Accounts Payable and Accrued Liabilities (Details) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Trade payables	$ 401	$ 453
Accrued charges	294	348
Accrued interest	134	131
Dividends payable	127	114
Stock-based compensation liabilities	121	85
Income and other taxes payable	115	139
Payroll-related accruals	68	78
Accrued vacation	59	60
Personal injury and other claims provision	37	55
Deferred revenue	27	142
Deferred real estate lease and license revenue	11	10
Provision for environmental remediation	9	7
Other(1)	1	2
Accounts payable and accrued liabilities	$ 1,467	$ 1,693