Other (Income) Expense - Other Income and Expense (Details) - CAD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other Income and Expenses [Abstract]
Foreign exchange (gain) loss on debt and lease liabilities	$ (52)	$ (86)	$ (85)	$ 129
Other foreign exchange (gains) losses	(3)	1	(2)	(4)
Acquisition-related costs	209	0	212	0
Other	3	(1)	4	0
Other expense (income)	$ 157	$ (86)	$ 129	$ 125