Segmented and geographic information - Geographic Information (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 14,546	$ 12,555	$ 8,814
Long-lived assets: Properties and Operating lease ROU assets	56,388	52,091
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	6,936	6,651	6,423
Long-lived assets: Properties and Operating lease ROU assets	16,536	15,933
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	4,988	4,257	2,391
Long-lived assets: Properties and Operating lease ROU assets	27,897	25,141
Mexico
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	2,622	1,647	$ 0
Long-lived assets: Properties and Operating lease ROU assets	$ 11,955	$ 11,017