Ended

Dec. 31, 2017

Equity Investments in Affiliates

Equity Method Investments in Affiliates

In 2016, the Company completed investments in Systematica Investments L.P. and Baring Private Equity Asia, both of which closed on January 4, 2016, Capula Investment Management, LLP, Mount Lucas Management LP and Capeview Capital LLP, all of which closed on July 1, 2016, Partner Fund Management, L.P., which closed on September 30, 2016, and Winton Group Ltd., which closed on October 4, 2016. The purchase price allocations were completed using financial models that included assumptions of expected market performance, net client cash flows and discount rates. The majority of the consideration paid is deductible for U.S. tax purposes over a 15-year life. The financial results of certain equity method Affiliates are recognized in the Consolidated Financial Statements one quarter in arrears.

The purchase price allocation for the 2016 investments was as follows:



	Total
Definite-lived acquired client relationships⁽¹⁾	$	560.8
Indefinite-lived acquired client relationships	36.9
Tangible assets	2.0
Deferred tax liability	(91.8		)
Goodwill	854.4
Consideration paid	$	1,362.3

__________________________


⁽¹⁾	The expected period of economic benefit utilized in the purchase price allocation for these definite-lived acquired client relationships was 15 years.

For these new investments, the Company recorded amortization expense on the definite-lived acquired client relationships of $17.0 million and $58.0 million for the years ended December 31, 2016 and 2017, respectively.

The following table presents the change in Equity method investments in Affiliates:



	2016			2017
Balance, January 1,	$	1,937.1		3,368.3
Equity method earnings	388.0			501.4
Equity method intangible amortization and impairments	(59.2		)	(199.2		)
Distributions of earnings from equity method investments	(346.4		)	(429.8		)
Investments	1,361.3			29.8
Foreign currency translation	8.0			62.3
Other⁽¹⁾	79.5			(28.1		)
Balance, December 31,	$	3,368.3		$	3,304.7

__________________________


⁽¹⁾	Primarily reflects deferred income taxes recorded on new investments.

The 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 $34.3 million, $59.2 million and $106.1 million, respectively, for the years ended December 31, 2015, 2016 and 2017. Based on relationships existing as of December 31, 2017, the Company estimates the annual amortization expense attributable to its existing equity method Affiliates to be approximately $120 million in each of the next five years.

During 2017, the Company determined that the fair value of an equity method investment had declined below its carrying value. The decline in the fair value of this investment was the result of a cumulative decline in assets under management, coupled with the recent loss of a significant client, which has decreased the forecasted revenue of the firm. The fair value of the investment was determined using a discounted cash flow analysis, a level 3 fair value measurement, that projected future cash flows associated with the investment and discount rates that were developed with input from valuation experts. The significant assumptions used in the cash flow analysis include a projected growth rate of 10.0%, discount rates of 14.0% and 25.0% for asset and performance based fees, respectively, and a market participant tax rate of 25.0%. The Company considered the decline in fair value to be other-than-temporary and, accordingly, the Company recognized an impairment of $93.1 million. For the Company’s remaining equity and cost method investments, the Company completed its annual evaluation and no impairments were identified.

The following table presents summarized financial information for Affiliates accounted for under the equity method:



	For the Years Ended December 31,
	2015⁽²⁾		2016⁽²⁾		2017
Revenue⁽¹⁾	$	2,217.1	$	2,200.9	$	3,126.3
Net income⁽¹⁾	431.5		1,068.9		2,182.7



	December 31,
	2016		2017
Assets	$	1,915.3	$	3,324.9
Liabilities and Non-controlling interests	862.4		1,405.5

__________________________


⁽¹⁾	Revenue and the associated Net income include asset and performance based fees and the impact of consolidated investment products.


⁽²⁾	Revenue and Net income reflect investments in new Affiliates for the full-year, regardless of the date of the Company’s investment.

The Company’s share of undistributed earnings from equity method investments was $192.5 million as of December 31, 2017.

The Company has determined that one of its equity method Affiliates is significant under Rule 10-01(b)(1) of Regulation S-X. For the years ended December 31, 2016 and 2017, this equity method Affiliate recognized revenue of $944.1 million and $1,317.8 million, respectively, and net income of $529.0 million and $806.6 million, respectively.

Fixed Assets and Lease Commitments

12 Months Ended

Dec. 31, 2017

Fixed Assets and Lease Commitments [Abstract]

Fixed Assets and Lease Commitments

Fixed assets consisted of the following:



	December 31,
	2016			2017
Building and leasehold improvements	$	103.5		$	111.9
Software	52.5			50.8
Equipment	39.5			44.5
Furniture and fixtures	20.8			21.4
Land, improvements and other	17.9			18.7
Fixed assets, at cost	234.2			247.3
Accumulated depreciation and amortization	(124.1		)	(136.3		)
Fixed assets, net	$	110.1		$	111.0

The Company and its consolidated Affiliates lease office space and equipment for their operations. At December 31, 2017, the Company’s aggregate future minimum payments for operating leases having initial or non-cancelable lease terms greater than one year were payable as follows:



Year	Required Minimum Payments
2018	$	37.0
2019	33.9
2020	35.3
2021	33.6
2022	26.6
Thereafter	89.9

Consolidated rent expense for 2015, 2016 and 2017 was $36.3 million, $35.5 million and $37.5 million, respectively.

Payables and Accrued Liabilities

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Payables and Accrued Liabilities

Payables and accrued liabilities consisted of the following:



	December 31,
	2016		2017
Accrued compensation	$	418.5	$	472.5
Unsettled fund share payables	83.2		103.1
Accrued income taxes	87.7		93.0
Accrued share repurchases	—		23.1
Accrued professional fees	26.1		22.5
Other	113.8		93.0
Payables and accrued liabilities	$	729.3	$	807.2

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions A prior owner of one of the Company’s Affiliates retained an interest in certain of the Affiliate’s private equity investment partnerships. The prior owner’s interest is presented in the Company’s Consolidated Balance Sheets as either a liability in Other liabilities or as Non-controlling interests, depending on the structure of the prior owner’s investments in the partnerships. The total liability was $67.8 million and $61.2 million at December 31, 2016 and 2017, respectively. The total non-controlling interest was $2.5 million at December 31, 2016. The Company and its Affiliates earn asset and performance based fees, distribution and servicing and other fees and incur distribution and servicing and other expenses for services provided to Affiliate sponsored investment products. In addition, Affiliate management owners and Company officers may serve as trustees or directors of certain investment vehicles from which the Company or an Affiliate earns fees. The Company had liabilities to related parties for contingent payment arrangements in connection with certain business combinations. The net present value of the total amounts payable were $8.6 million and $9.4 million as of December 31, 2016 and 2017, respectively, and were included in Other liabilities. In 2016, there were no payments made associated with these liabilities. In 2017, the Company made $6.8 million in such payments. For the years ended December 31, 2016 and 2017, the Company adjusted its estimates of contingent payment obligations and recorded gains attributable to the controlling interest of $2.8 million and expenses from adjustments to its contingent payment obligations of $6.6 million, respectively. These amounts are included in Imputed interest expense and contingent payment arrangements. The Company has related party transactions in association with its Affiliate equity transactions, as more fully described in Notes 19 and 20.

Stockholders' Equity

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stockholders' Equity

Stockholders’ Equity

Common Stock

The Company is authorized to issue up to 150.0 million shares of Voting Common Stock and 3.0 million shares of Class B Non-Voting Common Stock. As more fully described in Note 8, the Company is party to an equity distribution program under which the Company may sell shares of its common stock.

The Company’s Board of Directors authorized share repurchase programs in January 2017 and May 2015, authorizing the Company to repurchase up to 1.9 million and 3.0 million shares of its common stock, respectively, and these authorizations have no expiry. In 2017, the Company repurchased 2.4 million shares of this total authorized amount, at an average price per share of $173.19. As of December 31, 2017, 1.6 million shares remained available for repurchase under the January 2017 Plan and no shares remained available for repurchase under the May 2015 Plan. See Note 27.

The following is a summary of the Company’s share repurchase activity for the years ended December 31, 2015, 2016 and 2017:



Year	Shares Repurchased	Average Price
2015	1.7	$	209.39
2016	0.2	161.16
2017	2.4	173.19

Preferred Stock

The Company is authorized to issue up to 5.0 million shares of Preferred Stock. Any such Preferred Stock issued by the Company may rank prior to common stock as to dividend rights, liquidation preference or both, may have full or limited voting rights and may be convertible into shares of common stock.

Financial Instruments

The Company’s junior convertible securities contain an embedded right for holders to receive shares of the Company’s common stock under certain conditions. These arrangements, as well as the equity distribution program, meet the definition of equity and are not required to be accounted for separately as derivative instruments.

Share-Based Compensation

12 Months Ended

Dec. 31, 2017

Share-Based Compensation

Share-Based Incentive Plans

The Company has established various plans under which it is authorized to grant restricted stock, restricted stock units, stock options and stock appreciation rights. The Company may also grant cash awards that can be notionally invested in one or more specified measurement funds, including the Company’s common stock. Awards granted under the Company’s share-based incentive plans typically participate in any dividends declared, but such amounts are deferred until delivery of the shares and are forfeitable if the requisite service is not satisfied. Dividends may be paid in cash or may be reinvested in the Company’s common stock.

The total fair value of share-based compensation awards that vested was $27.4 million, $20.7 million and $59.4 million during the years ended December 31, 2015, 2016 and 2017, respectively.

Share-Based Incentive Compensation

The following is a summary of share-based compensation expense for the years ended December 31, 2015, 2016 and 2017:



Year	Share-Based Compensation Expense		Tax Benefit
2015	$	34.2	$	13.2
2016	39.2		15.1
2017	40.4		13.6

The excess tax benefit recognized from share-based incentive plans was $5.1 million and $10.9 million during the years ended December 31, 2016 and 2017, respectively, and classified as an operating cash flow.

The Company had $66.4 million and $63.5 million of unrecognized share-based compensation as of December 31, 2016 and 2017, respectively, which will be recognized over a weighted average period of approximately two years (assuming no forfeitures).

Stock Options

The following table summarizes the transactions of the Company’s stock options:



	Stock Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)
Unexercised options outstanding—January 1, 2017	1.4		$	108.53
Options granted	0.0		168.60
Options exercised	(0.7	)	97.54
Options forfeited	(0.1	)	140.26
Unexercised options outstanding—December 31, 2017	0.6		122.04		3.9
Exercisable at December 31, 2017	0.2		115.74		1.7

The Company granted stock options with fair values of $1.0 million, $16.4 million and $0.8 million in 2015, 2016 and 2017, respectively. 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 Company generally uses treasury stock to settle stock option exercises. The total intrinsic value of options exercised during the years ended December 31, 2015, 2016 and 2017 was $130.2 million, $27.7 million and $50.8 million, respectively. The cash received for options exercised was $25.6 million and $41.9 million during the years ended December 31, 2016 and 2017, respectively. As of December 31, 2017, the intrinsic value of exercisable options outstanding was $20.1 million, and 3.1 million options were available for grant under the Company’s option plans.

The fair value of options granted was estimated using the Black-Scholes option pricing model. The weighted average fair value of options granted during the years ended December 31, 2015, 2016 and 2017 was $54.92, $39.02 and $48.05, per option, respectively, based on the weighted-average grant date assumptions stated below.



	For the Years Ended December 31,
	2015		2016		2017
Dividend yield	0.0	%	0.0	%	0.5	%
Expected volatility⁽¹⁾	26.7	%	30.7	%	28.0	%
Risk-free interest rate⁽²⁾	1.5	%	1.6	%	2.1	%
Expected life of options (in years)⁽³⁾	5.0		5.7		5.7
Forfeiture rate	0.0	%	0.0	%	0.0	%

__________________________


⁽¹⁾	Expected volatility is based on historical and implied volatility.


⁽²⁾	Risk-free interest rate is based on the U.S. Treasury yield curve in effect at the date of grant.


⁽³⁾	Expected life of options (in years) is based on the Company’s historical and expected exercise behavior.

Restricted Stock

The following table summarizes the transactions of the Company’s restricted stock:



	Restricted Stock		Weighted Average Grant Date Value
Unvested units—January 1, 2017	0.6		$	168.84
Units granted	0.2		152.99
Units vested	(0.4	)	166.22
Units forfeited	(0.0	)	170.39
Unvested units—December 31, 2017	0.4		162.32

The Company granted awards with fair values of $50.7 million, $28.0 million and $36.9 million in 2015, 2016 and 2017, respectively. These awards were valued based on the closing price of the Company’s common stock on the grant date and contain vesting conditions requiring service over a period of three to four years. In certain circumstances, awards also require certain performance conditions to be satisfied.

As of December 31, 2017, the Company had 1.1 million shares available for grant under its plans.

