Investment in Kansas City Southern - Summarized Financial Information, Statement of Income (Details) $ in Millions	3 Months Ended	12 Months Ended
	Apr. 13, 2023 CAD ($)	Dec. 31, 2024 CAD ($)	Dec. 31, 2023 CAD ($)	Dec. 31, 2022 CAD ($)
Schedule of Equity Method Investments [Line Items]
Total revenues		$ 14,546	$ 12,555	$ 8,814
Total operating expenses		9,367	8,167	5,485
Operating income		5,179	4,388	3,329
Less: Other		(42)	52	17
Income (loss) before income tax expense (recovery)		4,772	(3,053)	4,145
Net income		$ 3,718	$ 3,927	$ 3,517
Daily exchange rate used, revenue	1.35			1.30
Canada, Dollars
Schedule of Equity Method Investments [Line Items]
Daily exchange rate used, revenue	1.35			1.30
Kansas City Southern
Schedule of Equity Method Investments [Line Items]
Total revenues	$ 1,351			$ 4,390
Total operating expenses	888			2,794
Operating income	463			1,596
Less: Other	83			(119)
Income (loss) before income tax expense (recovery)	380			1,715
Net income	$ 280			$ 1,287