Income Taxes - Components of Deferred Income Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets, Net [Abstract]
Canadian net operating losses	$ 40,252	$ 35,605
U.S. net operating losses	5,588	3,749
Research and development deductions and credits	9,588	8,234
Other	1,797	1,810
Less: valuation allowance	(57,225)	(49,398)
Net deferred income tax assets	$ 0	$ 0

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from in-process research and development costs expensed in connection with a business combination.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible domestic operating loss carryforwards. Excludes state and local operating loss carryforwards.

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