Gain on sale of equity investment (Details) $ in Millions, $ in Millions		3 Months Ended			6 Months Ended
	Apr. 01, 2025 USD ($)	Jun. 30, 2025 CAD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2024 CAD ($)	Jun. 30, 2025 CAD ($)	Jun. 30, 2024 CAD ($)
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of equity method investments		$ 493		$ 0	$ 493	$ 0
Gain on sale of equity investment		333		$ 0	333	$ 0
Panama Canal Railway Company
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage sold	50.00%
Equity method investments, Gross sale amount	$ 350
Proceeds from sale of equity method investments		493	$ 344
Gain on sale of equity investment		333	232		$ 333
Equity method investment, realized gain on disposal, after tax		$ 282	$ 196