DEBT OBLIGATIONS AND CREDIT FACILITIES - Collateralized Loan Obligation Loans Payable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Fair value		$ 4,127,994
Consolidated Funds
Debt Instrument [Line Items]
Fair value	$ 5,767,999
Consolidated Funds | Senior notes
Debt Instrument [Line Items]
Fair value	$ 5,613,846	$ 3,976,602
Weighted Average Interest Rate	2.85%	2.69%
Weighted Average Remaining Maturity (years)	8 years 7 months 6 days	9 years 10 months 24 days
Consolidated Funds | Subordinated Notes
Debt Instrument [Line Items]
Fair value	$ 154,153	$ 151,392
Weighted Average Remaining Maturity (years)	10 years 4 months 24 days	9 years 8 months 12 days