Pension and Other Benefits - Narrative (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Contributions made by the Company	$ 4	$ 9	$ 15	$ 24