Leases Supplemental Information Related to Leases (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating cash outflows from operating leases	$ 64	$ 74
Operating cash outflows from finance leases	10	10
Financing cash outflows from finance leases	8	8
Right-of-use assets obtained in exchange for operating lease liabilities	36	34
Right-of-use assets obtained in exchange for finance lease liabilities	$ 5	$ 4