INCOME TAXES - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
U.S. federal taxes at statutory tax rate									$ (15,587)	$ (10,239)	$ (11,152)
State taxes, net of federal benefit									(26)	61	12
Change in valuation allowance									12,309	6,662	7,624
Foreign tax rate differential									2,752	2,509	2,530
Warrant revaluation									0	(31)	757
Stock-based compensation									1,775	2,025	1,198
Tax credits									(785)	(627)	(906)
Other									(86)	81	363
Total income tax provision	$ (70)	$ 215	$ 99	$ 108	$ 205	$ 81	$ 135	$ 20	$ 352	$ 441	$ 426