SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Condensed Consolidated Statement of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net income (loss)	$ 14,169	$ 113,827	$ 88,590	$ (42,497)
Cash flows due to changes in operating assets and liabilities			66,925	(144,249)
Consolidated Funds
Cash flows from operating activities:
Cash flows due to changes in operating assets and liabilities			(34,335)	$ 37,108
ASC 606 | Adjustments
Cash flows from operating activities:
Net income (loss)			3,580
Cash flows due to changes in operating assets and liabilities			(1,720)
ASC 606 | Balances without adoption of ASC 606
Cash flows from operating activities:
Net income (loss)			92,170
Cash flows due to changes in operating assets and liabilities			65,205
ASC 606 | Consolidated Funds | Adjustments
Cash flows from operating activities:
Cash flows due to changes in operating assets and liabilities			(1,860)
ASC 606 | Consolidated Funds | Balances without adoption of ASC 606
Cash flows from operating activities:
Cash flows due to changes in operating assets and liabilities			$ (36,195)