Other long-term liabilities - Narrative (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Other Liabilities Disclosure [Abstract]
Expected time period for payment of provision for environmental remediation	10 years
Environmental remediation costs charged to income	$ 10	$ 10	$ 6