Investments - Realized and Unrealized Gains (Losses) Earned from Investments of Consolidated Funds (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Investments [Abstract]
Realized gains (losses)	$ (10.7)	$ (9.6)	$ 6.5	$ (49.9)
Net change in unrealized gains (losses)	8.2	172.7	93.8	(169.3)
Total	$ (2.5)	$ 163.1	$ 100.3	$ (219.2)