INVESTMENTS - Other Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Realized gain (loss)	$ (17,773)	$ (23,528)	$ 20,400
Net change in unrealized appreciation (depreciation) on consolidated funds’ investments	9,937	(164,592)	55,061
Total gain (loss)	(7,836)	(188,120)	75,461
Other Investments, at Fair Value
Schedule of Investments [Line Items]
Realized gain (loss)	7,763	18,208	8,439
Net change in unrealized appreciation (depreciation) on consolidated funds’ investments	13,186	(1,888)	(16,926)
Total gain (loss)	$ 20,949	$ 16,320	$ (8,487)