Accounts Payable and Accrued Liabilities (Details) - CAD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Trade payables	$ 474	$ 402
Accrued charges	360	256
Income and other taxes payable	104	72
Accrued interest	135	128
Dividends payable	91	82
Payroll-related accruals	78	72
Accrued vacation	61	59
Stock-based compensation liabilities	53	32
Estimated Litigation Liability, Current	68	28
Provision for environmental remediation	8	8
Financial derivative liability	0	55
Other	17	44
Total accounts payable and accrued liabilities	$ 1,449	$ 1,238