Other (Income) Expense - Other Income and Expenses (Details) - CAD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Other Income and Expenses [Abstract]
Foreign exchange (gain) loss on debt and lease liabilities	$ (37)	$ 44	$ (82)	$ 93
Other foreign exchange (gains) losses	(4)	4	(6)	3
Other	1	4	1	7
Other expense (income)	$ (40)	$ 52	$ (87)	$ 103