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Income taxes - Narrative (Details) - CAD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Income Tax Disclosure [Abstract]    
Deferred tax assets, non-capital operating loss carryforwards $ 40,367  
Non-capital losses for income tax purposes 175,507  
Valuation allowance, amount 391 $ 881
Operating loss carryforwards, not subject to expiration $ 3,399