Properties - Capital Leases Included in Properties (Details) - CAD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Finance Leased Assets [Line Items]
Cost	$ 300	$ 310
Accumulated depreciation	134	139
Net book value	166	171
Rolling stock
Finance Leased Assets [Line Items]
Cost	291	302
Accumulated depreciation	133	138
Net book value	158	164
Other
Finance Leased Assets [Line Items]
Cost	9	8
Accumulated depreciation	1	1
Net book value	$ 8	$ 7