Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
Net operating losses	$ 36,911	$ 24,219
License fees	5,800	5,122
Stock-based compensation	9,600	4,999
Legal fees	1,933	1,436
Other	1,643	1,249
Total deferred tax assets	55,887	37,025
Valuation allowance	(55,887)	(37,025)
Net deferred tax assets	$ 0	$ 0