Investments - Net Investment Gains (Losses) of Consolidated Funds (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Equity Method Investments and Joint Ventures [Abstract]
Gains (losses) from investments of Consolidated Funds	$ 18.6	$ (337.8)	$ 45.0	$ 738.1
Gains (losses) from liabilities of CLOs	(15.9)	306.6	(43.8)	197.0
Gains (losses) on other assets of CLOs	2.1	(0.1)	1.9	0.7
Total	$ 4.8	$ (31.3)	$ 3.1	$ 935.8