Redeemable Non-Controlling Interests

12 Months Ended

Dec. 31, 2017

Noncontrolling Interest [Abstract]

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). The current redemption value of the Company’s Affiliate equity interests is presented as Redeemable non-controlling interests. Changes in the current redemption value are recorded to Additional paid-in capital. When the Company 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:



	December 31,
	2016			2017
Balance, as of January 1,	$	612.5		$	673.5
Changes attributable to consolidated products	16.1			12.4
Transfers to Other liabilities	(69.1		)	(192.3		)
Transfers from non-controlling interests	42.6			76.8
Changes in redemption value	71.4			241.5
Balance, as of December 31,	$	673.5		$	811.9

Affiliate Equity

12 Months Ended

Dec. 31, 2017

Affiliate Equity

Affiliate Equity

Affiliate equity interests are allocated income in a manner that is consistent with the structured partnership interests in place at the respective Affiliate. The Company’s Affiliates generally pay quarterly distributions to Affiliate equity holders. Distributions paid to Affiliate equity holders were $431.4 million, $354.1 million and $352.2 million for the years ended December 31, 2015, 2016 and 2017, respectively.

Affiliate equity interests provide the Company a conditional right to call (on an annual basis following an Affiliate equity holder’s departure) and Affiliate equity holders have a conditional right to put their interests 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). Affiliate equity holders are also permitted to sell their equity interests to other individuals or entities in certain cases, subject to the Company's approval or other restrictions. The purchase price of these conditional purchases are generally calculated based upon a multiple of cash flow distributions, which is intended to represent fair value. The Company, at its option, may pay for Affiliate equity purchases in cash, shares of its common stock or other forms of consideration and can consent to the transfer of these interests to other individuals or entities.

The Company periodically repurchases Affiliate equity interests from and issues Affiliate equity interests to its Affiliate partners, its employees and its officers. The amount of cash paid for repurchases was $130.8 million, $115.8 million and $174.7 million for the years ended December 31, 2015, 2016 and 2017, respectively. The total amount of cash received for issuances was $6.1 million, $11.8 million and $9.0 million for the years ended December 31, 2015, 2016 and 2017, respectively.

Sales and repurchases of Affiliate equity generally occur at fair value; however, the Company also grants Affiliate equity to its Affiliate partners, its employees 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, then such difference is recorded as compensation expense over the requisite service period.

The following is a summary of Affiliate equity expense:



	For the Years Ended December 31,
	2015		2016		2017
Controlling interest	$	16.9	$	10.0	$	13.2
Non-controlling interest	51.6		31.2		36.8
Total	$	68.5	$	41.2	$	50.0

The following is a summary of unrecognized Affiliate equity expense for the years ended December 31, 2015, 2016 and 2017:



	Unrecognized Affiliate Equity Expense
Year	Controlling Interest		Remaining Life	Non-Controlling Interest		Remaining Life
2015	$	22.4	3 years	$	51.9	5 years
2016	31.3		4 years	70.7		5 years
2017	33.3		5 years	95.9		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 $22.9 million and $12.4 million at December 31, 2016 and 2017, respectively, and was included in Other assets. The total payable was $12.1 million and $49.2 million as of December 31, 2016 and 2017, 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 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 discloses the cumulative effect that ownership changes had on the controlling interest’s equity related only to Affiliate equity transactions that settled during the periods:



	For the Years Ended December 31,
	2015			2016			2017
Net income (controlling interest)	$	509.5		$	472.8		$	689.5
Increase / (decrease) in controlling interest paid-in capital from purchases and sales of Affiliate equity issuances	0.9			1.6			(1.0		)
Decrease in controlling interest paid-in capital related to Affiliate equity repurchases	(87.6		)	(38.0		)	(116.2		)
Net income attributable to controlling interest and transfers from non-controlling interests	$	422.8		$	436.4		$	572.3

Benefit Plans	12 Months Ended
Benefit Plans	Dec. 31, 2017
Retirement Benefits [Abstract]
Benefit Plans	Benefit Plans The Company has a defined contribution plan that is a qualified employee profit-sharing plan, covering substantially all of its employees. Under this plan, the Company is able to make discretionary contributions for the benefit of its employees that are qualified plan participants, up to Internal Revenue Service limits. The Company’s consolidated Affiliates have their own qualified defined contribution retirement plans covering their respective employees or, for several Affiliates, have their employees covered under the Company’s plan. In each case, the relevant Affiliate is able to make discretionary contributions for the benefit of its employees, as applicable, that are qualified plan participants, up to Internal Revenue Service limits. Consolidated expenses related to these plans were $18.7 million, $18.9 million and $20.1 million for the years ended December 31, 2015, 2016 and 2017, respectively. The controlling interest’s portion of expenses related to these plans were $3.1 million, $3.7 million and $3.9 million for the years ended December 31, 2015, 2016 and 2017, respectively.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

As of December 31, 2017, the Company had not completed its accounting for the tax effects of changes in U.S. tax laws. However, in accordance with SAB 118, the Company recorded a provisional one-time net benefit of $194.1 million as a reasonable estimate of the impacts of the changes in U.S. tax laws. The net benefit was primarily due to the re-measurement of the Company’s deferred tax assets and liabilities, principally deferred tax liabilities associated with its intangible assets and convertible securities, which resulted in a benefit of $216.9 million, partially offset by a $22.8 million transition tax on its deemed repatriated foreign earnings and profits.

The Company is still analyzing certain aspects of the changes in U.S. tax laws and evaluating its calculations, which could potentially affect the re-measurement of its deferred tax assets and liabilities or give rise to new deferred tax amounts. The Company has also not yet completed its accounting for the transition tax and the amount may change once the Company finalizes its calculation of foreign earnings and profits previously deferred from U.S. federal taxation and the amounts held in cash or other specified assets.

The provisional amounts recorded by the Company are based on guidance, interpretations and other information available as of January 24, 2018. The impact of the changes in U.S. tax laws may be refined as further guidance, interpretations or information becomes available or upon completion by the Company of its evaluation of the impact of the changes in U.S. tax laws.

The Company’s consolidated income tax provision includes taxes attributable to the controlling interest and, to a lesser extent, taxes attributable to non-controlling interests. The 2017 provisional impact of the changes in U.S. tax laws is reflected in the tables below.

The following table presents our consolidated provision for income taxes:



	For the Years Ended December 31,
	2015			2016			2017
Controlling interests:
Current tax	$	152.4		$	168.1		$	173.8
Intangible-related deferred taxes	77.7			84.3			(98.5		)
Other deferred taxes	27.7			(23.2		)	(24.9		)
Total controlling interests	257.8			229.2			50.4
Non-controlling interests:
Current tax	$	9.8		$	8.2		$	8.2
Deferred taxes	(4.2		)	(1.8		)	(0.2		)
Total non-controlling interests	5.6			6.4			8.0
Provision for income taxes	$	263.4		$	235.6		$	58.4
Income before income taxes (controlling interest)	$	767.3		$	702.0		$	739.9
Effective tax rate attributable to controlling interests⁽¹⁾	33.6		%	32.6		%	6.8		%

__________________________


⁽¹⁾	Taxes attributable to the controlling interest divided by Income before income taxes (controlling interest).

The consolidated provision for income taxes consisted of the following:



	For the Years Ended December 31,
	2015			2016			2017
Current:
Federal	$	106.3		$	103.4		$	109.0
State	18.3			22.9			18.9
Foreign	37.6			50.0			54.1
Total current	162.2			176.3			182.0
Deferred:
Federal	103.8			62.3			(124.9		)
State	14.8			10.0			10.4
Foreign	(17.4		)	(13.0		)	(9.1		)
Total deferred	101.2			59.3			(123.6		)
Provision for income taxes	$	263.4		$	235.6		$	58.4

For financial reporting purposes, Income before income taxes consisted of the following:



	For the Years Ended December 31,
	2015		2016		2017
Domestic	$	827.6	$	688.1	$	756.5
International	263.0		286.5		310.6
	$	1,090.6	$	974.6	$	1,067.1

The following table reconciles the U.S. federal statutory tax rate to the Company’s effective tax rate:



	For the Years Ended December 31,
	2015		2016		2017
Statutory U.S. federal tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal benefit	2.6		2.9		2.7
Effect of foreign operations	(3.5	)	(4.6	)	(5.4	)
Equity compensation	0.8		(0.4	)	(0.7	)
Effect of changes in tax law, rates	(0.8	)	(0.3	)	(25.2	)
Other	(0.5	)	—		0.4
Effective tax rate (controlling interest)	33.6	%	32.6	%	6.8	%
Effect of income from non-controlling interests	(9.2	)	(8.4	)	(1.3	)
Effective tax rate	24.4	%	24.2	%	5.5	%

Deferred income tax liability (net) reflects the expected future tax consequences of temporary differences between the financial reporting basis and tax basis of the Company’s assets and liabilities. The significant components of the Company’s Deferred income tax liability (net) are as follows:



	December 31,
	2016			2017
Deferred Tax Assets
State net operating loss carryforwards	$	17.4		$	16.8
Foreign loss carryforwards	14.6			16.3
Tax benefit of uncertain tax positions	12.1			11.4
Deferred compensation	34.1			10.4
Foreign tax credits	10.0			—
Accrued expenses	3.9			1.3
Total deferred tax assets	92.1			56.2
Valuation allowance	(22.1		)	(24.1		)
Deferred tax assets, net of valuation allowance	$	70.0		$	32.1
Deferred Tax Liabilities
Intangible asset amortization	$	(396.8	)	$	(258.6	)
Non-deductible intangible amortization	(177.0		)	(150.8		)
Convertible securities interest	(109.0		)	(77.9		)
Deferred income	(47.2		)	(5.9		)
Other	(0.8		)	(6.3		)
Total deferred tax liabilities	(730.8		)	(499.5		)
Deferred income tax liability (net)	$	(660.8	)	$	(467.4	)

At December 31, 2017, the Company had available state net operating loss carryforwards of $432.6 million, which will expire over a 19-year period. At December 31, 2017, the Company had foreign loss carryforwards of $61.5 million, of which $51.8 million will expire over a 20-year period and the balance will carry forward indefinitely.

The Company believes that it is more-likely-than-not that the benefit from a portion of the state and foreign loss carryforwards will not be realized and has, therefore, recorded a valuation allowance of $24.1 million on the deferred tax assets related to these state and foreign loss carryforwards. For the years ended December 31, 2016 and 2017, the Company increased its valuation allowance $1.6 million and $2.0 million, respectively, related to an increase in the loss carryforwards that are not expected to be realized.

The Company continues not to provide for U.S. income taxes on the excess of the financial reporting basis over tax basis in the Company’s investments in foreign subsidiaries considered permanent in duration. Such amount would generally become taxable upon the repatriation of assets from, or a sale or liquidation of, the subsidiaries. While a determination of the potential amount of unrecognized deferred U.S. income tax liability related to these amounts is not practicable because of the numerous assumptions associated with this hypothetical calculation, as of December 31, 2017, the estimated amount of such difference was $270.9 million.

A reconciliation of the changes in unrecognized tax benefits is as follows:



	For the Years Ended December 31,
	2015			2016			2017
Balance, as of January 1,	$	28.8		$	26.9		$	26.8
Additions based on current year tax positions	2.2			3.8			6.0
Additions based on prior years’ tax positions	1.6			0.6			1.5
Reductions related to lapses of statutes of limitations	(4.3		)	(4.7		)	(2.3		)
Additions (reductions) related to foreign exchange rates	(1.4		)	0.2			0.4
Balance, as of December 31,	$	26.9		$	26.8		$	32.4

Included in the balance of unrecognized tax benefits at December 31, 2015, 2016 and 2017, are $25.3 million, $26.0 million and $32.4 million, respectively, of tax benefits that, if recognized, would favorably affect the Company’s effective tax rate.

The Company records accrued interest and penalties, if any, related to unrecognized tax benefits in Income tax expense. The Company had $1.8 million, $1.4 million and $1.7 million in interest related to unrecognized tax benefits accrued at December 31, 2015, 2016 and 2017, respectively, which are included in the table above. For the years ended December 31, 2015, 2016 and 2017, no significant interest or penalties were recorded in Income tax expense.

The Company is subject to U.S. federal, state and local and foreign income tax in multiple jurisdictions. The Company is also periodically subject to tax examinations in these jurisdictions. The completion of examinations may result in the payment of additional taxes and/or the recognition of tax benefits. The Company is generally no longer subject to income tax examinations by U.S. federal, state and local or foreign taxing authorities for periods prior to 2011.

The Company does not expect any significant changes to its liability for tax benefits during the next 12 months.

Earnings Per Share

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Earnings Per Share

The calculation of basic earnings per share is based on the weighted average number of shares of the Company’s common stock outstanding during the period. Diluted earnings per share is similar to basic earnings per share, 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 Years Ended December 31,
	2015		2016		2017
Numerator
Net income (controlling interest)	$	509.5	$	472.8	$	689.5
Interest expense on convertible securities, net of taxes	15.3		15.5		15.5
Net income (controlling interest), as adjusted	$	524.8	$	488.3	$	705.0
Denominator
Average shares outstanding (basic)	54.3		54.2		56.0
Effect of dilutive instruments:
Stock options and restricted stock units	0.7		0.6		0.4
Junior convertible securities	2.2		2.2		2.2
Average shares outstanding (diluted)	57.2		57.0		58.6

Average shares outstanding (diluted) in the table above exclude share awards that have not satisfied performance conditions and the anti-dilutive effect of the following shares:



	For the Years Ended December 31,
	2015	2016	2017
Stock options and restricted stock units	0.0	0.6	0.1

The Company may settle portions of its Affiliate equity purchases in shares of its common stock. Because it is the Company’s intent to settle these potential purchases in cash, the calculation of diluted earnings per share excludes any potential dilutive effect from possible share settlements of Affiliate equity purchases.

