REVENUES - Revenues Disaggregated by Fund Structure (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 45,582	$ 205,190	$ 181,810	$ 785,088
Management Fees
Disaggregation of Revenue [Line Items]
Revenues	45,466	179,761	138,278	524,798
Closed-end
Disaggregation of Revenue [Line Items]
Revenues	765	120,462	1,404	345,091
Open-end
Disaggregation of Revenue [Line Items]
Revenues	2,553	29,990	6,808	90,480
Evergreen
Disaggregation of Revenue [Line Items]
Revenues	0	29,309	0	89,227
Sub-advisory fees
Disaggregation of Revenue [Line Items]
Revenues	42,148	0	130,066	0
Incentive Income
Disaggregation of Revenue [Line Items]
Revenues	$ 116	$ 25,429	$ 43,532	$ 260,290