Investment in Kansas City Southern - Summarized Financial Information, Statement of Income (Details) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2021 CAD ($)	Apr. 13, 2023 CAD ($)	Dec. 31, 2023 CAD ($)	Dec. 31, 2022 CAD ($)	Dec. 31, 2021 CAD ($)
Schedule of Equity Method Investments [Line Items]
Total revenues			$ 12,555	$ 8,814	$ 7,995
Total operating expenses			8,167	5,485	4,789
Operating income			4,388	3,329	3,206
Less: Other			52	17	237
(Loss) income before income tax (recovery) expense			(3,053)	4,145	3,620
Net income (loss)			$ 3,927	$ 3,517	$ 2,852
Canada, Dollars
Schedule of Equity Method Investments [Line Items]
Daily exchange rate used, revenue	1.28	1.35		1.30
Kansas City Southern
Schedule of Equity Method Investments [Line Items]
Total revenues	$ 178	$ 1,351		$ 4,390
Total operating expenses	287	888		2,794
Operating income	(109)	463		1,596
Less: Other	12	83		(119)
(Loss) income before income tax (recovery) expense	(121)	380		1,715
Net income (loss)	$ (106)	$ 280		$ 1,287