Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Millions	Total	Consolidated Entity Excluding Consolidated Funds Common stock	Consolidated Entity Excluding Consolidated Funds Additional paid-in capital	Consolidated Entity Excluding Consolidated Funds Retained earnings (deficit)	Consolidated Entity Excluding Consolidated Funds Accumulated other comprehensive income (loss)	Consolidated Entity Excluding Consolidated Funds Total shareholders’ equity	Consolidated Entity Excluding Consolidated Funds Non-controlling interests	Consolidated Funds	Consolidated Funds Non-controlling interests
Beginning balance (in shares) at Dec. 31, 2016		114,100,000
Balance beginning at Dec. 31, 2016	$ 165.0	$ 0.1	$ 890.0	$ (699.8)	$ (26.3)	$ 164.0	$ 1.0		$ 0.0
Increase (Decrease) in Stockholders' Equity
Issuance of ordinary shares (in shares)		600,000
Repurchase of ordinary shares (in shares)	0	(5,000,000.0)
Repurchase of common stock	$ (73.1)		(73.1)			(73.1)
Capital contributions (redemptions)	(1.1)		(1.1)			(1.1)		$ 33.4
Equity-based compensation	15.7		15.7			15.7
Foreign currency translation adjustment	2.9				2.9	2.9
Amortization of derivative securities, net of tax	1.8				1.8	1.8
Other changes in non-controlling interests	(0.3)						(0.3)
Net consolidation (de-consolidation) of Funds	50.9								50.9
Dividends to shareholders	(27.7)			(27.7)		(27.7)
Dividends to related parties	(11.3)			(11.3)		(11.3)
Net income	3.9			4.2		4.2			(0.3)
Ending balance (in shares) at Dec. 31, 2017		109,700,000
Balance end at Dec. 31, 2017	127.3	$ 0.1	831.5	(734.6)	(21.6)	75.4	1.3		50.6
Balance start at Dec. 31, 2016								5.5
Increase (Decrease) in redeemable non-controlling interest in consolidated Funds
Net de-consolidation of Funds								(0.1)
Net income								5.2
Balance end at Dec. 31, 2017								44.0
Beginning balance at Dec. 31, 2016	170.5
Increase (Decrease) in total equity and redeemable non-controlling interest in consolidated Funds
Issuance of common stock	0.0
Repurchase of common stock	(73.1)
Capital contributions (redemptions)	32.3
Equity-based compensation	15.7
Foreign currency translation adjustment	2.9
Amortization of derivative securities, net of tax	1.8
Amendment of deferred tax asset deed	0.0
Net de-consolidation of Funds	50.8
Dividends to shareholders	(27.7)
Dividends to related parties	(11.3)
Net income (loss)	9.1
Ending balance at Dec. 31, 2017	$ 171.3
Increase (Decrease) in Stockholders' Equity
Issuance of ordinary shares (in shares)		1,000,000.0
Repurchase of ordinary shares (in shares)	(5,549,861)	(5,500,000)
Repurchase of common stock	$ (74.6)		(74.6)			(74.6)
Capital contributions (redemptions)	9.3								9.3
Equity-based compensation	7.7		7.7			7.7
Foreign currency translation adjustment	(1.7)				(1.7)	(1.7)
Amortization of derivative securities, net of tax	2.4				2.4	2.4
Other changes in non-controlling interests	(0.3)						(0.3)
Net consolidation (de-consolidation) of Funds	(28.8)								(28.8)
Dividends to shareholders	(42.3)			(42.3)		(42.3)
Net income	134.6			136.4		136.4			(1.8)
Ending balance (in shares) at Dec. 31, 2018		105,200,000
Balance end at Dec. 31, 2018	134.2	$ 0.1	764.6	(640.5)	(20.9)	103.3	1.6		29.3
Increase (Decrease) in redeemable non-controlling interest in consolidated Funds
Net de-consolidation of Funds								(76.7)
Capital redemptions								78.9
Net income								(4.3)
Balance end at Dec. 31, 2018								41.9
Increase (Decrease) in total equity and redeemable non-controlling interest in consolidated Funds
Issuance of common stock	0.0
Repurchase of common stock	(74.6)
Capital contributions (redemptions)	88.2
Equity-based compensation	7.7
Foreign currency translation adjustment	(1.7)
Amortization of derivative securities, net of tax	2.4
Net de-consolidation of Funds	(105.5)
Dividends to shareholders	(42.3)
Net income (loss)	130.3
Ending balance at Dec. 31, 2018	$ 176.1
Increase (Decrease) in Stockholders' Equity
Issuance of ordinary shares (in shares)		200,000
Repurchase of ordinary shares (in shares)	(19,479,945)	(19,500,000)
Repurchase of common stock	$ (236.5)		(236.5)			(236.5)
Capital contributions (redemptions)	9.2								9.2
Equity-based compensation	6.2		6.2			6.2
Foreign currency translation adjustment	1.0				1.0	1.0
Amortization of derivative securities, net of tax	2.4				2.4	2.4
Other changes in non-controlling interests	(0.3)						(0.3)
Dividends to shareholders	(35.9)			(35.9)		(35.9)
Net income	234.2			223.9		223.9			10.3
Ending balance (in shares) at Dec. 31, 2019		85,900,000
Balance end at Dec. 31, 2019	114.5	$ 0.1	$ 534.3	$ (452.5)	$ (17.5)	$ 64.4	$ 1.3		$ 48.8
Increase (Decrease) in redeemable non-controlling interest in consolidated Funds
Capital redemptions								36.2
Net income								5.8
Balance end at Dec. 31, 2019								$ 83.9
Increase (Decrease) in total equity and redeemable non-controlling interest in consolidated Funds
Issuance of common stock	0.0
Repurchase of common stock	(236.5)
Capital contributions (redemptions)	45.4
Equity-based compensation	6.2
Foreign currency translation adjustment	1.0
Amortization of derivative securities, net of tax	2.4
Dividends to shareholders	(35.9)
Net income (loss)	240.0
Ending balance at Dec. 31, 2019	$ 198.4