Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current deferred tax asset:
Accrued liabilities	$ 111	$ 23
Valuation allowance	(111)	(23)
Net current deferred tax asset	0	0
Non-current deferred tax assets:
Fixed and intangible assets	11	9
Net operation loss carry-forwards	122,205	121,180
AMT credit carry-forwards	74	74
Capital loss and charitable carry-forwards	13	9
Research and experimental tax credits	11,021	11,021
Stock compensation	586	486
Deferred revenue	22,213	16,621
Interest	6,870	3,414
Valuation allowance	(162,993)	(152,814)
Net non-current deferred tax asset	$ 0	$ 0