Comprehensive Income

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Comprehensive Income

The following tables show the tax effects allocated to each component of Other comprehensive income (loss):



	For the Year Ended December 31, 2015
	Pre-Tax			Tax Benefit (Expense)			Net of Tax
Foreign currency translation adjustment	$	(93.2	)	$	—		$	(93.2	)
Change in net realized and unrealized gain (loss) on derivative securities	2.3			(0.4		)	1.9
Change in net unrealized gain (loss) on investment securities	34.8			(12.7		)	22.1
Other comprehensive income (loss)	$	(56.1	)	$	(13.1	)	$	(69.2	)



	For the Year Ended December 31, 2016
	Pre-Tax			Tax Benefit (Expense)			Net of Tax
Foreign currency translation adjustment	$	(115.3	)	$	—		$	(115.3	)
Change in net realized and unrealized gain (loss) on derivative securities	0.3			(0.2		)	0.1
Change in net unrealized gain (loss) on investment securities	(58.3		)	23.1			(35.2		)
Other comprehensive income (loss)	$	(173.3	)	$	22.9		$	(150.4	)



	For the Year Ended December 31, 2017
	Pre-Tax			Tax Benefit (Expense)			Net of Tax
Foreign currency translation adjustment	$	128.0		$	—		$	128.0
Change in net realized and unrealized gain (loss) on derivative securities	(0.7		)	(0.1		)	(0.8		)
Change in net unrealized gain (loss) on investment securities	(15.0		)	7.3			(7.7		)
Other comprehensive income (loss)	$	112.3		$	7.2		$	119.5

The components of accumulated other comprehensive income (loss), net of taxes, were as follows:



	Foreign Currency Translation Adjustment			Realized and Unrealized Gains (Losses) on Derivative Securities			Unrealized Gains (Losses) on Investment Securities ⁽¹⁾			Total
Balance, as of December 31, 2015	$	(98.6	)	$	0.3		$	45.0		$	(53.3	)
Other comprehensive gain (loss) before reclassifications	(115.3		)	(1.0		)	(22.5		)	(138.8		)
Amounts reclassified	—			1.1			(12.7		)	(11.6		)
Net other comprehensive gain (loss)	(115.3		)	0.1			(35.2		)	(150.4		)
Balance, as of December 31, 2016	$	(213.9	)	$	0.4		$	9.8		$	(203.7	)
Other comprehensive gain (loss) before reclassifications	128.0			(1.6		)	15.7			142.1
Amounts reclassified	—			0.8			(23.4		)	(22.6		)
Net other comprehensive gain (loss)	128.0			(0.8		)	(7.7		)	119.5
Balance, as of December 31, 2017	$	(85.9	)	$	(0.4	)	$	2.1		$	(84.2	)

__________________________


⁽¹⁾	See Note 2 for amounts reclassified from Other comprehensive income (loss).

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2017

Selected Quarterly Financial Data (Unaudited)

The following is a summary of the quarterly results of operations of the Company for the years ended December 31, 2016 and 2017:



	2016
	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
Revenue	$	545.4	$	554.1	$	544.7	$	550.3
Operating income	246.8		247.0		238.5		301.9
Income before income taxes	230.5		235.9		226.2		281.9
Net income (controlling interest)	104.0		108.3		110.2		150.2
Earnings per share (diluted)	$	1.90	$	1.98	$	2.02	$	2.67



	2017
	First Quarter		Second Quarter		Third Quarter		Fourth Quarter⁽¹⁾
Revenue	$	544.3	$	570.9	$	585.7	$	604.1
Operating income	262.5		275.9		289.5		280.0
Income before income taxes	253.3		266.9		282.9		264.0
Net income (controlling interest)	122.5		126.3		125.4		315.4
Earnings per share (diluted)	$	2.13	$	2.22	$	2.22	$	5.50

__________________________


⁽¹⁾	In the fourth quarter of 2017, the Company recorded a provisional one-time net benefit from changes in U.S tax laws (see Note 22) and an expense associated with the impairment of one of its Affiliates accounted for under the equity method (see Note 13).

Segment and Geographic Information

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Segment and Geographic Information

In the first quarter of 2017, the Company’s Chief Operating Decision Maker (the “CODM”) changed the manner in which he assesses the Company’s performance. In 2016, the CODM assessed the performance of the Company in three business segments representing three distribution channels. Given an increase in the number of the Company’s Affiliates accounted for under the equity method of accounting and changes in the way investment management services are delivered, during the first quarter of 2017, the CODM began to assess the performance of the Company as a single global active asset management company. As a result, the CODM now reviews information organized around one operating segment to evaluate and manage the Company’s business operations. Therefore, in the first quarter of 2017, the Company determined that it has one reportable segment. Prior period segment disclosures have been updated accordingly. In connection with this change, the Company completed impairment assessments based on its former three distribution channels, as well as its single global active asset management reporting unit, and determined that there were no impairments under either approach.

The following table presents Revenue and Fixed assets (net) of the Company by geographic location. Revenue by geographic location is primarily based on the location of an Affiliate.



	For the Years Ended December 31,
	2015		2016		2017
Revenue
United States	$	1,657.2	$	1,477.5	$	1,571.4
United Kingdom	645.3		566.4		587.3
Other	182.0		150.7		146.3
Total	$	2,484.5	$	2,194.6	$	2,305.0



	December 31,
	2015		2016		2017
Fixed Assets, Net
United States	$	98.6	$	97.3	$	97.8
United Kingdom	12.3		9.9		11.4
Other	3.2		2.9		1.8
Total	$	114.1	$	110.1	$	111.0

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company’s Board of Directors authorized a share repurchase program in January 2018 authorizing the Company to repurchase up to 3.4 million shares of its common stock, and this authorization has no expiry. As of the January 2018 authorization, there were a total of 5.0 million shares remaining available for repurchase under the Company’s repurchase programs. As of February 21, 2018, the Company had repurchased 0.7 million shares of common stock, at an average share price of $193.18

Schedule II Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2017

Valuation and Qualifying Accounts [Abstract]

Schedule II Valuation and Qualifying Accounts

Schedule II

Valuation and Qualifying Accounts



(in millions)	Balance Beginning of Period		Additions Charged to Costs and Expenses		Additions Charged to Other Accounts		Deductions		Balance End of Period
Income Tax Valuation Allowance
Year Ending December 31,
2017	$	22.1	$	1.1	$	0.9	$	—	$	24.1
2016	20.5		1.3		0.3		—		22.1
2015	18.4		2.1		—		—		20.5

Other Allowances⁽¹⁾
Year Ending December 31,
2017	$	10.3	$	0.6	$	—	$	7.3	$	3.6
2016	10.6		5.0		—		5.3		10.3
2015	12.1		0.7		—		2.2		10.6

__________________________


⁽¹⁾	Other Allowances represented reserves on notes received in connection with transfers of our interests in certain Affiliates, as well as other receivable amounts, which we considered uncollectible. Deductions represent the reversal of such reserves upon collection of the amounts due.

Business and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Basis of Presentation

Basis of Presentation and Use of Estimates

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.

Principles of Consolidation

Investments in Affiliates

Affiliate Sponsored Investment Vehicles

Cash and Cash Equivalents

Receivables

Investments in Marketable Securities

Fair Value Measurements

Level 1 - Unadjusted quoted market prices for identical instruments in active markets;

Fixed Assets

Leases

Acquired Client Relationships and Goodwill

Issuance Costs

Derivative Financial Instruments

Contingent Payment Arrangements

Income Taxes

Foreign Currency Translation

Concentration of Credit Risk

Revenue Recognition

Earnings Per Share

Share-Based Compensation Plans

Recent Accounting Developments

Fair Value of Financial Instruments

The following are descriptions of the significant financial assets and liabilities measured at fair value and the fair value methodologies used.

Foreign currency forward contracts use model-derived valuations in which all significant inputs are observable in active markets to determine fair value.

It is the Company’s policy to value financial assets or liabilities transferred as of the beginning of the period in which the transfer occurs.

Investments in Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2017

Marketable Securities [Abstract]

Schedule of Cost, Gross Unrealized Gains and Losses, and Fair Value of Investments

The following is a summary of the cost, gross unrealized gains and losses and fair value of investments classified as available-for-sale and trading:



	Available-for-Sale						Trading
	December 31, 2016			December 31, 2017			December 31, 2016			December 31, 2017
Cost	$	66.1		$	18.3		$	34.4		$	48.8
Unrealized Gains	17.6			2.7			6.6			10.3
Unrealized Losses	(1.8		)	(0.4		)	(0.5		)	(1.9		)
Fair Value	$	81.9		$	20.6		$	40.5		$	57.2

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

Schedule of Net Assets and Liabilities and Maximum Risk of Losses Related to Unconsolidated VIEs

Investments in Affiliates and Affiliate Sponsored Investment Products (Tables)

12 Months Ended

Dec. 31, 2017

Variable Interest Entities

The net assets of Affiliate sponsored investment products that were considered VIEs accounted for under the equity method and the Company’s maximum risk of loss were as follows:



	December 31, 2016				December 31, 2017
	Unconsolidated VIE Net Assets		Carrying Value and Maximum Risk of Loss		Unconsolidated VIE Net Assets		Carrying Value and Maximum Risk of Loss
Affiliate sponsored investment products	$	1,756.6	$	9.4	$	2,154.6	$	10.2



	December 31, 2016				December 31, 2017
	Unconsolidated VIE Net Assets		Carrying Value and Maximum Exposure to Loss		Unconsolidated VIE Net Assets		Carrying Value and Maximum Exposure to Loss
Affiliates accounted for under the equity method	$	1,047.6	$	2,846.8	$	1,594.4	$	2,765.7

Tabular disclosure of the significant judgments and assumptions made in determining whether a variable interest (as defined) held by the entity requires the variable interest entity (VIE) (as defined) to be consolidated and (or) disclose information about its involvement with the VIE, individually or in aggregate (as applicable); the nature of restrictions, if any, on the consolidated VIE's assets and on the settlement of its liabilities reported by an entity in its statement of financial position, including the carrying amounts of such assets and liabilities; the nature of, and changes in, the risks associated with involvement in the VIE; how involvement with the VIE affects the entity's financial position, financial performance, and cash flows; the lack of recourse if creditors (or beneficial interest holders) of the consolidated VIE have no recourse to the general credit of the primary beneficiary (if applicable); the terms of arrangements, giving consideration to both explicit arrangements and implicit variable interests, if any, that could require the entity to provide financial support to the VIE, including events or circumstances that could expose the entity to a loss; the methodology used by the entity for determining whether or not it is the primary beneficiary of the variable interest entity; the significant factors considered and judgments made in determining that the power to direct the activities of a VIE that most significantly impact the VIE's economic performance are shared (as defined); the carrying amounts and classification of assets and liabilities of the VIE included in the statement of financial position; the entity's maximum exposure to loss, if any, as a result of its involvement with the VIE, including how the maximum exposure is determined and significant sources of the entity's exposure to the VIE; a comparison of the carrying amounts of the assets and liabilities and the entity's maximum exposure to loss; information about any liquidity arrangements, guarantees, and (or) other commitments by third parties that may affect the fair value or risk of the entity's variable interest in the VIE; whether or not the entity has provided financial support or other support (explicitly or implicitly) to the VIE that it was not previously contractually required to provide or whether the entity intends to provide that support, including the type and amount of the support and the primary reasons for providing the support; and supplemental information the entity determines necessary to provide.

Senior Notes (Tables)

12 Months Ended

Dec. 31, 2017

Schedule of Principal Terms of Senior Notes Outstanding

At December 31, 2017, the Company had two senior notes outstanding and their respective principal terms are summarized in the following table:



	2024 Senior Notes			2025 Senior Notes
Issue date	February 2014			February 2015
Maturity date	February 2024			August 2025
Potential Call Date⁽¹⁾	Any Time			Any Time
Par value (in millions)	$	400.0		$	350.0
Call Price⁽¹⁾	As Defined			As Defined
Stated coupon	4.25		%	3.50		%
Coupon frequency	Semi-annually			Semi-annually

__________________________


⁽¹⁾	The senior notes may be redeemed at any time, in whole or in part, at a make-whole redemption price plus accrued and unpaid interest.

Convertible Securities (Tables)

12 Months Ended

Dec. 31, 2017

Schedule of Carrying Value of Convertible Securities

The carrying value and principal amount at maturity of the junior convertible securities were as follows:



	December 31, 2016				December 31, 2017
	Carrying Value		Principal Amount at Maturity		Carrying Value		Principal Amount at Maturity
Junior convertible securities⁽¹⁾	$	307.5	$	430.8	$	309.9	$	430.8

__________________________


⁽¹⁾	The carrying value is accreted to the principal amount at maturity over a remaining life of 20 years.

