CONSOLIDATION - Variable Interest Entities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Variable Interest Entity [Line Items]
Assets of consolidated VIEs	$ 19,934,398		$ 19,934,398		$ 15,168,992
Liabilities of consolidated VIEs	15,295,223		15,295,223		12,596,852
Collateralized loan obligations and other fixed income, at fair value
Variable Interest Entity [Line Items]
Maximum exposure to loss attributable to the company's investment in VIEs	104,400		104,400		107,700
Consolidated Funds
Variable Interest Entity [Line Items]
Net income (loss) attributable to non-controlling interests related to consolidated VIEs	47,370	$ 42,627	102,255	$ (38,593)
Non-Consolidated Variable Interest Entities
Variable Interest Entity [Line Items]
Maximum exposure to loss attributable to the company's investment in VIEs	340,988		340,988		224,203
Consolidated VIEs
Variable Interest Entity [Line Items]
Maximum exposure to loss attributable to the company's investment in VIEs	478,164		478,164		391,963
Consolidated VIEs | Consolidated Funds
Variable Interest Entity [Line Items]
Assets of consolidated VIEs	12,190,617		12,190,617		11,580,003
Liabilities of consolidated VIEs	11,238,928		11,238,928		$ 10,716,438
Net income (loss) attributable to non-controlling interests related to consolidated VIEs	$ 38,597	$ 42,627	$ 84,285	$ (38,593)