Investment in KCS - Narrative (Details) - CAD ($)		3 Months Ended			6 Months Ended
	Apr. 13, 2023	Jun. 30, 2023	Apr. 13, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Investment in Kansas City Southern	$ 44,402,000,000	$ 0	$ 44,402,000,000		$ 0		$ 45,091,000,000
Equity earnings of Kansas City Southern		$ (26,000,000)		$ (208,000,000)	$ (230,000,000)	$ (406,000,000)
KCS
Schedule of Equity Method Investments [Line Items]
Equity earnings of Kansas City Southern	(26,000,000)		(230,000,000)	(208,000,000)		(406,000,000)
Dividends received	0		300,000,000	0		334,000,000
Foreign currency translation	41,000,000		578,000,000	608,000,000		694,000,000
Amortization of basis difference	$ 6,000,000		$ 48,000,000	$ (39,000,000)		$ (79,000,000)