Income Taxes - Components of Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Net deferred income tax assets:
Depreciation and amortization	$ 322	$ 472
Accrued expenses and reserves	720	921
Net operating loss carryforwards	20,135	22,194
Capital loss carryforwards		197
Research and development credit carryforwards	2,673	2,700
Stock-based compensation	750	615
Gross deferred tax assets	24,600	27,099
Less: valuation allowance	(24,552)	(26,842)
Net deferred tax assets	$ 48	$ 257