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Schedule of Fair Value of Financial 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, 2016		Fair Value Measurements
	December 31, 2016		Level 1		Level 2		Level 3
Financial Assets
Cash equivalents	$	64.1	$	64.1	$	—	$	—
Investments in marketable securities⁽¹⁾
Trading securities	40.5		40.5		—		—
Available-for-sale securities	81.9		81.9		—		—
Other investments	3.4		3.4		—		—
Foreign currency forward contracts⁽²⁾	0.6		—		0.6		—
Financial Liabilities⁽²⁾
Contingent payment arrangements	$	8.6	$	—	$	—	$	8.6
Affiliate equity obligations	12.1		—		—		12.1
Foreign currency forward contracts	0.5		—		0.5		—



			Fair Value Measurements
	December 31, 2017		Fair Value Measurements
	December 31, 2017		Level 1		Level 2		Level 3
Financial Assets
Cash equivalents	$	40.4	$	40.4	$	—	$	—
Investments in marketable securities⁽¹⁾
Trading securities	57.2		57.2		—		—
Available-for-sale securities	20.6		20.6		—		—
Foreign currency forward contracts⁽²⁾	0.2		—		0.2		—
Financial Liabilities⁽²⁾
Contingent payment arrangements	$	9.4	$	—	$	—	$	9.4
Affiliate equity obligations	49.2		—		—		49.2
Foreign currency forward contracts	0.6		—		0.6		—

__________________________


⁽¹⁾	Principally investments in equity securities.

⁽²⁾Amounts are presented within Other assets or Other liabilities.

Schedule of Changes in Level 3 Financial Assets and Liabilities

The following tables present the changes in level 3 liabilities:



	For the Years Ended December 31,
	2016						2017
	Contingent Payment Arrangements			Affiliate Equity Obligations			Contingent Payment Arrangements			Affiliate Equity Obligations
Balance, beginning of period	$	10.2		$	62.3		$	8.6		$	12.1
Net realized and unrealized (gains) losses⁽¹⁾	(1.6		)	3.1			7.6			5.5
Purchases and issuances⁽²⁾	—			69.1			—			206.1
Settlements and reductions	—			(122.4		)	(6.8		)	(174.5		)
Balance, end of period	$	8.6		$	12.1		$	9.4		$	49.2

Net change in unrealized (gains) losses relating to instruments still held at the reporting date	$	(1.6	)	$	—		$	2.8		$	—

__________________________


⁽¹⁾	Accretion and changes in the expected value of the Company’s contingent payment arrangements and Affiliate equity obligations are recorded in Imputed interest expense and contingent payment arrangements.


⁽²⁾	Includes transfers from Redeemable non-controlling interests and other activity.

Schedule of Quantitative Information

The following table presents certain quantitative information about the significant unobservable inputs used in valuing the Company’s level 3 financial liabilities:



	Quantitative Information about Level 3 Fair Value Measurements
	Valuation Techniques	Unobservable Input	Fair Value at December 31, 2016		Range at December 31, 2016	Fair Value at December 31, 2017		Range at December 31, 2017
Contingent payment arrangements	Discounted cash flow	Growth rates	$	8.6	3% - 8%	$	9.4	7% - 8%
		Discount rates			14% - 15%			15% - 16%
Affiliate equity obligations	Discounted cash flow	Growth rates	12.1		4% - 10%	49.2		0% - 11%
		Discount rates			15% - 16%			12% - 16%

Schedule of Investments

The following table summarizes the nature of the Company’s investments, unfunded commitments and any related liquidity restrictions or other factors that may impact the ultimate value realized:



	December 31, 2016				December 31, 2017
Category of Investment	Fair Value		Unfunded Commitments		Fair Value		Unfunded Commitments
Private equity⁽¹⁾	$	137.8	$	92.2	$	156.1	$	98.8
Other funds⁽²⁾	9.7		—		8.9		—
Other investments⁽³⁾	$	147.5	$	92.2	$	165.0	$	98.8

__________________________


⁽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 $59.9 million and $80.1 million as of December 31, 2016 and 2017, respectively.

Schedule of Financial Liabilities not Carried at Fair Value

The following table summarizes the Company’s other financial liabilities not carried at fair value:



	December 31, 2016				December 31, 2017
	Carrying Value		Fair Value		Carrying Value		Fair Value		Fair Value Hierarchy
Senior notes	$	945.1	$	936.0	$	745.7	$	765.2	Level 2
Convertible securities	307.5		466.9		309.9		549.8		Level 2

Goodwill and Acquired Client Relationships (Tables)

12 Months Ended

Dec. 31, 2017

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
	2016			2017
Balance, as of January 1,	$	2,668.4		$	2,628.1
Foreign currency translation	(40.3		)	34.4
Balance, as of December 31,	$	2,628.1		$	2,662.5

Schedule of Changes in, and 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, 2015	$	1,301.8		$	(680.4	)	$	621.4		$	1,065.0		$	1,686.4
Intangible amortization and impairments	—			(107.7		)	(107.7		)	(2.5		)	(110.2		)
Foreign currency translation	(11.8		)	—			(11.8		)	(67.0		)	(78.8		)
Balance, as of December 31, 2016	$	1,290.0		$	(788.1	)	$	501.9		$	995.5		$	1,497.4
Intangible amortization and impairments	—			(86.4		)	(86.4		)	—			(86.4		)
Foreign currency translation	5.5			—			5.5			33.2			38.7
Balance, as of December 31, 2017	$	1,295.5		$	(874.5	)	$	421.0		$	1,028.7		$	1,449.7

Equity Method Investments in Affiliates (Tables)

12 Months Ended

Dec. 31, 2017

Equity Method Investments and Joint Ventures [Abstract]

Schedule of Aggregate Purchase Price Allocation for Investments

The purchase price allocation for the 2016 investments was as follows:



	Total
Definite-lived acquired client relationships⁽¹⁾	$	560.8
Indefinite-lived acquired client relationships	36.9
Tangible assets	2.0
Deferred tax liability	(91.8		)
Goodwill	854.4
Consideration paid	$	1,362.3

__________________________


⁽¹⁾	The expected period of economic benefit utilized in the purchase price allocation for these definite-lived acquired client relationships was 15 years.

Schedule of Changes in Equity Method Investments in Affiliates

The following table presents the change in Equity method investments in Affiliates:



	2016			2017
Balance, January 1,	$	1,937.1		3,368.3
Equity method earnings	388.0			501.4
Equity method intangible amortization and impairments	(59.2		)	(199.2		)
Distributions of earnings from equity method investments	(346.4		)	(429.8		)
Investments	1,361.3			29.8
Foreign currency translation	8.0			62.3
Other⁽¹⁾	79.5			(28.1		)
Balance, December 31,	$	3,368.3		$	3,304.7

__________________________


⁽¹⁾	Primarily reflects deferred income taxes recorded on new investments.

The following table presents summarized financial information for Affiliates accounted for under the equity method:



	For the Years Ended December 31,
	2015⁽²⁾		2016⁽²⁾		2017
Revenue⁽¹⁾	$	2,217.1	$	2,200.9	$	3,126.3
Net income⁽¹⁾	431.5		1,068.9		2,182.7



	December 31,
	2016		2017
Assets	$	1,915.3	$	3,324.9
Liabilities and Non-controlling interests	862.4		1,405.5

__________________________


⁽¹⁾	Revenue and the associated Net income include asset and performance based fees and the impact of consolidated investment products.


⁽²⁾	Revenue and Net income reflect investments in new Affiliates for the full-year, regardless of the date of the Company’s investment.

Schedule of Financial Information for Affiliates Accounted for Under the Equity Method

The following table presents the change in Equity method investments in Affiliates:



	2016			2017
Balance, January 1,	$	1,937.1		3,368.3
Equity method earnings	388.0			501.4
Equity method intangible amortization and impairments	(59.2		)	(199.2		)
Distributions of earnings from equity method investments	(346.4		)	(429.8		)
Investments	1,361.3			29.8
Foreign currency translation	8.0			62.3
Other⁽¹⁾	79.5			(28.1		)
Balance, December 31,	$	3,368.3		$	3,304.7

__________________________


⁽¹⁾	Primarily reflects deferred income taxes recorded on new investments.

The following table presents summarized financial information for Affiliates accounted for under the equity method:



	For the Years Ended December 31,
	2015⁽²⁾		2016⁽²⁾		2017
Revenue⁽¹⁾	$	2,217.1	$	2,200.9	$	3,126.3
Net income⁽¹⁾	431.5		1,068.9		2,182.7



	December 31,
	2016		2017
Assets	$	1,915.3	$	3,324.9
Liabilities and Non-controlling interests	862.4		1,405.5

__________________________


⁽¹⁾	Revenue and the associated Net income include asset and performance based fees and the impact of consolidated investment products.


⁽²⁾	Revenue and Net income reflect investments in new Affiliates for the full-year, regardless of the date of the Company’s investment.

Fixed Assets and Lease Commitments (Tables)

12 Months Ended

Dec. 31, 2017

Fixed Assets and Lease Commitments [Abstract]

Schedule of Fixed Assets

Fixed assets consisted of the following:



	December 31,
	2016			2017
Building and leasehold improvements	$	103.5		$	111.9
Software	52.5			50.8
Equipment	39.5			44.5
Furniture and fixtures	20.8			21.4
Land, improvements and other	17.9			18.7
Fixed assets, at cost	234.2			247.3
Accumulated depreciation and amortization	(124.1		)	(136.3		)
Fixed assets, net	$	110.1		$	111.0

Schedule of Aggregate Future Minimum Payments for Operating Leases

At December 31, 2017, the Company’s aggregate future minimum payments for operating leases having initial or non-cancelable lease terms greater than one year were payable as follows:



Year	Required Minimum Payments
2018	$	37.0
2019	33.9
2020	35.3
2021	33.6
2022	26.6
Thereafter	89.9

Payables and Accrued Liabilities (Tables)

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Schedule of Accounts Payable and Accrued Liabilities

Payables and accrued liabilities consisted of the following:



	December 31,
	2016		2017
Accrued compensation	$	418.5	$	472.5
Unsettled fund share payables	83.2		103.1
Accrued income taxes	87.7		93.0
Accrued share repurchases	—		23.1
Accrued professional fees	26.1		22.5
Other	113.8		93.0
Payables and accrued liabilities	$	729.3	$	807.2

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2017

Schedule of Recent Share Repurchase Activity

The following is a summary of the Company’s share repurchase activity for the years ended December 31, 2015, 2016 and 2017:



Year	Shares Repurchased	Average Price
2015	1.7	$	209.39
2016	0.2	161.16
2017	2.4	173.19

Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Recent Share-Based Compensation Expense

The following is a summary of share-based compensation expense for the years ended December 31, 2015, 2016 and 2017:



Year	Share-Based Compensation Expense		Tax Benefit
2015	$	34.2	$	13.2
2016	39.2		15.1
2017	40.4		13.6

Schedule of Transactions of the Company's Stock Options

The following table summarizes the transactions of the Company’s stock options:



	Stock Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)
Unexercised options outstanding—January 1, 2017	1.4		$	108.53
Options granted	0.0		168.60
Options exercised	(0.7	)	97.54
Options forfeited	(0.1	)	140.26
Unexercised options outstanding—December 31, 2017	0.6		122.04		3.9
Exercisable at December 31, 2017	0.2		115.74		1.7

Schedule of Assumptions Used to Determine Fair Value of Options Granted



	For the Years Ended December 31,
	2015		2016		2017
Dividend yield	0.0	%	0.0	%	0.5	%
Expected volatility⁽¹⁾	26.7	%	30.7	%	28.0	%
Risk-free interest rate⁽²⁾	1.5	%	1.6	%	2.1	%
Expected life of options (in years)⁽³⁾	5.0		5.7		5.7
Forfeiture rate	0.0	%	0.0	%	0.0	%

__________________________


⁽¹⁾	Expected volatility is based on historical and implied volatility.


⁽²⁾	Risk-free interest rate is based on the U.S. Treasury yield curve in effect at the date of grant.


⁽³⁾	Expected life of options (in years) is based on the Company’s historical and expected exercise behavior.

