SHAREHOLDERS’ EQUITY SHAREHOLDERS' EQUITY - Redeemable Common Stock Activities (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Total Temporary Equity
Common stock no longer subject to possible redemption due to extinguishment of Puts		$ (9,098)
Redeemable Common Stock
Shares Subject to Redemption
Beginning balance (in shares)	332,088,000	332,088,000	260,144,000
Release of restricted units for common stock subject to possible redemption (in shares)	25,136,000	25,136,000	16,968,000
Stock options exercised for common stock subject to possible redemption (in shares)			54,976,000
Common stock no longer subject to possible redemption due to extinguishment of Puts (in shares)		(357,224,000)
Ending balance (in shares)		0	332,088,000
Total Temporary Equity
Beginning balance	$ 9,053	$ 9,053	$ 4,995
Release of restricted units for common stock subject to possible redemption		(685)	(326)
Stock options exercised for common stock subject to possible redemption			1,388
Deemed dividends related to change in fair value of common stock subject to possible redemption		640	2,344
Common stock no longer subject to possible redemption due to extinguishment of Puts		(9,098)
Ending balance		$ 0	$ 9,053