FAIR VALUE OPTION - Change in Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value, option, assets, net realized gains (losses)	$ 14,066	$ (60,502)	$ (364,288)	$ (494,996)
Fair value, option, liabilities, net realized gains (losses)	(8,460)	13,403	5,172	53,849
Fair value, option, assets, net unrealized gains (losses)	(42,105)	49,195	23,791	259,949
Fair value, option, liabilities, net unrealized gains (losses)	(55,338)	24,483	144,120	(30,490)
Fair value, option, assets, total gains (losses)	(28,039)	(11,307)	(340,497)	(235,047)
Fair value, option, liabilities, total gains (losses)	(63,798)	37,886	149,292	23,359
Private Equity
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value, option, assets, net realized gains (losses)	0	2,981	(4,907)	3,670
Fair value, option, assets, net unrealized gains (losses)	37	(6,692)	5,390	33,803
Fair value, option, assets, total gains (losses)	37	(3,711)	483	37,473
Credit
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value, option, assets, net realized gains (losses)	(2,772)	6,878	(155,879)	(401,720)
Fair value, option, assets, net unrealized gains (losses)	(119,019)	(10,835)	(137,806)	74,003
Fair value, option, assets, total gains (losses)	(121,791)	(3,957)	(293,685)	(327,717)
Investments of Consolidated CFEs
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value, option, assets, net realized gains (losses)	(1,132)	(83,797)	(79,184)	(88,677)
Fair value, option, assets, net unrealized gains (losses)	70,963	43,905	(13,954)	71,952
Fair value, option, assets, total gains (losses)	69,831	(39,892)	(93,138)	(16,725)
Real Assets
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value, option, assets, net realized gains (losses)	5,370	12,611	8,774	12,425
Fair value, option, assets, net unrealized gains (losses)	(5,114)	10,498	4,070	58,108
Fair value, option, assets, total gains (losses)	256	23,109	12,844	70,533
Equity Method - Other
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value, option, assets, net realized gains (losses)	15,062	6,282	(121,514)	6,908
Fair value, option, assets, net unrealized gains (losses)	18,696	(29)	177,385	(3,075)
Fair value, option, assets, total gains (losses)	33,758	6,253	55,871	3,833
Other Investments
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value, option, assets, net realized gains (losses)	(2,462)	(5,457)	(11,578)	(27,602)
Fair value, option, assets, net unrealized gains (losses)	(7,668)	12,348	(11,294)	25,158
Fair value, option, assets, total gains (losses)	(10,130)	6,891	(22,872)	(2,444)
Debt Obligations of Consolidated CFEs
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value, option, liabilities, net realized gains (losses)	(8,460)	13,403	5,172	53,849
Fair value, option, liabilities, net unrealized gains (losses)	(55,338)	24,483	144,120	(30,490)
Fair value, option, liabilities, total gains (losses)	$ (63,798)	$ 37,886	$ 149,292	$ 23,359