Schedule of Transactions of the Company's Restricted Stock

The following table summarizes the transactions of the Company’s restricted stock:



	Restricted Stock		Weighted Average Grant Date Value
Unvested units—January 1, 2017	0.6		$	168.84
Units granted	0.2		152.99
Units vested	(0.4	)	166.22
Units forfeited	(0.0	)	170.39
Unvested units—December 31, 2017	0.4		162.32

Redeemable Non-Controlling Interests (Tables)

12 Months Ended

Dec. 31, 2017

Noncontrolling Interest [Abstract]

Schedule of Changes in Redeemable Non-Controlling Interests

The following table presents the changes in Redeemable non-controlling interests:



	December 31,
	2016			2017
Balance, as of January 1,	$	612.5		$	673.5
Changes attributable to consolidated products	16.1			12.4
Transfers to Other liabilities	(69.1		)	(192.3		)
Transfers from non-controlling interests	42.6			76.8
Changes in redemption value	71.4			241.5
Balance, as of December 31,	$	673.5		$	811.9

Affiliate Equity (Tables)

12 Months Ended

Dec. 31, 2017

Affiliate Equity

Schedule of Affiliate Equity Expense

The following is a summary of Affiliate equity expense:



	For the Years Ended December 31,
	2015		2016		2017
Controlling interest	$	16.9	$	10.0	$	13.2
Non-controlling interest	51.6		31.2		36.8
Total	$	68.5	$	41.2	$	50.0

Schedule of Affiliate Equity Unrecognized Expense

The following is a summary of unrecognized Affiliate equity expense for the years ended December 31, 2015, 2016 and 2017:



	Unrecognized Affiliate Equity Expense
Year	Controlling Interest		Remaining Life	Non-Controlling Interest		Remaining Life
2015	$	22.4	3 years	$	51.9	5 years
2016	31.3		4 years	70.7		5 years
2017	33.3		5 years	95.9		6 years

Schedule of the Effect of Changes in the Company's Ownership Interest in its Affiliates on the Controlling Interest's Equity



	For the Years Ended December 31,
	2015			2016			2017
Net income (controlling interest)	$	509.5		$	472.8		$	689.5
Increase / (decrease) in controlling interest paid-in capital from purchases and sales of Affiliate equity issuances	0.9			1.6			(1.0		)
Decrease in controlling interest paid-in capital related to Affiliate equity repurchases	(87.6		)	(38.0		)	(116.2		)
Net income attributable to controlling interest and transfers from non-controlling interests	$	422.8		$	436.4		$	572.3

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of Income Tax Provision Attributable to Controlling and Non-Controlling Interests

The following table presents our consolidated provision for income taxes:



	For the Years Ended December 31,
	2015			2016			2017
Controlling interests:
Current tax	$	152.4		$	168.1		$	173.8
Intangible-related deferred taxes	77.7			84.3			(98.5		)
Other deferred taxes	27.7			(23.2		)	(24.9		)
Total controlling interests	257.8			229.2			50.4
Non-controlling interests:
Current tax	$	9.8		$	8.2		$	8.2
Deferred taxes	(4.2		)	(1.8		)	(0.2		)
Total non-controlling interests	5.6			6.4			8.0
Provision for income taxes	$	263.4		$	235.6		$	58.4
Income before income taxes (controlling interest)	$	767.3		$	702.0		$	739.9
Effective tax rate attributable to controlling interests⁽¹⁾	33.6		%	32.6		%	6.8		%

__________________________


⁽¹⁾	Taxes attributable to the controlling interest divided by Income before income taxes (controlling interest).

Schedule of Consolidated Provision for Income Taxes

The consolidated provision for income taxes consisted of the following:



	For the Years Ended December 31,
	2015			2016			2017
Current:
Federal	$	106.3		$	103.4		$	109.0
State	18.3			22.9			18.9
Foreign	37.6			50.0			54.1
Total current	162.2			176.3			182.0
Deferred:
Federal	103.8			62.3			(124.9		)
State	14.8			10.0			10.4
Foreign	(17.4		)	(13.0		)	(9.1		)
Total deferred	101.2			59.3			(123.6		)
Provision for income taxes	$	263.4		$	235.6		$	58.4

Schedule of Components of Income before Income Taxes

For financial reporting purposes, Income before income taxes consisted of the following:



	For the Years Ended December 31,
	2015		2016		2017
Domestic	$	827.6	$	688.1	$	756.5
International	263.0		286.5		310.6
	$	1,090.6	$	974.6	$	1,067.1

Schedule of Effective Income Tax Rate Computed Using Income before Income Taxes and Applying U.S. Federal Income Tax Rate

The following table reconciles the U.S. federal statutory tax rate to the Company’s effective tax rate:



	For the Years Ended December 31,
	2015		2016		2017
Statutory U.S. federal tax rate	35.0	%	35.0	%	35.0	%
State income taxes, net of federal benefit	2.6		2.9		2.7
Effect of foreign operations	(3.5	)	(4.6	)	(5.4	)
Equity compensation	0.8		(0.4	)	(0.7	)
Effect of changes in tax law, rates	(0.8	)	(0.3	)	(25.2	)
Other	(0.5	)	—		0.4
Effective tax rate (controlling interest)	33.6	%	32.6	%	6.8	%
Effect of income from non-controlling interests	(9.2	)	(8.4	)	(1.3	)
Effective tax rate	24.4	%	24.2	%	5.5	%

Schedule of Components of Deferred Tax Assets and Liabilities

The significant components of the Company’s Deferred income tax liability (net) are as follows:



	December 31,
	2016			2017
Deferred Tax Assets
State net operating loss carryforwards	$	17.4		$	16.8
Foreign loss carryforwards	14.6			16.3
Tax benefit of uncertain tax positions	12.1			11.4
Deferred compensation	34.1			10.4
Foreign tax credits	10.0			—
Accrued expenses	3.9			1.3
Total deferred tax assets	92.1			56.2
Valuation allowance	(22.1		)	(24.1		)
Deferred tax assets, net of valuation allowance	$	70.0		$	32.1
Deferred Tax Liabilities
Intangible asset amortization	$	(396.8	)	$	(258.6	)
Non-deductible intangible amortization	(177.0		)	(150.8		)
Convertible securities interest	(109.0		)	(77.9		)
Deferred income	(47.2		)	(5.9		)
Other	(0.8		)	(6.3		)
Total deferred tax liabilities	(730.8		)	(499.5		)
Deferred income tax liability (net)	$	(660.8	)	$	(467.4	)

Schedule of Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits

A reconciliation of the changes in unrecognized tax benefits is as follows:



	For the Years Ended December 31,
	2015			2016			2017
Balance, as of January 1,	$	28.8		$	26.9		$	26.8
Additions based on current year tax positions	2.2			3.8			6.0
Additions based on prior years’ tax positions	1.6			0.6			1.5
Reductions related to lapses of statutes of limitations	(4.3		)	(4.7		)	(2.3		)
Additions (reductions) related to foreign exchange rates	(1.4		)	0.2			0.4
Balance, as of December 31,	$	26.9		$	26.8		$	32.4

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Schedule of Reconciliation of the Numerator and Denominator used in the Calculation 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 Years Ended December 31,
	2015		2016		2017
Numerator
Net income (controlling interest)	$	509.5	$	472.8	$	689.5
Interest expense on convertible securities, net of taxes	15.3		15.5		15.5
Net income (controlling interest), as adjusted	$	524.8	$	488.3	$	705.0
Denominator
Average shares outstanding (basic)	54.3		54.2		56.0
Effect of dilutive instruments:
Stock options and restricted stock units	0.7		0.6		0.4
Junior convertible securities	2.2		2.2		2.2
Average shares outstanding (diluted)	57.2		57.0		58.6

Schedule of Diluted Earnings per Share Calculations, Excluding the Anti-dilutive Effect of Shares

Average shares outstanding (diluted) in the table above exclude share awards that have not satisfied performance conditions and the anti-dilutive effect of the following shares:



	For the Years Ended December 31,
	2015	2016	2017
Stock options and restricted stock units	0.0	0.6	0.1

Comprehensive Income (Tables)

12 Months Ended

Dec. 31, 2017

Schedule of Tax Effects Allocated to each Component of Other Comprehensive Income

The following tables show the tax effects allocated to each component of Other comprehensive income (loss):



	For the Year Ended December 31, 2015
	Pre-Tax			Tax Benefit (Expense)			Net of Tax
Foreign currency translation adjustment	$	(93.2	)	$	—		$	(93.2	)
Change in net realized and unrealized gain (loss) on derivative securities	2.3			(0.4		)	1.9
Change in net unrealized gain (loss) on investment securities	34.8			(12.7		)	22.1
Other comprehensive income (loss)	$	(56.1	)	$	(13.1	)	$	(69.2	)



	For the Year Ended December 31, 2016
	Pre-Tax			Tax Benefit (Expense)			Net of Tax
Foreign currency translation adjustment	$	(115.3	)	$	—		$	(115.3	)
Change in net realized and unrealized gain (loss) on derivative securities	0.3			(0.2		)	0.1
Change in net unrealized gain (loss) on investment securities	(58.3		)	23.1			(35.2		)
Other comprehensive income (loss)	$	(173.3	)	$	22.9		$	(150.4	)



	For the Year Ended December 31, 2017
	Pre-Tax			Tax Benefit (Expense)			Net of Tax
Foreign currency translation adjustment	$	128.0		$	—		$	128.0
Change in net realized and unrealized gain (loss) on derivative securities	(0.7		)	(0.1		)	(0.8		)
Change in net unrealized gain (loss) on investment securities	(15.0		)	7.3			(7.7		)
Other comprehensive income (loss)	$	112.3		$	7.2		$	119.5

Schedule of Components of Accumulated Other Comprehensive Income, Net of Taxes

The components of accumulated other comprehensive income (loss), net of taxes, were as follows:



	Foreign Currency Translation Adjustment			Realized and Unrealized Gains (Losses) on Derivative Securities			Unrealized Gains (Losses) on Investment Securities ⁽¹⁾			Total
Balance, as of December 31, 2015	$	(98.6	)	$	0.3		$	45.0		$	(53.3	)
Other comprehensive gain (loss) before reclassifications	(115.3		)	(1.0		)	(22.5		)	(138.8		)
Amounts reclassified	—			1.1			(12.7		)	(11.6		)
Net other comprehensive gain (loss)	(115.3		)	0.1			(35.2		)	(150.4		)
Balance, as of December 31, 2016	$	(213.9	)	$	0.4		$	9.8		$	(203.7	)
Other comprehensive gain (loss) before reclassifications	128.0			(1.6		)	15.7			142.1
Amounts reclassified	—			0.8			(23.4		)	(22.6		)
Net other comprehensive gain (loss)	128.0			(0.8		)	(7.7		)	119.5
Balance, as of December 31, 2017	$	(85.9	)	$	(0.4	)	$	2.1		$	(84.2	)

__________________________


⁽¹⁾	See Note 2 for amounts reclassified from Other comprehensive income (loss).

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Results of Operations

The following is a summary of the quarterly results of operations of the Company for the years ended December 31, 2016 and 2017:



	2016
	First Quarter		Second Quarter		Third Quarter		Fourth Quarter
Revenue	$	545.4	$	554.1	$	544.7	$	550.3
Operating income	246.8		247.0		238.5		301.9
Income before income taxes	230.5		235.9		226.2		281.9
Net income (controlling interest)	104.0		108.3		110.2		150.2
Earnings per share (diluted)	$	1.90	$	1.98	$	2.02	$	2.67



	2017
	First Quarter		Second Quarter		Third Quarter		Fourth Quarter⁽¹⁾
Revenue	$	544.3	$	570.9	$	585.7	$	604.1
Operating income	262.5		275.9		289.5		280.0
Income before income taxes	253.3		266.9		282.9		264.0
Net income (controlling interest)	122.5		126.3		125.4		315.4
Earnings per share (diluted)	$	2.13	$	2.22	$	2.22	$	5.50

__________________________


⁽¹⁾	In the fourth quarter of 2017, the Company recorded a provisional one-time net benefit from changes in U.S tax laws (see Note 22) and an expense associated with the impairment of one of its Affiliates accounted for under the equity method (see Note 13).

Segment and Geographic Information (Tables)

12 Months Ended

Dec. 31, 2017

Segment Reporting [Abstract]

Schedule of Revenue and Fixed Assets, net of the Company by Geographic Location

The following table presents Revenue and Fixed assets (net) of the Company by geographic location. Revenue by geographic location is primarily based on the location of an Affiliate.



