Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Period Type:	duration

Investment in Kansas City Southern - Narrative (Details) - CAD ($) $ in Millions	3 Months Ended	12 Months Ended
	Apr. 13, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 14, 2021
Schedule of Equity Method Investments [Line Items]
Equity loss of Kansas City Southern	$ 230	$ 0	$ 230	$ 1,074
Dividend from Kansas City Southern	300	$ 0		1,157
Interest rate hedge, unwinding				212
Kansas City Southern
Schedule of Equity Method Investments [Line Items]
Basis difference					$ 30,000
Equity method investment, foreign currency translation gain (loss)	(578)			2,891
Amortization of basis difference	$ 48			$ 163