DERIVATIVES AND HEDGING - Impact of Derivatives Held by the Consolidated Fund on the Consolidated Statements of Operations (Details) - Consolidated Funds - Not Designated as Hedging Instrument - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Net Realized Gain (Loss) on Investments	$ (6,546)	$ 2,581	$ (7,510)
Net Change in Unrealized Appreciation (Depreciation) on Investments	4,364	2,432	2,861
Foreign-currency forward contracts
Derivatives, Fair Value [Line Items]
Net Realized Gain (Loss) on Investments	(6,546)	513	(2,917)
Net Change in Unrealized Appreciation (Depreciation) on Investments	4,364	2,327	1,909
Total-return and interest-rate swaps
Derivatives, Fair Value [Line Items]
Net Realized Gain (Loss) on Investments	0	858	232
Net Change in Unrealized Appreciation (Depreciation) on Investments	0	29	378
Options and futures
Derivatives, Fair Value [Line Items]
Net Realized Gain (Loss) on Investments	0	1,210	(4,825)
Net Change in Unrealized Appreciation (Depreciation) on Investments	$ 0	$ 76	$ 574