DERIVATIVES AND HEDGING - Fair Value of Derivatives of Consolidated Funds (Details) - Not Designated as Hedging Instrument - Consolidated Funds - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets
Notional	$ 298,233
Fair Value	8,618
Liabilities
Notional	(421,760)
Fair Value	(27,475)
Foreign-currency forward contracts
Assets
Notional	298,233	$ 166,917
Fair Value	8,618	6,890
Liabilities
Notional	(416,251)	(140,276)
Fair Value	(27,353)	$ (2,551)
Options and futures
Assets
Notional	0
Fair Value	0
Liabilities
Notional	(5,509)
Fair Value	$ (122)