INVESTMENTS - Equity-method Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets:
Cash and cash-equivalents	$ 1,892,353	$ 3,875,072
Investments, at fair value	25,213,422	39,711,382
Other assets	635,277	2,832,960
Total assets	27,741,052	46,419,414
Liabilities and Capital:
Debt obligations	3,558,139	7,234,596
Other liabilities	3,779,527	2,662,850
Total liabilities	7,337,666	9,897,446
Total capital	20,403,386	36,521,968
Total liabilities and capital	27,741,052	46,419,414
Statements of Operations
Revenues / investment income	766,096	1,861,551	$ 1,982,828
Interest expense	(150,078)	(276,779)	(235,266)
Other expenses	(402,814)	(876,627)	(821,083)
Net realized and unrealized gain on investments	1,077,761	1,087,345	3,795,102
Net income	$ 1,290,965	$ 1,795,490	$ 4,721,581