Income Taxes - Schedule of Income tax Recovery (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Computed taxes at combined Canadian and U.S. tax rates	(27.90%)	(27.30%)	(27.40%)
Change in tax rate	(3.60%)		0.10%
Non-deductible expenses	2.20%	1.80%	2.00%
Research and development credits	(0.90%)	(3.50%)
Change in valuation allowance	25.40%	28.40%	25.30%
Effect of the U.S. Tax Cuts and Jobs Act	4.60%
Other	0.20%	0.60%
Income tax recovery	0.00%	0.00%	0.00%