Net interest expense (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Interest Income (Expense), Net [Abstract]
Interest cost	$ 459	$ 478	$ 471
Interest capitalized to Properties	(13)	(16)	(17)
Interest expense	446	462	454
Interest income	(6)	(4)	(6)
Net interest expense	$ 440	$ 458	$ 448