Accounts Payable and Accrued Liabilities (Details) - CAD ($) $ in Millions	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Trade payables	$ 453		$ 474
Accrued charges	348		360
Unearned revenue	142		2
Income and other taxes payable	139		104
Accrued interest	131		135
Dividends payable	114		91
Stock-based compensation liabilities	85		53
Payroll-related accruals	78		78
Operating leases	69		0
Accrued vacation	60		61
Personal injury and other claims provision	55		68
Provision for environmental remediation	7		8
Other(1)	12		15
Total accounts payable and accrued liabilities	$ 1,693	$ 1,507	$ 1,449