Investment in KCS - Summarized Financial Information, Statement of Income (Details) - CAD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Schedule of Equity Method Investments [Line Items]
Total revenues	$ (2,202)	$ (2,054)	$ (4,040)	$ (4,013)
Total operating expenses	1,334	1,234	2,637	2,413
Operating income	868	820	1,403	1,600
Income before income tax expense	1,010	1,503	1,685	2,296
Net income	765	$ 1,246	1,355	$ 1,848
KCS
Schedule of Equity Method Investments [Line Items]
Total revenues	(1,079)		(2,065)
Total operating expenses	680		1,297
Operating income	399		768
Other	59		98
Income before income tax expense	340		670
Net income	$ 248		$ 485