	For the Years Ended December 31,
	2015		2016		2017
Revenue
United States	$	1,657.2	$	1,477.5	$	1,571.4
United Kingdom	645.3		566.4		587.3
Other	182.0		150.7		146.3
Total	$	2,484.5	$	2,194.6	$	2,305.0



	December 31,
	2015		2016		2017
Fixed Assets, Net
United States	$	98.6	$	97.3	$	97.8
United Kingdom	12.3		9.9		11.4
Other	3.2		2.9		1.8
Total	$	114.1	$	110.1	$	111.0

Business and Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2017
Equipment \| Minimum
Fixed Assets
Estimated useful lives of office equipment, furniture and fixtures	3 years
Equipment \| Maximum
Fixed Assets
Estimated useful lives of office equipment, furniture and fixtures	10 years
Computer software \| Minimum
Fixed Assets
Estimated useful lives of office equipment, furniture and fixtures	3 years
Computer software \| Maximum
Fixed Assets
Estimated useful lives of office equipment, furniture and fixtures	7 years

Investments in Marketable Securities - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cost of investments in marketable securities, gross unrealized gains and losses
Proceeds from sale of investment classified as available-for-sale	$ 82.3	$ 61.1
Realized net gains on available-for-sale securities	29.2	19.2
Proceeds from trading securities	29.9	82.8
Realized net gains on trading securities	$ 6.6	$ 1.0

Investments in Marketable Securities - Summary of the Cost, Gross Unrealized Gains and Losses, and Fair Value of Investments (Details) - Equity Securities - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Available-for-Sale
Cost	$ 18.3	$ 66.1
Unrealized Gains	2.7	17.6
Unrealized Losses	(0.4)	(1.8)
Fair Value	20.6	81.9
Trading
Cost	48.8	34.4
Unrealized Gains	10.3	6.6
Unrealized Losses	(1.9)	(0.5)
Fair Value	$ 57.2	$ 40.5

Investments in Affiliates and Affiliate Sponsored Investment Products - Affiliate Accounted For Under Equity Method (Details) - Affiliates accounted for under the equity method - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Unconsolidated VIE Net Assets	$ 1,594.4	$ 1,047.6
Carrying Value and Maximum Exposure to Loss	$ 2,765.7	$ 2,846.8

Investments in Affiliates and Affiliate Sponsored Investment Products - Affiliated Sponsored Investment Products (Details) - Affiliate sponsored investment products - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Unconsolidated VIE Net Assets	$ 2,154.6	$ 1,756.6
Carrying Value and Maximum Risk of Loss	$ 10.2	$ 9.4

Senior Bank Debt (Details) - USD ($) $ in Millions	12 Months Ended
Senior Bank Debt (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument
Term loan outstanding	$ 809.0	$ 868.6
Credit Facility
Debt Instrument
Maximum borrowing capacity	1,450.0
Maximum borrowing capacity, additional amount	350.0
Line of credit facility amount outstanding	$ 425.0	$ 485.0
Weighted average interest rate	2.76%	1.88%
Commitment fee amount	$ 1.5	$ 1.0
Term Loan Facility
Debt Instrument
Principal Amount at Maturity	385.0
Maximum borrowing capacity, additional amount	65.0
Term loan outstanding	$ 385.0	$ 385.0
Weighted average interest rate on amount outstanding	2.69%	1.87%

Senior Notes - Additional Information (Details)	12 Months Ended
Senior Notes - Additional Information (Details)	Dec. 31, 2017 USD ($) note
Debt Instrument
Number of senior notes outstanding \| note	2
2022 Senior Notes
Debt Instrument
Notes redeemed, canceled and retired \| $	$ 200,000,000.0
Stated interest rate	6.375%
Redemption price (as percentage)	100.00%

Senior Notes - Principal Terms of Senior Notes Outstanding (Details) - Senior Notes
$ in Millions

Dec. 31, 2017

USD ($)

^[1]

2024 Senior Notes

Debt Instrument

Par value (in millions)

$ 400.0

Stated coupon

4.25%

2025 Senior Notes

Debt Instrument

Par value (in millions)

$ 350.0

Stated coupon

3.50%

[1]	The senior notes may be redeemed at any time, in whole or in part, at a make-whole redemption price plus accrued and unpaid interest.

Convertible Securities - Carrying Value and Principal Amount of Junior Convertible Securities (Details) - Junior convertible securities - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Debt Instrument

Carrying Value

^[1]

$ 309.9

$ 307.5

Principal Amount at Maturity

$ 430.8

Debt instrument term

20 years

[1]	The carrying value is accreted to the principal amount at maturity over a remaining life of 20 years.

Convertible Securities - Additional Information (Details) - Junior Convertible Securities	12 Months Ended
	Dec. 31, 2017 USD ($) trading_day $ / shares
Debt Instrument
Stated interest rate	5.15%
Principal amount at maturity \| $	$ 50
Conversion ratio (in shares)	0.25
Conversion price (in usd per share) \| $ / shares	$ 200
Redemption closing price trigger (in usd per share) \| $ / shares	$ 260
Number of trading days closing price has exceeded threshold \| trading_day	20
Number of consecutive trading days \| trading_day	30
Deferred tax liability \| $	$ 7,200,000

Forward Equity and Equity Distribution Program (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock
Proceeds from issuance of common stock	$ 41,900,000	$ 465,800,000	$ 57,800,000
Common stock, shares outstanding (in shares)	58,500,000	58,500,000	55,800,000	55,800,000
Equity Distribution Program
Class of Stock
Stock program, maximum amount authorized	$ 500,000,000
Proceeds from issuance of common stock	$ 0	$ 440,300,000
Maximum number of shares available for sale under agreement (in shares)		2,900,000
Common stock price (in dollars per share)		$ 167.25
Number of common shares issued (in shares)		2,700,000
Number of shares net settled for cash (in shares)		200,000
Average share price of shares net settled for cash (in dollars per share)		$ 144.59
Common stock, shares outstanding (in shares)		0

Derivative Financial Instruments (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Market Based Derivative
Derivative Instruments, Gain (Loss) [Line Items]
Recognized expense on derivative	$ 2.5
Affiliated Entity \| Foreign Currency Forward Contract
Derivative Instruments, Gain (Loss) [Line Items]
Gains realized upon settlement of foreign currency forward contracts		$ 1.6	$ 0.2
Losses realized upon settlement of foreign currency forward contract on Derivative		2.2	1.2
Unrealized gains related to outstanding foreign currency contracts		0.2	0.6
Unrealized losses related to outstanding foreign currency contracts		$ 0.6	$ 0.5

Commitments and Contingencies (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Commitments and Contingencies
Co-investment commitments in partnership		$ 98,800,000
Consolidated Affiliates
Commitments and Contingencies
Other commitments		18,200,000
Other commitment, expected payments		10,200,000
Other commitments, present value of expected payments		9,400,000
Consolidated Affiliates \| Scenario, Forecast
Commitments and Contingencies
Other commitment, expected payments	$ 8,200,000
Equity Method Investee
Commitments and Contingencies
Other commitments		$ 170,000,000
Equity Method Investee \| Scenario, Forecast
Commitments and Contingencies
Other commitment, expected payments	$ 0

Fair Value Measurements - Fair Value of Financial Assets and Liabilities Measured on a Recurring Basis (Details) - Fair Value Measured on a Recurring Basis - USD ($)
$ in Millions

Dec. 31, 2017

Dec. 31, 2016

$ 40.4

$ 64.1

^[1]

57.2

40.5

^[1]

20.6

81.9

3.4

^[2]

0.2

0.6

^[2]

9.4

8.6

^[2]

49.2

12.1

^[2]

0.6

0.5

Level 1

40.4

64.1

^[1]

57.2

40.5

^[1]

20.6

81.9

3.4

^[2]

0.0

^[2]

0.0

^[2]

0.0

^[2]

0.0

Level 2

0.0

^[1]

0.0

^[1]

0.0

0.0

^[2]

0.2

0.6

^[2]

0.0

^[2]

0.0

^[2]

0.6

0.5

Level 3

0.0

^[1]

0.0

^[1]

0.0

0.0

^[2]

0.0

^[2]

9.4

8.6

^[2]

49.2

12.1

Contingent Payment Arrangements

^[2]

$ 0.0

[1]	Principally investments in equity securities.
[2]	Amounts are presented within Other assets or Other liabilities.

Fair Value Measurements - Changes in Level 3 Financial Assets and Liabilities (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Changes in level 3 assets and liabilities

Balance, beginning of period

$ 8.6

$ 10.2

Net realized and unrealized (gains) losses(1)

^[1]

7.6

(1.6)

Purchases and issuances(2)

^[2]

0.0

Settlements and reductions

(6.8)

0.0

Balance, end of period

9.4

8.6

Net change in unrealized (gains) losses relating to instruments still held at the reporting date

2.8

(1.6)

Affiliate Equity Obligations

Changes in level 3 assets and liabilities

Balance, beginning of period

12.1

62.3

Net realized and unrealized (gains) losses(1)

^[1]

5.5

3.1

Purchases and issuances(2)

^[2]

206.1

69.1

Settlements and reductions

(174.5)

(122.4)

Balance, end of period

49.2

12.1

Net change in unrealized (gains) losses relating to instruments still held at the reporting date

$ 0.0

[1]	Accretion and changes in the expected value of the Company’s contingent payment arrangements and Affiliate equity obligations are recorded in Imputed interest expense and contingent payment arrangements.
[2]	Includes transfers from Redeemable non-controlling interests and other activity.

Fair Value Measurements - Quantitative Information About Level 3 (Details) - Discounted cash flow - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Contingent payment arrangements
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair value liabilities	$ 9.4	$ 8.6
Contingent payment arrangements \| Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Growth rates	7.00%	3.00%
Discount rates	15.00%	14.00%
Contingent payment arrangements \| Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Growth rates	8.00%	8.00%
Discount rates	16.00%	15.00%
Affiliate equity obligations
Quantitative information for Level 3 Fair Value Measurements Liabilities
Fair value liabilities	$ 49.2	$ 12.1
Affiliate equity obligations \| Minimum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Growth rates	0.00%	4.00%
Discount rates	12.00%	15.00%
Affiliate equity obligations \| Maximum
Quantitative information for Level 3 Fair Value Measurements Liabilities
Growth rates	11.00%	10.00%
Discount rates	16.00%	16.00%

Fair Value Measurements - Nature of Investments and Related Liquidity (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Life of funds (in years)

15 years

Private equity

^[1]

$ 156.1

$ 137.8

Unfunded Commitments

^[1]

98.8

92.2

Other funds

^[2]

8.9

9.7

Unfunded Commitments

^[2]

0.0

Other investments | Parent

^[3]

165.0

147.5

Unfunded Commitments

^[3]

98.8

92.2

Schedule of Equity Method Investments [Line Items]

$ 80.1

$ 59.9

[1]	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 $59.9 million and $80.1 million as of December 31, 2016 and 2017, respectively.

Fair Value Measurements - Financial Liabilities not Carried at Fair Value (Details) - Level 2 - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	$ 745.7	$ 945.1
Convertible securities	309.9	307.5
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	765.2	936.0
Convertible securities	$ 549.8	$ 466.9

Goodwill and Acquired Client Relationships - Schedule of Changes in Goodwill (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Changes in goodwill
Balance, as of January 1,	$ 2,628.1	$ 2,668.4
Foreign currency translation	34.4	(40.3)
Balance, as of December 31,	$ 2,662.5	$ 2,628.1

Goodwill and Acquired Client Relationships - Schedule of Changes in Acquired Client Relationships (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Book Value
Net book value balance at the beginning of the period	$ 1,497.4
Intangible amortization and impairments	(86.4)	$ (110.2)	$ (115.4)
Net book value balance at the end of the period	1,449.7	1,497.4
Acquired Client Relationships (Net)
Definite-lived
Gross book value, balance at the beginning of the period	1,290.0	1,301.8
Accumulated amortization, balance at the beginning of the period	(788.1)	(680.4)
Net book value, balance at the beginning of the period	501.9	621.4
Intangible amortization and impairments	(86.4)	(107.7)
Foreign currency translation	5.5	(11.8)
Gross book value, balance at the end of the period	1,295.5	1,290.0	1,301.8
Accumulated amortization, balance at the end of the period	(874.5)	(788.1)	(680.4)
Net book value, balance at the end of the period	421.0	501.9	621.4
Indefinite-lived
Net book value, balance at the beginning of the period	995.5	1,065.0
Impairment	0.0	(2.5)
Foreign currency translation	33.2	(67.0)
Net book value, balance at the end of the period	1,028.7	995.5	1,065.0
Net Book Value
Net book value balance at the beginning of the period	1,497.4	1,686.4
Intangible amortization and impairments	(86.4)	(110.2)
Foreign currency translation	38.7	(78.8)
Net book value balance at the end of the period	$ 1,449.7	$ 1,497.4	$ 1,686.4

Goodwill and Acquired Client Relationships - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill
Goodwill impairment	$ 0
Definite-lived and indefinite-lived intangibles impairments		$ 0
Acquired Client Relationships (Net)
Goodwill
Intangible amortization expense		86,400,000	$ 107,700,000	$ 115,400,000
Intangible future amortization expense in 2018		85,000,000
Intangible future amortization expense in 2019		85,000,000
Intangible future amortization expense in 2020		50,000,000
Intangible future amortization expense in 2021		30,000,000
Intangible future amortization expense in 2022		$ 30,000,000

Equity Method Investments in Affiliates - Aggregate Purchase Price Allocation (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2016

Dec. 31, 2017

Dec. 31, 2015

Deferred tax liability

$ (660.8)

$ (467.4)

Goodwill

2,628.1

2,662.5

$ 2,668.4

Acquired Client Relationships (Net)

Schedule of Equity Method Investments [Line Items]

Definite-lived acquired client relationships(1)

501.9

421.0

621.4

Indefinite-lived acquired client relationships

995.5

$ 1,028.7

$ 1,065.0

2016 New Seven Equity Method Investments | Equity Method Investee

Schedule of Equity Method Investments [Line Items]

Tangible assets

2.0

Deferred tax liability

(91.8)

Goodwill

854.4

Consideration paid

1,362.3

2016 New Seven Equity Method Investments | Equity Method Investee | Acquired Client Relationships (Net)

Schedule of Equity Method Investments [Line Items]

Definite-lived acquired client relationships(1)

^[1]

560.8

Indefinite-lived acquired client relationships

$ 36.9

Expected economic benefit period of acquired client relationship intangibles

15 years

[1]	The expected period of economic benefit utilized in the purchase price allocation for these definite-lived acquired client relationships was 15 years.

