Investments - Interest and Other Income of Consolidated Funds (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments [Abstract]
Interest income from investments	$ 192.3	$ 207.2	$ 167.3
Other income	6.9	7.3	10.4
Total	$ 199.2	$ 214.5	$ 177.7