EARNINGS PER SHARE - Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Basic and diluted income (loss)
Net loss, basic	$ (27,520)	$ (17,475)	$ (54,997)	$ (51,263)
Effect of dilutive securities:
Change in fair value of warrants liability		(159)	(24)	(4,740)
Net loss, diluted	$ (27,520)	$ (17,634)	$ (55,021)	$ (56,003)
Shares used in calculating basic net loss per common share	66,110	64,360	65,901	58,258
Effect of dilutive securities:
Warrants to purchase common shares - liability-classified (in shares)		3		104
Shares used in calculating diluted net loss per common share	66,110	64,363	65,901	58,362
Net (loss) income per common share, basic (in dollars per share)	$ (0.42)	$ (0.27)	$ (0.83)	$ (0.88)
Net (loss) income per common share, diluted (in dollars per share)	$ (0.42)	$ (0.27)	$ (0.83)	$ (0.96)