INCOME TAXES - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of beginning and ending amount of unrecognized tax benefits [Roll Forward]
Balance as of January 1	$ 79	$ 515
Additions for tax positions related to the current year	0	0
Additions for tax positions of prior years	0	0
Reductions of tax positions of prior years	0	(436)
Balance as of December 31	$ 79	$ 79