Investments - Net Investment Gains (Losses) of Consolidated Funds (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Investments [Abstract]
Gains (losses) from investments of Consolidated Funds	$ 163.1	$ 0.6	$ (219.2)	$ 18.8
Gains (losses) from liabilities of CLOs	(139.2)	(2.5)	180.3	(25.7)
Total	$ 23.9	$ (1.9)	$ (38.9)	$ (6.9)