Properties - Net Properties (Details) - CAD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Cost	$ 61,785	$ 31,680
Accumulated depreciation	10,041	9,295
Net book value	51,744	22,385
Properties	$ 51,744	22,385
Track and roadway
Property, Plant and Equipment [Line Items]
Weighted-average annual depreciation rate	2.80%
Cost	$ 42,597	21,524
Accumulated depreciation	6,811	6,308
Net book value	$ 35,786	15,216
Rolling stock
Property, Plant and Equipment [Line Items]
Weighted-average annual depreciation rate	3.00%
Cost	$ 1,732	1,069
Accumulated depreciation	281	254
Net book value	1,451	815
Land
Property, Plant and Equipment [Line Items]
Cost	3,487	964
Accumulated depreciation	0	0
Net book value	$ 3,487	964
Buildings
Property, Plant and Equipment [Line Items]
Weighted-average annual depreciation rate	3.60%
Cost	$ 8,125	5,085
Accumulated depreciation	1,629	1,523
Net book value	$ 6,496	3,562
Concession land rights
Property, Plant and Equipment [Line Items]
Weighted-average annual depreciation rate	1.40%
Cost	$ 1,779	0
Accumulated depreciation	17	0
Net book value	$ 1,762	0
Other
Property, Plant and Equipment [Line Items]
Weighted-average annual depreciation rate	6.70%
Cost	$ 4,065	3,038
Accumulated depreciation	1,303	1,210
Net book value	2,762	$ 1,828
Concessions
Property, Plant and Equipment [Line Items]
Cost	9,206
Accumulated depreciation	127
Net book value	9,079
Track and roadway
Property, Plant and Equipment [Line Items]
Cost	7,056
Accumulated depreciation	99
Net book value	6,957
Concession land rights
Property, Plant and Equipment [Line Items]
Cost	1,779
Accumulated depreciation	17
Net book value	1,762
Buildings
Property, Plant and Equipment [Line Items]
Cost	230
Accumulated depreciation	7
Net book value	223
Other
Property, Plant and Equipment [Line Items]
Cost	141
Accumulated depreciation	4
Net book value	$ 137