Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 21,482	$ 8,941
Research and development credits	1,923	649
License fee	3,413	3,880
Other	1,649	177
Gross deferred tax assets	28,467	13,647
Valuation allowance	(28,448)	(13,645)
Total deferred tax assets	19	2
Deferred tax liabilities:
Other	10
Total deferred tax liabilities	10
Total net deferred tax assets	$ 9	$ 2