COMMITMENTS AND CONTINGENCIES - Narrative (Details) - USD ($)	3 Months Ended	4 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2021	Jul. 01, 2021	Dec. 31, 2020
COMMITMENTS AND CONTINGENCIES
Unfunded capital commitments	$ 732,800,000	$ 732,800,000	$ 732,800,000		$ 784,200,000
Performance Income
Carried interest, contingent repayment obligations	0	0	0		0
Performance income
Performance Income
Performance income subject to potential clawback provision	202,300,000	202,300,000	202,300,000		326,400,000
Performance income subject to potential claw back provision that are reimbursable by professionals	158,000,000	158,000,000	158,000,000		$ 252,400,000
Landmark Acquisition
COMMITMENTS AND CONTINGENCIES
Commitment, maximum amount	300,000,000	300,000,000	$ 300,000,000
Business combination, percentage			15.00%
Business combination equity awards percentage			85.00%
Vesting period			4 years
Estimated fair value of the contingent consideration liability	236,000,000	236,000,000	$ 236,000,000
Compensation expense	14,700,000	19,300,000
Black Creek Acquisition
COMMITMENTS AND CONTINGENCIES
Commitment, maximum amount	275,000,000	275,000,000	275,000,000
Compensation expense	13,500,000
Fair value of contingent liability	206,700,000	206,700,000	206,700,000
Contingent consideration	32,800,000	32,800,000	32,800,000	$ 28,600,000
Payment percentage of performance income obligation				50.00%
Black Creek Acquisition | Accrued Compensation
COMMITMENTS AND CONTINGENCIES
Contingent consideration	$ 13,500,000	$ 13,500,000	$ 13,500,000