COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended
	May 31, 2018	Aug. 31, 2014	Mar. 31, 2019	Mar. 31, 2020	Dec. 31, 2019
Contingencies And Commitments [Line Items]
Accrued incentives (fund level)				$ 627,398	$ 864,900
Compensation expense related to accrued incentives (fund level)				334,720	462,684
Capital commitments				266,600	237,300
Highstar Capital
Contingencies And Commitments [Line Items]
Contingent consideration	$ 36,100	$ 60,000
Period of performance		7 years
Reduction in contingent consideration liability	$ 7,100
Contingent consideration, fair value			$ 6,600	0
Contingent consideration income (expense)			$ 100
Consolidated Funds
Contingencies And Commitments [Line Items]
Aggregate potential credit and investment commitments				$ 1,300	$ 2,300