Leases Components of Lease Expense (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 74	$ 83
Short-term lease cost	16	10
Variable lease cost	5	13
Sublease Income	(3)	(3)
Finance Lease Cost
Amortization of right-of-use assets	10	9
Interest on lease liabilities	10	11	$ 11
Total lease costs	$ 112	$ 123