Leases - Components of Lease Expense (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Leases [Abstract]
Operating lease cost	$ 94	$ 77	$ 74
Short-term lease cost	29	17	16
Variable lease cost	10	9	5
Sublease income	(1)	(2)	(3)
Finance lease cost
Amortization of ROU assets	10	6	10
Interest on lease liabilities	2	4	10
Total lease costs	$ 144	$ 111	$ 112