INVESTMENTS - Equity-method Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Assets:
Cash and cash-equivalents	$ 3,109,839		$ 3,713,045
Investments, at fair value	42,303,584		43,084,842
Other assets	2,145,832		1,994,304
Total assets	47,559,255		48,792,191
Liabilities and Capital:
Debt obligations	7,650,448		7,372,063
Other liabilities	2,256,633		2,028,065
Total liabilities	9,907,081		9,400,128
Total capital	37,652,174		39,392,063
Total liabilities and capital	47,559,255		$ 48,792,191
Statements of Operations:
Revenues / investment income	520,610	$ 542,834
Interest expense	(47,014)	(38,529)
Other expenses	(211,158)	(220,436)
Net realized and unrealized gain on investments	924,551	288,067
Net income	$ 1,186,989	$ 571,936