UNCONSOLIDATED INVESTMENTS - Income from Unconsolidated Investments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Equity Method Investments and Joint Ventures [Abstract]
Income from unconsolidated investments - operating performance	$ 80.2	$ 60.7	$ 43.4
Income from unconsolidated investments - realized gains from cost basis investments	4.7	0.0	0.0
Income from unconsolidated investments - unrealized and realized fair value gains	114.6	213.5	47.2
Income from unconsolidated investments - realized losses and impairment	0.0	(3.1)	(12.3)
Principal co-investments	199.5	271.1	78.3
(Loss) income from unconsolidated investments - performance allocation	(21.1)	117.9	2.7
Total interest income and foreign currency gain (loss)	$ 178.4	$ 389.0	$ 81.0