INVESTMENTS - Equity-method Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Assets:
Cash and cash-equivalents	$ 3,499,510		$ 3,499,510		$ 3,713,045
Investments, at fair value	40,725,667		40,725,667		43,084,842
Other assets	1,820,104		1,820,104		1,994,304
Total assets	46,045,281		46,045,281		48,792,191
Liabilities and Capital:
Debt obligations	8,203,642		8,203,642		7,372,063
Other liabilities	2,160,821		2,160,821		2,028,065
Total liabilities	10,364,463		10,364,463		9,400,128
Total capital	35,680,818		35,680,818		39,392,063
Total liabilities and capital	46,045,281		46,045,281		$ 48,792,191
Statements of Operations:
Revenues / investment income	557,070	$ 482,265	1,077,680	$ 1,025,099
Interest expense	(57,857)	(41,640)	(104,871)	(80,169)
Other expenses	(201,099)	(217,303)	(412,257)	(437,739)
Net realized and unrealized gain on investments	942,747	550,657	1,867,298	838,724
Net income	$ 1,240,861	$ 773,979	$ 2,427,850	$ 1,345,915