INVESTMENTS - Equity-method Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Schedule of Equity Method Investments [Line Items]
Revenues / investment income	$ 197,281	$ 891,961
Interest expense	(16,170)	(70,857)
Other expenses	(120,974)	(361,900)
Net realized and unrealized gain (loss) on investments	(3,633,708)	1,005,147
Net income (loss)	$ (3,573,571)	$ 1,464,351
Maximum
Schedule of Equity Method Investments [Line Items]
Ownership percentage	2.50%