Segmented and geographic information - Geographic Information (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 12,555	$ 8,814	$ 7,995
Long-lived assets: Properties and right of use assets	52,091	22,652
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	6,651	6,423	5,992
Long-lived assets: Properties and right of use assets	15,933	15,208
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	4,257	2,391	2,003
Long-lived assets: Properties and right of use assets	25,141	7,444
Mexico
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	1,647	0	$ 0
Long-lived assets: Properties and right of use assets	$ 11,017	$ 0