Stock-based compensation - Summary of Total Share Based Liabilities (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based liabilities paid	$ 137	$ 126	$ 86
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based liabilities paid	116	119	76
DSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based liabilities paid	16	1	9
Other
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based liabilities paid	$ 5	$ 6	$ 1