SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Condensed Consolidated Statement of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net income (loss)	$ 74,421	$ (156,324)
Cash flows due to changes in operating assets and liabilities	(37,718)	(135,303)
Consolidated Funds
Cash flows from operating activities:
Cash flows due to changes in operating assets and liabilities	(88,592)	$ 100,086
ASC 606 | Adjustments
Cash flows from operating activities:
Net income (loss)	594
Cash flows due to changes in operating assets and liabilities	(2,313)
ASC 606 | Balances without adoption of ASC 606
Cash flows from operating activities:
Net income (loss)	75,015
Cash flows due to changes in operating assets and liabilities	(40,031)
ASC 606 | Consolidated Funds | Adjustments
Cash flows from operating activities:
Cash flows due to changes in operating assets and liabilities	1,719
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	$ (86,873)