STOCK-BASED COMPENSATION - Summary of Time-based Stock Options (Details) - USD ($) $ / shares in Units, shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Weighted Average Exercise Price Per Share
Aggregate intrinsic value, vested and expected to vest	$ 100,000	$ 200,000
Time-based stock options
Number of Shares Underlying Stock Options
Beginning outstanding balance (in shares)	967
Granted (in shares)	456
Exercised (in shares)	(76)
Canceled or expired (in shares)	(519)
Ending outstanding balance (in shares)	828	967
Weighted Average Exercise Price Per Share
Beginning outstanding balance (in dollars per share)	$ 8.55
Granted (in dollars per share)	7.58
Exercised (in dollars per share)	7.62
Canceled or expired (in dollars per share)	8.46
Ending outstanding balance (in dollars per share)	$ 8.16	$ 8.55
Weighted average remaining contractual life, outstanding	4 years 4 months 9 days	5 years 7 months 17 days
Aggregate intrinsic value, outstanding	$ 2,628,000	$ 16,000
Number of shares underlying stock options, vested and expected to vest (in shares)	734
Weighted average exercise price, vested and expected to vest (in dollars per share)	$ 8.24
Weighted average remaining contractual life, vested and expected to vest	4 years 2 months 12 days
Aggregate intrinsic value, vested and expected to vest	$ 2,273,000
Number of shares underlying stock options, exercisable (in shares)	362
Weighted average exercise price, exercisable (in dollars per share)	$ 8.26
Weighted average remaining contractual life, exercisable	2 years 8 months 15 days
Aggregate intrinsic value, exercisable	$ 887,000