STOCK-BASED COMPENSATION - RESTRICTED UNITS (Details) - Restricted stock units $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
The 2004 Plan
Stock-based compensation
Vesting period	4 years
Annual vesting percentage	25.00%
Number of Shares
Non-vested restricted stock units at the beginning of the period (in shares) | shares	87,298
Vested (in shares) | shares	(38,119)
Forfeited (in shares) | shares	(49,179)
Non-vested restricted stock units at the end of the period (in shares) | shares
Weighted Average Grant Date Fair Value Per Share
Non-vested restricted stock units at the beginning of the period (in dollars per share) | $ / shares	$ 12.69
Vested (in dollars per share) | $ / shares	12.69
Forfeited (in dollars per share) | $ / shares	$ 12.69
Non-vested restricted stock units at the end of the period (in dollars per share) | $ / shares
Additional disclosures
Total fair value of awards vested | $	$ 0.5
The 2014 Plan
Stock-based compensation
Vesting period	4 years
Annual vesting percentage	25.00%
Number of Shares
Non-vested restricted stock units at the beginning of the period (in shares) | shares	569,491
Granted (in shares) | shares	1,428,180
Vested (in shares) | shares	(226,433)
Forfeited (in shares) | shares	(605,192)
Non-vested restricted stock units at the end of the period (in shares) | shares	1,166,046
Weighted Average Grant Date Fair Value Per Share
Non-vested restricted stock units at the beginning of the period (in dollars per share) | $ / shares	$ 17.01
Granted (in dollars per share) | $ / shares	11.63
Vested (in dollars per share) | $ / shares	17.06
Forfeited (in dollars per share) | $ / shares	16.46
Non-vested restricted stock units at the end of the period (in dollars per share) | $ / shares	$ 10.69
Weighted Average Remaining Contractual Term
Non-vested restricted stock units at the end of the period	1 year 6 months 4 days
Additional disclosures
Total fair value of awards vested | $	$ 3.9