Other (Income) Expense - Other Income and Expense (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Other Income and Expenses [Abstract]
Foreign exchange loss (gain) on debt and lease liabilities	$ 46	$ (40)	$ (39)	$ 89
Other foreign exchange (gains) losses	(7)	2	(9)	(2)
Acquisition-related costs	83	0	295	0
Other	2	2	6	2
Other expense (income)	$ 124	$ (36)	$ 253	$ 89