Equity Method Investments in Affiliates - Additional Information (Details) - USD ($)

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Schedule of Equity Method Investments [Line Items]

Fair value assumptions, average projected growth rate

10.00%

Fair value assumptions, discount rate for asset based fees

14.00%

Fair value assumptions, discount rate for performance based fees

25.00%

Fair value assumptions, market participant tax rate

25.00%

Impairment of equity method investment

$ 93,100,000

Equity method and cost method impairments

$ 0

Revenue of equity method investment affiliate investment

^[1]

3,126,300,000

2,200,900,000

^[2]

$ 2,217,100,000

^[2]

Net income of equity method affiliate investment

^[1]

2,182,700,000

1,068,900,000

^[2]

431,500,000

^[2]

Acquired Client Relationships (Net)

Schedule of Equity Method Investments [Line Items]

Intangible amortization expense

86,400,000

107,700,000

115,400,000

Intangible future amortization expense in 2018

85,000,000

Intangible future amortization expense in 2019

85,000,000

Intangible future amortization expense in 2020

50,000,000

Intangible future amortization expense in 2021

30,000,000

Intangible future amortization expense in 2022

30,000,000

Acquired Client Relationships Under Equity Method Investments

Schedule of Equity Method Investments [Line Items]

Intangible amortization expense

106,100,000

59,200,000

$ 34,300,000

Intangible future amortization expense in 2018

120,000,000

Intangible future amortization expense in 2019

120,000,000

Intangible future amortization expense in 2020

120,000,000

Intangible future amortization expense in 2021

120,000,000

Intangible future amortization expense in 2022

120,000,000

Equity Method Investee

Schedule of Equity Method Investments [Line Items]

Revenue of equity method investment affiliate investment

1,317,800,000

944,100,000

Net income of equity method affiliate investment

806,600,000

529,000,000

2016 New Seven Equity Method Investments | Equity Method Investee | Acquired Client Relationships (Net)

Schedule of Equity Method Investments [Line Items]

Intangible amortization expense

$ 58,000,000

$ 17,000,000

[1]	Revenue and the associated Net income include asset and performance based fees and the impact of consolidated investment products.
[2]	Revenue and Net income reflect investments in new Affiliates for the full-year, regardless of the date of the Company’s investment.

Equity Method Investments in Affiliates - Change in Equity Method Investments in Affiliates (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Change in Equity Method Investments in Affiliates [Roll Forward]

Balance, January 1,

$ 3,368.3

$ 1,937.1

Equity method earnings

501.4

388.0

Equity method intangible amortization and impairments

(199.2)

(59.2)

Distributions of earnings from equity method investments

(429.8)

(346.4)

$ (346.1)

Investments

29.8

1,361.3

Foreign currency translation

62.3

8.0

Other

^[1]

(28.1)

79.5

Balance, December 31,

$ 3,304.7

$ 3,368.3

$ 1,937.1

[1]	Primarily reflects deferred income taxes recorded on new investments.

Equity Method Investments in Affiliates - Financial Information for Affiliates Accounted for Under the Equity Method (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

^[2]

Equity Method Investments and Joint Ventures [Abstract]

Revenue(1)

^[1]

$ 3,126.3

$ 2,200.9

^[2]

$ 2,217.1

Net income(1)

^[1]

2,182.7

1,068.9

^[2]

$ 431.5

Assets

3,324.9

1,915.3

Liabilities and Non-controlling interests

1,405.5

$ 862.4

Undistributed earnings from equity method affiliates

$ 192.5

[1]	Revenue and the associated Net income include asset and performance based fees and the impact of consolidated investment products.
[2]	Revenue and Net income reflect investments in new Affiliates for the full-year, regardless of the date of the Company’s investment.

Fixed Assets and Lease Commitments (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fixed assets
Fixed assets, at cost	$ 247.3	$ 234.2
Accumulated depreciation and amortization	(136.3)	(124.1)
Fixed assets, net	111.0	110.1	$ 114.1
Building and leasehold improvements
Fixed assets
Fixed assets, at cost	111.9	103.5
Software
Fixed assets
Fixed assets, at cost	50.8	52.5
Equipment
Fixed assets
Fixed assets, at cost	44.5	39.5
Furniture and fixtures
Fixed assets
Fixed assets, at cost	21.4	20.8
Land, improvements and other
Fixed assets
Fixed assets, at cost	$ 18.7	$ 17.9

Fixed Assets and Lease Commitments - Aggregate Future Minimum Payments for Operating Leases and Rent Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fixed Assets and Lease Commitments [Abstract]
2018	$ 37.0
2019	33.9
2020	35.3
2021	33.6
2022	26.6
Thereafter	89.9
Consolidated rent expense	$ 37.5	$ 35.5	$ 36.3

Payables and Accrued Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accrued compensation	$ 472.5	$ 418.5
Unsettled fund share payables	103.1	83.2
Accrued income taxes	93.0	87.7
Accrued share repurchases	23.1	0.0
Accrued professional fees	22.5	26.1
Other	93.0	113.8
Payables and accrued liabilities	$ 807.2	$ 729.3

Related Party Transactions (Details) - USD ($)	12 Months Ended
Related Party Transactions (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transactions
Imputed interest (gains) expenses of contingent payment arrangements	$ (15,500,000)	$ (3,900,000)	$ 40,300,000
Prior Owner \| Non- controlling Interests
Related Party Transactions
Investment partnerships with prior owners		2,500,000
Prior Owner \| Other Liabilities
Related Party Transactions
Investment partnerships with prior owners	61,200,000	67,800,000
Affiliated Entity
Related Party Transactions
Imputed interest (gains) expenses of contingent payment arrangements	6,600,000	(2,800,000)
Affiliated Entity \| Other Liabilities
Related Party Transactions
Contingent liabilities arrangements to related parties	9,400,000	8,600,000
Payments associated with contingent liabilities arrangements to related parties	$ 6,800,000	$ 0

Stockholders' Equity (Details) - $ / shares	12 Months Ended
Stockholders' Equity (Details) - $ / shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 31, 2017	May 31, 2015
Stockholders' equity
Common stock, shares authorized (in shares)	153,000,000	153,000,000
Common Stock
Share repurchase activity
Shares repurchased (in shares)	2,400,000	200,000	1,700,000
Average price (in usd per share)	$ 173.19	$ 161.16	$ 209.39
Common Stock \| January 2017 Plan
Stockholders' equity
Stock repurchase program, number of shares authorized (in shares)				1,900,000
Share repurchase activity
Stock repurchase plan, number of remaining shares to be repurchased (in shares)	1,600,000
Common Stock \| May 2015 Plan
Stockholders' equity
Stock repurchase program, number of shares authorized (in shares)					3,000,000
Share repurchase activity
Stock repurchase plan, number of remaining shares to be repurchased (in shares)	0
Voting Common Stock
Stockholders' equity
Common stock, shares authorized (in shares)	150,000,000.0
Class B Non-Voting Common Stock
Stockholders' equity
Common stock, shares authorized (in shares)	3,000,000.0
Preferred Stock
Share repurchase activity
Preferred stock, shares authorized (in shares)	5,000,000.0

Share-Based Compensation - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Total fair value of share-based compensation awards vested	$ 59.4	$ 20.7	$ 27.4
Excess tax benefit recognized from share-based incentive plans	10.9	5.1
Total compensation cost not yet recognized	$ 63.5	$ 66.4
Weighted average period for recognition (in years)	2 years

Share-Based Compensation - Share-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Compensation Expense	$ 40.4	$ 39.2	$ 34.2
Tax Benefit	$ 13.6	$ 15.1	$ 13.2

Share-Based Compensation - Transactions of the Company's Stock Options (Details) shares in Millions	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Stock Options
Stock options outstanding at the beginning of the period (in shares) \| shares	1.4
Options granted (in shares) \| shares	0.0
Options exercised (in shares) \| shares	(0.7)
Options forfeited (in shares) \| shares	(0.1)
Stock options outstanding at the end of the period (in shares) \| shares	0.6
Exercisable stock options, at the end of the period (in shares) \| shares	0.2
Weighted Average Exercise Price
Stock options outstanding, at the beginning of the period (in usd per share) \| $ / shares	$ 108.53
Options granted (in usd per share) \| $ / shares	168.60
Options exercised (in usd per share) \| $ / shares	97.54
Options forfeited (in usd per share) \| $ / shares	140.26
Stock options outstanding, at the end of the period (in usd per share) \| $ / shares	122.04
Exercisable stock options, at the end of the period (in usd per share) \| $ / shares	$ 115.74
Weighted Average Remaining Contractual Life (years)
Stock options outstanding, at the end of the period (in years)	3 years 10 months 24 days
Exercisable stock options, at the end of the period (in years)	1 year 8 months 12 days

Share-Based Compensation - Stock Options Narrative (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award
Fair value of stock options granted	$ 0.8	$ 16.4	$ 1.0
Total intrinsic value of options exercised	50.8	27.7	$ 130.2
Cash received for options exercised	41.9	$ 25.6
Intrinsic value of exercisable options outstanding	$ 20.1
Weighted average fair value of options granted (in usd per share)	$ 48.05	$ 39.02	$ 54.92
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award
Options available for future grant under the Company's option plans (in shares)	3.1
Stock Options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period of options	3 years
Expiration period of options	7 years
Stock Options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period of options	4 years

Share-Based Compensation - Assumptions Used to Determine Fair Value of Options Granted (Details) - Stock Options

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Assumptions used to determine fair value of options granted

Dividend yield

0.50%

0.00%

Expected volatility

^[1]

28.00%

30.70%

26.70%

Risk-free interest rate

^[2]

2.10%

1.60%

1.50%

Expected life of options (in years)

^[3]

5 years 8 months 12 days

5 years

Forfeiture rate

0.00%

[1]	Expected volatility is based on historical and implied volatility.
[2]	Risk-free interest rate is based on the U.S. Treasury yield curve in effect at the date of grant.
[3]	Expected life of options (in years) is based on the Company’s historical and expected exercise behavior.

Share-Based Compensation - Transactions of the Company's Restricted Stock (Details) - Restricted Stock shares in Millions	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Restricted Stock
Units outstanding at the beginning of the period (in shares) \| shares	0.6
Units granted (in shares) \| shares	0.2
Units vested (in shares) \| shares	(0.4)
Units forfeited (in shares) \| shares	0.0
Units outstanding at the end of the period (in shares) \| shares	0.4
Weighted Average Grant Date Value
Units outstanding at the beginning of the period (in usd per share) \| $ / shares	$ 168.84
Units granted (in usd per share) \| $ / shares	152.99
Units vested (in usd per share) \| $ / shares	166.22
Units forfeited (in usd per share) \| $ / shares	170.39
Units outstanding at the end of the period (in usd per share) \| $ / shares	$ 162.32

Share-Based Compensation - Restricted Stock Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award
Fair value of restricted stocks granted	$ 59.4	$ 20.7	$ 27.4
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award
Fair value of restricted stocks granted	$ 36.9	$ 28.0	$ 50.7
Restricted stocks available for future grant under the Company's option plans (in shares)	1,100,000.0
Restricted Stock \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period of restricted stocks	3 years
Restricted Stock \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period of restricted stocks	4 years

Redeemable Non-Controlling Interests (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in redeemable non-controlling interests during the period
Balance, as of January 1,	$ 673.5	$ 612.5
Changes attributable to consolidated products	12.4	16.1
Transfers to Other liabilities	(192.3)	(69.1)
Transfers from non-controlling interests	76.8	42.6
Changes in redemption value	241.5	71.4	$ 81.6
Balance, as of December 31,	$ 811.9	$ 673.5	$ 612.5
Minimum
Noncontrolling Interest [Line Items]
Term of conditional right put interest	5 years
Maximum
Noncontrolling Interest [Line Items]
Term of conditional right put interest	15 years

Affiliate Equity - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Affiliate Equity
Distributions paid to affiliate partners	$ 352.2	$ 354.1	$ 431.4
Payments to acquire interest in affiliates	174.7	115.8	130.8
Issuance of interest in affiliates	9.0	11.8	$ 6.1
Other Assets
Affiliate Equity
Due from affiliates	12.4	22.9
Other Liabilities
Affiliate Equity
Due to affiliates	$ 49.2	$ 12.1
Minimum
Affiliate Equity
Affiliate equity, conditional right to put interest, period	5 years
Maximum
Affiliate Equity
Affiliate equity, conditional right to put interest, period	15 years

Affiliate Equity - Recognized and Unrecognized Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Affiliate Equity Expense
Non-controlling interest	$ 36.8	$ 31.2	$ 51.6
Total	50.0	41.2	68.5
Non- controlling Interests
Affiliate Equity Expense
Total	$ 36.8	$ 31.2	$ 51.6
Unrecognized Affiliate Equity Expense
Remaining Life	6 years	5 years	5 years
Non-Controlling Interest	$ 95.9	$ 70.7	$ 51.9
Controlling Interest
Affiliate Equity Expense
Controlling interest	13.2	10.0	16.9
Unrecognized Affiliate Equity Expense
Controlling Interest	$ 33.3	$ 31.3	$ 22.4
Remaining Life	5 years	4 years	3 years

Affiliate Equity - Effect of Changes in the Company's Ownership Interest in its Affiliates on the Controlling Interest's Equity (Details) - USD ($)
$ in Millions

3 Months Ended

12 Months Ended

Dec. 31, 2017

^[1]

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Affiliate Equity [Abstract]

Net income (controlling interest)

$ 315.4

$ 125.4

$ 126.3

$ 122.5

$ 150.2

$ 110.2

$ 108.3

$ 104.0

$ 689.5

$ 472.8

$ 509.5

Increase / (decrease) in controlling interest paid-in capital from purchases and sales of Affiliate equity issuances

(1.0)

1.6

0.9

Decrease in controlling interest paid-in capital related to Affiliate equity repurchases

(116.2)

(38.0)

(87.6)

Net income attributable to controlling interest and transfers from non-controlling interests

$ 572.3

$ 436.4

$ 422.8

[1]	In the fourth quarter of 2017, the Company recorded a provisional one-time net benefit from changes in U.S tax laws (see Note 22) and an expense associated with the impairment of one of its Affiliates accounted for under the equity method (see Note 13).

