STOCK BASED COMPENSATION - Non-vested Options Outstanding and Exercisable (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Balance at the beginning of the period (in shares)	4,182
Stock options granted (in shares)	645	2,733
Stock options cancelled/forfeited (in shares)	(826)
Stock options vested (in shares)	(1,538)
Balance at the end of the period (in shares)	2,463	4,182
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Balance at the beginning of the period (in dollars per share)	$ 0.74
Stock options granted (in dollars per share)	2.36	$ 0.49	$ 1.45
Stock options cancelled/forfeited (in dollars per share)	0.77
Stock options vested (in dollars per share)	0.85
Balance at the end of the period (in dollars per share)	$ 1.08	$ 0.74