DERIVATIVES AND HEDGING - Impact of Derivatives Held by Consolidated Funds on Income (Details) - Not Designated as Hedging Instrument - Consolidated Funds - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivatives, Fair Value [Line Items]
Net Realized Gain (Loss) on Investments	$ (1,262)	$ (1,969)	$ (3,873)	$ (2,239)
Net Change in Unrealized Appreciation (Depreciation) on Investments	(257)	1,131	854	(1,022)
Foreign-currency forward contracts
Derivatives, Fair Value [Line Items]
Net Realized Gain (Loss) on Investments	(569)	(298)	(390)	(500)
Net Change in Unrealized Appreciation (Depreciation) on Investments	(96)	849	(410)	457
Total-return and interest-rate swaps
Derivatives, Fair Value [Line Items]
Net Realized Gain (Loss) on Investments	(722)	(907)	(1,468)	(890)
Net Change in Unrealized Appreciation (Depreciation) on Investments	(237)	222	998	(1,396)
Options and futures
Derivatives, Fair Value [Line Items]
Net Realized Gain (Loss) on Investments	29	(764)	(2,015)	(849)
Net Change in Unrealized Appreciation (Depreciation) on Investments	$ 76	$ 60	$ 266	$ (83)