Benefit Plans Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Expenses related to qualified defined contribution plans	$ 20.1	$ 18.9	$ 18.7
Non- controlling Interests
Defined Benefit Plan Disclosure [Line Items]
Expenses related to qualified defined contribution plans	$ 3.9	$ 3.7	$ 3.1

Income Taxes - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Provisional one-time net benefit from changes in U.S. tax laws	$ 194.1
Net income tax benefit resulting from re-measurement of Company's deferred tax assets and liabilities	216.9
Provisional amount for repatriation tax liability	$ 22.8
State net operating loss carryforwards, expiration period	19 years
Foreign operating loss carryforwards, expiration period	20 years
Operating loss carryforwards, valuation allowance	$ 24.1	$ 22.1
Amount of temporary difference due to repatriation of earnings from sale or liquidation of subsidiary	270.9
Unrecognized tax benefits that, if recognized, would affect effective tax rate	32.4	26.0	$ 25.3
Accrued income tax interest and related charges	1.7	1.4	$ 1.8
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	432.6
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	61.5
Foreign Tax Authority \| Valuation Allowance, Operating Loss Carryforwards
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, valuation allowance	24.1
Increase in valuation allowance, state net operating loss carryforward and realized deferred tax benefit	2.0	$ 1.6
Foreign Tax Authority \| Expire over a 20-year period
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 51.8

Income Taxes - Income Tax Provision Attributable to Controlling and Non-Controlling Interests (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Provision for income taxes

Current tax

$ 182.0

$ 176.3

$ 162.2

Deferred taxes

(123.6)

59.3

101.2

$ 58.4

$ 235.6

$ 263.4

Effective tax rate attributable to controlling interests

6.80%

32.60%

33.60%

Controlling interests

Intangible-related deferred taxes

Current tax

$ 173.8

$ 168.1

$ 152.4

(98.5)

84.3

77.7

Other deferred taxes

(24.9)

(23.2)

27.7

Provision for income taxes

50.4

229.2

257.8

Income before income taxes (controlling interest)

$ 739.9

$ 702.0

$ 767.3

Effective tax rate attributable to controlling interests

^[1]

6.80%

32.60%

33.60%

Non-Controlling Interests

Provision for income taxes

Current tax

$ 8.2

$ 9.8

Deferred taxes

(0.2)

(1.8)

(4.2)

$ 8.0

$ 6.4

$ 5.6

[1]	Taxes attributable to the controlling interest divided by Income before income taxes (controlling interest).

Income Taxes - Consolidated Provision for Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 109.0	$ 103.4	$ 106.3
State	18.9	22.9	18.3
Foreign	54.1	50.0	37.6
Total current	182.0	176.3	162.2
Deferred:
Federal	(124.9)	62.3	103.8
State	10.4	10.0	14.8
Foreign	(9.1)	(13.0)	(17.4)
Total deferred	(123.6)	59.3	101.2
Provision for income taxes	$ 58.4	$ 235.6	$ 263.4

Income Taxes - Components of Income Before Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic	$ 756.5	$ 688.1	$ 827.6
International	310.6	286.5	263.0
Total	$ 1,067.1	$ 974.6	$ 1,090.6

Income Taxes - Reconciliation of U.S. Federal Statutory Tax Rate to Company's Effective Tax Rate (Details)

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Statutory U.S. federal tax rate

35.00%

State income taxes, net of federal benefit

2.70%

2.90%

2.60%

Effect of foreign operations

(5.40%)

(4.60%)

(3.50%)

Equity compensation

(0.70%)

(0.40%)

0.80%

Effect of changes in tax law, rates

(25.20%)

(0.30%)

(0.80%)

Other

0.40%

0.00%

(0.50%)

Effective tax rate (controlling interest)

6.80%

32.60%

33.60%

Non-Controlling Interests

Effect of income from non-controlling interests

(1.30%)

(8.40%)

(9.20%)

Controlling interests

Effective tax rate (controlling interest)

^[1]

6.80%

32.60%

33.60%

Effective tax rate

5.50%

24.20%

24.40%

[1]	Taxes attributable to the controlling interest divided by Income before income taxes (controlling interest).

Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets
State net operating loss carryforwards	$ 16.8	$ 17.4
Foreign loss carryforwards	16.3	14.6
Tax benefit of uncertain tax positions	11.4	12.1
Deferred compensation	10.4	34.1
Foreign tax credits	0.0	10.0
Accrued expenses	1.3	3.9
Total deferred tax assets	56.2	92.1
Valuation allowance	(24.1)	(22.1)
Deferred tax assets, net of valuation allowance	32.1	70.0
Deferred Tax Liabilities
Intangible asset amortization	(258.6)	(396.8)
Non-deductible intangible amortization	(150.8)	(177.0)
Convertible securities interest	(77.9)	(109.0)
Deferred income	(5.9)	(47.2)
Other	(6.3)	(0.8)
Total deferred tax liabilities	(499.5)	(730.8)
Deferred income tax liability (net)	$ (467.4)	$ (660.8)

Income Taxes - Changes in Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of beginning and ending amount of unrecognized tax benefits
Balance, as of January 1,	$ 26.8	$ 26.9	$ 28.8
Additions based on current year tax positions	6.0	3.8	2.2
Additions based on prior years’ tax positions	1.5	0.6	1.6
Reductions related to lapses of statutes of limitations	(2.3)	(4.7)	(4.3)
Additions (reductions) related to foreign exchange rates	0.4	0.2	(1.4)
Balance, as of December 31,	$ 32.4	$ 26.8	$ 26.9

Earnings Per Share - Reconciliation of the Numerator and Denominator used in the Calculation of Basic and Diluted Earnings per Share (Details) - USD ($)
shares in Millions, $ in Millions

3 Months Ended

12 Months Ended

Dec. 31, 2017

^[1]

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Numerator

Net income (controlling interest)

$ 315.4

$ 125.4

$ 126.3

$ 122.5

$ 150.2

$ 110.2

$ 108.3

$ 104.0

$ 689.5

$ 472.8

$ 509.5

Interest expense on convertible securities, net of taxes

15.5

15.3

Net income (controlling interest), as adjusted

$ 705.0

$ 488.3

$ 524.8

Denominator

Average shares outstanding - basic (in shares)

56.0

54.2

54.3

Effect of dilutive instruments:

Stock options and restricted stock units (in shares)

0.4

0.6

0.7

Junior convertible securities (in shares)

2.2

Average shares outstanding - diluted (in shares)

58.6

57.0

57.2

[1]	In the fourth quarter of 2017, the Company recorded a provisional one-time net benefit from changes in U.S tax laws (see Note 22) and an expense associated with the impairment of one of its Affiliates accounted for under the equity method (see Note 13).

Earnings Per Share - Diluted Earnings per Share Calculations Excluding the Anti-dilutive Effect of Shares (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock options and restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	0.1	0.6	0.0

Comprehensive Income - Tax Effects Allocated to Each Component of Other Comprehensive Income (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

$ 112.3

$ (173.3)

$ (56.1)

7.2

22.9

(13.1)

Foreign currency translation adjustment

119.5

(150.4)

(69.2)

128.0

(115.3)

(93.2)

0.0

Change in net realized and unrealized gain (loss) on derivative securities

128.0

(115.3)

(93.2)

(0.7)

0.3

2.3

(0.1)

(0.2)

(0.4)

Change in net unrealized gain (loss) on investment securities

(0.8)

0.1

1.9

(15.0)

(58.3)

34.8

7.3

23.1

(12.7)

Accumulated Other Comprehensive Income (Loss) Net of Tax [Roll Forward]

$ (7.7)

^[1]

$ (35.2)

^[1]

$ 22.1

[1]	See Note 2 for amounts reclassified from Other comprehensive income (loss).

Comprehensive Income - Components of Accumulated Other Comprehensive Income, Net of Taxes (Details) - USD ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Other comprehensive gain (loss) before reclassifications

$ 4,426.5

$ 3,769.1

$ 3,643.2

142.1

(138.8)

(22.6)

(11.6)

119.5

(150.4)

(69.2)

Foreign Currency Translation Adjustment

4,578.5

4,426.5

3,769.1

Accumulated Other Comprehensive Income (Loss) Net of Tax [Roll Forward]

Other comprehensive gain (loss) before reclassifications

(213.9)

(98.6)

128.0

(115.3)

0.0

128.0

(115.3)

(93.2)

Realized and Unrealized Gains (Losses) on Derivative Securities

(85.9)

(213.9)

(98.6)

Accumulated Other Comprehensive Income (Loss) Net of Tax [Roll Forward]

Other comprehensive gain (loss) before reclassifications

0.4

0.3

(1.6)

(1.0)

0.8

1.1

(0.8)

0.1

1.9

Change in net unrealized gain (loss) on investment securities

(0.4)

0.4

0.3

Accumulated Other Comprehensive Income (Loss) Net of Tax [Roll Forward]

Other comprehensive gain (loss) before reclassifications

^[1]

9.8

45.0

^[1]

15.7

(22.5)

^[1]

(23.4)

(12.7)

(7.7)

^[1]

(35.2)

^[1]

22.1

Accumulated Other Comprehensive Income (Loss) Net of Tax [Roll Forward]

^[1]

2.1

9.8

45.0

Total

(203.7)

(53.3)

Quarterly Financial Information Disclosure [Abstract]

$ (84.2)

$ (203.7)

$ (53.3)

[1]	See Note 2 for amounts reclassified from Other comprehensive income (loss).

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($)
$ / shares in Units, $ in Millions

3 Months Ended

12 Months Ended

Dec. 31, 2017

^[1]

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Income before income taxes

$ 604.1

$ 585.7

$ 570.9

$ 544.3

$ 550.3

$ 544.7

$ 554.1

$ 545.4

$ 2,305.0

$ 2,194.6

$ 2,484.5

Operating income

280.0

289.5

275.9

262.5

301.9

238.5

247.0

246.8

1,107.9

1,034.1

1,123.9

264.0

282.9

266.9

253.3

281.9

226.2

235.9

230.5

1,067.1

974.6

1,090.6

Net income (controlling interest)

$ 315.4

$ 125.4

$ 126.3

$ 122.5

$ 150.2

$ 110.2

$ 108.3

$ 104.0

$ 689.5

$ 472.8

$ 509.5

Earnings per share - diluted (in dollars per share)

$ 5.50

$ 2.22

$ 2.13

$ 2.67

$ 2.02

$ 1.98

$ 1.90

$ 12.03

$ 8.57

$ 9.17

[1]	In the fourth quarter of 2017, the Company recorded a provisional one-time net benefit from changes in U.S tax laws (see Note 22) and an expense associated with the impairment of one of its Affiliates accounted for under the equity method (see Note 13).

Segment and Geographic Information - Additional Information (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2017 segment channel	Dec. 31, 2017 segment	Dec. 31, 2016 segment
Segment Reporting [Abstract]
Number of operating segments		1
Number of reportable segments	1		3
Number of principal distribution channels \| channel	3

Segment and Geographic Information - Revenues and Assets by Geographic Location (Details) - USD ($)
$ in Millions

3 Months Ended

12 Months Ended

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

$ 604.1

^[1]

$ 585.7

$ 570.9

$ 544.3

$ 550.3

$ 544.7

$ 554.1

$ 545.4

$ 2,305.0

$ 2,194.6

$ 2,484.5

111.0

110.1

111.0

110.1

114.1

United States

1,571.4

1,477.5

1,657.2

97.8

97.3

97.8

97.3

98.6

United Kingdom

587.3

566.4

645.3

11.4

9.9

11.4

9.9

12.3

Other

146.3

150.7

182.0