Unconsolidated Investments - Income From Unconsolidated Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Equity Method Investments and Joint Ventures [Abstract]
Income from unconsolidated investments - operating performance	$ 17.9	$ 8.7	$ 44.0	$ 32.0
Income from unconsolidated investments - realized losses	0.0	0.0	0.0	(0.6)
Income from unconsolidated investments - fair value	78.9	14.2	111.0	22.8
Income from unconsolidated investments - performance fees	46.3	(1.3)	62.0	(2.5)
Income from unconsolidated investments - impairment	0.0	(6.7)	(3.1)	(6.7)
Income from unconsolidated investments	$ 143.1	$ 14.9	$ 213.9	$ 45.0