Other assets (Details) - CAD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Operating lease ROU assets	$ 287	$ 316
Contracted customer incentives	77	60
Long-term materials	34	37
Other	21	25
Total other assets	$ 419	$ 438