Accounts Payable and Accrued Liabilities (Details) - CAD CAD in Millions	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Trade payables	CAD 402	CAD 352
Accrued charges	256	282
Income and other taxes payable	72	146
Accrued interest	128	137
Derivative Liability, Current	55	69
Payroll-related accruals	72	73
Accrued vacation	59	65
Dividends payable	82	73
Personal injury and other claims provision	28	26
Provision for environmental remediation	8	9
Stock-based compensation liabilities	32	40
Other	44	50
Total accounts payable and accrued liabilities	CAD 1,238	CAD 1,322