Investment in KCS - Summarized Financial Information, Statement of Income (Details) - CAD ($) $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Total revenues		$ 2,040	$ 1,942	$ 2,054	$ 1,959	$ 2,012	$ 1,863	$ 1,792	$ 2,043	$ 7,995	$ 7,710	$ 7,792
Total operating expenses										4,789	4,399	4,668
Operating income		832	774	820	780	928	779	770	834	3,206	3,311	3,124
Other										237	(7)	(89)
Income before income tax expense										3,620	3,202	3,146
Net loss		$ 532	$ 472	$ 1,246	$ 602	$ 802	$ 598	$ 635	$ 409	$ 2,852	$ 2,444	$ 2,440
Kansas City Southern
Schedule of Equity Method Investments [Line Items]
Total revenues	$ 178
Total operating expenses	287
Operating income	(109)
Other	12
Income before income tax expense	(121)
Net loss	$ (106)