INCOME TAXES - Schedule of net deferred liability (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of Deferred Tax Assets and Liabilities [Abstract]
Net operating losses	$ 42,703	$ 38,234
Capital lease obligations	9,096	13,600
Income tax credits	3,647	3,030
Inventory	6,710	8,080
Stock-based compensation	3,249	4,668
Intellectual property agreements	2,420	3,123
Other deferred temporary differences	1,070	3,055
Deferred tax assets	68,895	73,790
Valuation allowance	(58,831)	(55,223)	$ (46,630)	$ (34,952)
Total deferred tax assets, net of valuation allowance	10,064	18,567
Capital lease assets	(7,655)	(11,949)
Intangible assets	(3,406)	(7,472)
Discount on convertible notes	(2,363)	(4,163)
Deferred tax liability	(13,424)	(23,584)
Net deferred tax liability	$ (3,360)	$ (5,017)