Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred tax assets:
Net operating loss carryforwards	$ 7,037	$ 1,298
Research and development credits	460	384
Accrued expenses	58	63
Stock compensation	218
Deferred expenses		1,295
Other	149	94
Deferred tax assets, gross	7,922	3,134
Valuation allowance	(7,466)	(2,658)	$ (1,534)	$ (1,209)
Total deferred tax assets	456	476
Depreciation	(246)	(230)
Total deferred tax liability	(246)	(230)
Net deferred tax asset (liability)	$ 210	$ 246