INVESTMENTS (Equity Method Investments) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Equity method investments gain (loss)	$ (3,800)	$ 57,400		$ 78,300
Statement of Financial Condition
Investments	21,122,168	25,577,194	$ 21,122,168
Total assets	22,348,509	27,017,756	22,348,509
Total liabilities	2,779,014	4,909,414	2,779,014
Total equity	19,569,495	22,108,342	19,569,495
Statement of Operations
Revenues		1,401,971	1,175,091	903,478
Expenses		(445,061)	(371,586)	(328,285)
Net realized and unrealized gains (losses) from investments		2,061,425	(542,303)	2,741,303
Income tax expense		(30,350)	(27,155)	(47,151)
Net income		2,987,985	234,047	3,269,345
Credit Group
Statement of Financial Condition
Investments	8,210,094	10,937,224	8,210,094
Total assets	8,799,290	11,625,699	8,799,290
Total liabilities	1,542,058	3,416,429	1,542,058
Total equity	7,257,232	8,209,270	7,257,232
Statement of Operations
Revenues		871,168	766,009	603,682
Expenses		(211,984)	(189,432)	(169,086)
Net realized and unrealized gains (losses) from investments		5,040	(67,477)	41,185
Income tax expense		(1,537)	(2,526)	(2,700)
Net income		662,687	506,574	473,081
Private Equity Group
Statement of Financial Condition
Investments	9,574,998	9,700,725	9,574,998
Total assets	9,785,312	10,077,149	9,785,312
Total liabilities	423,687	534,965	423,687
Total equity	9,361,625	9,542,184	9,361,625
Statement of Operations
Revenues		325,529	264,376	144,829
Expenses		(112,610)	(85,801)	(91,803)
Net realized and unrealized gains (losses) from investments		1,674,002	(892,800)	2,335,027
Income tax expense		(27,887)	(20,554)	(31,359)
Net income		1,859,034	(734,779)	2,356,694
Real Estate Group
Statement of Financial Condition
Investments	3,337,076	4,939,245	3,337,076
Total assets	3,763,907	5,314,908	3,763,907
Total liabilities	813,269	958,020	813,269
Total equity	$ 2,950,638	4,356,888	2,950,638
Statement of Operations
Revenues		205,274	144,706	154,967
Expenses		(120,467)	(96,353)	(67,396)
Net realized and unrealized gains (losses) from investments		382,383	417,974	365,091
Income tax expense		(926)	(4,075)	(13,092)
Net income		$ 466,264	$ 462,252	$ 439,570