STOCK BASED COMPENSATION - Restricted Stock Units (Details) - Restricted Stock Units - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restricted Stock Units
Vesting period	5 years
Restricted Stock Units
Restricted stock units at the beginning of the period (in shares)	165	161
Awarded (in shares)	5	10
Released (in shares)	0	0
Forfeited (in shares)	(5)	(6)
Restricted stock units at the end of the period (in shares)	165	165	161
Weighted-Average Grant Date Fair Value
Restricted stock units at the beginning of the period (in dollars per share)	$ 3.54	$ 3.16
Awarded (in dollars per share)	8.81	11.20
Forfeited (in dollars per share)	11.09	6.00
Restricted stock units at the end of the period (in dollars per share)	$ 3.47	$ 3.54	$ 3.16
Weighted Average Remaining Contractual Life
Restricted stock units	1 year 4 months 6 days	2 years 3 months 29 days	3 years 3 months 18 days
Aggregate Intrinsic Value
Restricted stock units	$ 861	$ 1,158	$ 921
Stock price	$ 5.22	$ 7.02
Vested (in shares)	0	0
First installment
Restricted Stock Units
Vesting (as a percent)	50.00%
Second installment
Restricted Stock Units
Vesting (as a percent)	50.00%