Other Assets (Details) - CAD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Long-term materials	$ 26	$ 24
Contracted customer incentives	11	11
Prepaid leases	10	5
Other	24	29
Total other assets	$ 71	$ 69