Business Segments - Table Narrative (Detail) - CAD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Revenue from contracts with customers		$ 10,520	$ 10,864
Revenue outside the scope of ASC 606		1,537	1,793
Revenues	[1]	12,057	12,657
Downstream
Segment Reporting Information [Line Items]
Revenues		11,639	12,191
United States Exports
Segment Reporting Information [Line Items]
Operating revenues		$ 2,375	$ 2,504

[1] (a) Amounts from related parties included in revenues3,136 3,959