Business Segments - Table Narrative (Detail) - CAD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Segment Reporting Information [Line Items]
Revenue from contracts with customers		$ 9,729	$ 10,520
Revenue outside the scope of ASC 606		2,520	1,537
Total	[1]	12,249	12,057
United States Exports
Segment Reporting Information [Line Items]
Operating revenues		$ 2,378	$ 2,375

[1] (a) Amounts from related parties included in revenues.2,729 3,136