Income Taxes - Components of Deferred Income Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets, Net [Abstract]
Canadian net operating losses	$ 24,049	$ 18,282
U.S. net operating losses	3,889	2,499
Research and development deductions and credits	7,331	4,947
Other	1,389	410
Less: valuation allowance	(36,658)	(26,138)
Net deferred income tax assets	$ 0	$ 0