Leases Supplemental Balance Sheet Information (Details) - CAD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease, ROU asset	$ 287	$ 316
Operating lease, ROU asset, location	Other assets	Other assets
Finance lease, ROU asset	$ 166	$ 171
Finance lease, ROU asset, location	Properties	Properties
Operating lease liabilities, current	$ 59	$ 63
Operating lease liabilities, current, location	Accounts payable and accrued liabilities	Accounts payable and accrued liabilities
Finance lease liabilities, current	$ 104	$ 8
Finance lease liabilities, current, location	Long-term debt maturing within one year	Long-term debt maturing within one year
Operating lease liabilities, long-term	$ 224	$ 248
Operating lease liabilities, long-term, location	Other long-term liabilities	Other long-term liabilities
Finance lease liabilities, long-term	$ 36	$ 135
Finance lease liabilities, long-term, location	Long-term debt	Long-term debt