Investment in KCS - Summarized Financial Information (Details) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2024 CAD ($)	Sep. 30, 2023 CAD ($)	Apr. 13, 2023 CAD ($)	Sep. 30, 2024 CAD ($)	Sep. 30, 2023 CAD ($)
Schedule of Equity Method Investments [Line Items]
Total revenues	$ 3,549	$ 3,339		$ 10,672	$ 8,779
Total operating expenses	2,346	2,166		7,053	5,833
Operating income	1,203	1,173		3,619	2,946
Income before income taxes	1,099	1,038		3,327	(4,346)
Net income	$ 837	$ 780		$ 2,517	$ 2,904
Daily exchange rate used, revenue			1.35
KCS
Schedule of Equity Method Investments [Line Items]
Total revenues			$ 1,351
Total operating expenses			888
Operating income			463
Less : other			83
Income before income taxes			380
Net income			$ 280