INVESTMENTS - Net Gains (Losses) from Investment Activities of Consolidated Funds (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	$ (19,635)	$ (3,664)	$ (97,642)	$ (9,036)
Net Change in Unrealized Appreciation (Depreciation) on Investments	533	(40,964)	(222,746)	17,967
Consolidated Funds
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	(19,635)	(3,664)	(97,642)	(9,036)
Net Change in Unrealized Appreciation (Depreciation) on Investments	533	(40,964)	(222,746)	17,967
Consolidated Funds | Investments and other financial instruments
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	(19,781)	636	(86,506)	(7,076)
Net Change in Unrealized Appreciation (Depreciation) on Investments	118,110	(14,910)	(325,510)	137,322
Consolidated Funds | CLO Liabilities
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	0	0	0	0
Net Change in Unrealized Appreciation (Depreciation) on Investments	(117,948)	(25,778)	126,410	(119,767)
Consolidated Funds | Foreign-currency forward contracts
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	192	(4,300)	(11,200)	(1,960)
Net Change in Unrealized Appreciation (Depreciation) on Investments	417	(276)	(23,483)	412
Consolidated Funds | Options and futures
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	(114)	0	(4)	0
Net Change in Unrealized Appreciation (Depreciation) on Investments	(40)	0	(157)	0
Consolidated Funds | Total-return and interest-rate swaps
Gain (Loss) on Securities [Line Items]
Net Realized Gain (Loss) on Investments	68	0	68	0
Net Change in Unrealized Appreciation (Depreciation) on Investments	$ (6)	$ 0	$ (6)	$ 0