INVESTMENTS (Equity Method Investments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Net gains related to equity method investments	$ 66,800	$ 57,100	$ 23,800
Statement of Financial Condition
Investments	18,750,627	15,700,483
Total Assets	19,643,303	16,653,014
Total Liabilities	1,387,203	1,230,075
Total Equity	18,256,100	15,422,939
Statement of Operations
Revenue	903,478	1,370,888	759,617
Expenses	(328,285)	(319,059)	(249,945)
Net realized/unrealized gain from investments	2,741,303	1,697,407	211,509
Income tax expense	(47,151)	(33,312)	(38,401)
Net income	3,269,345	2,715,924	682,780
Credit
Statement of Financial Condition
Investments	5,903,009	4,365,460
Total Assets	6,435,364	4,884,680
Total Liabilities	665,680	522,443
Total Equity	5,769,684	4,362,237
Statement of Operations
Revenue	603,682	416,228	313,833
Expenses	(169,086)	(107,465)	(60,389)
Net realized/unrealized gain from investments	41,185	36,316	(118,035)
Income tax expense	(2,700)	(345)	(3,293)
Net income	473,081	344,734	132,116
Private Equity
Statement of Financial Condition
Investments	9,849,829	8,857,500
Total Assets	10,033,790	9,143,070
Total Liabilities	519,349	197,380
Total Equity	9,514,441	8,945,690
Statement of Operations
Revenue	144,829	839,723	350,444
Expenses	(91,803)	(134,573)	(124,216)
Net realized/unrealized gain from investments	2,335,027	1,489,624	243,470
Income tax expense	(31,359)	(27,587)	(22,004)
Net income	2,356,694	2,167,187	447,694
Real Estate
Statement of Financial Condition
Investments	2,997,789	2,477,523
Total Assets	3,174,149	2,625,264
Total Liabilities	202,174	510,252
Total Equity	2,971,975	2,115,012
Statement of Operations
Revenue	154,967	114,937	95,340
Expenses	(67,396)	(77,021)	(65,340)
Net realized/unrealized gain from investments	365,091	171,467	86,074
Income tax expense	(13,092)	(5,380)	(13,104)
Net income	$ 439,570	$ 204,003	$ 102,970