Leases - Components of Lease Expense (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Operating lease cost	$ 111	$ 94	$ 77
Short-term lease cost	19	29	17
Variable lease cost	16	10	9
Sublease income	(2)	(1)	(2)
Finance lease cost
Amortization of ROU assets	11	10	6
Interest on lease liabilities	2	2	4
Total lease costs	$ 157	$ 144	$ 111