Contingencies - Environmental Liabilities (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Environmental remediation expense	$ 1	$ 2	$ 5	$ 6
Total amount provided for provisions for environmental remediation costs	$ 85		$ 85		$ 79
Term for expected payments to be made			10 years