Contingencies - Environmental Liabilities (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Environmental remediation expense	$ 2	$ 1	$ 6	$ 5
Accrued environmental loss contingencies, noncurrent	$ 231		$ 231		$ 83
Term for expected payments to be made			10 years