Commitments and contingencies (Details) $ in Millions, $ in Millions, $ in Millions				12 Months Ended
	Jan. 05, 2024 USD ($)	Aug. 30, 2023 CAD ($)	Oct. 20, 2022 CAD ($)	Dec. 31, 2023 CAD ($) claim plaintiff	Dec. 31, 2023 USD ($) claim plaintiff	Dec. 31, 2023 MXN ($) claim plaintiff	Sep. 30, 2023 CAD ($)
Lytton B.C wildfire & B.C Fraser canyon flooding
Commitments and Contingencies [Line Items]
Former gain contingency, recognized in current period							$ 51
Foreign Tax Authority | Mexican Tax Authority | Tax Year 2014
Commitments and Contingencies [Line Items]
Income tax examination, estimate of possible loss				$ 475		$ 6,068
WD Trustee | 2021 NCIB Program Announcement
Commitments and Contingencies [Line Items]
Damages awarded, value	$ 3.9
Lac-Megantic Rail Accident | Claimed damages as a result of derailment
Commitments and Contingencies [Line Items]
Amount to be distributed				440
Lac-Megantic Rail Accident | Quebec Minister of Sustainable Development, Environment, Wildlife and Parks
Commitments and Contingencies [Line Items]
Value of damages sought				95
Lac-Megantic Rail Accident | Attorney General of Quebec
Commitments and Contingencies [Line Items]
Value of damages sought				315
Value of damages previously sought				409
Lac-Megantic Rail Accident | Initial Subrogated Insurers | Subrogated insurance claim
Commitments and Contingencies [Line Items]
Value of damages sought				15
Value of damages previously sought				$ 16
Number of subrogated insurer claims | claim				8	8	8
Lac-Megantic Rail Accident | Additional Subrogated Insurers | Subrogated insurance claim
Commitments and Contingencies [Line Items]
Value of damages sought				$ 3
Number of subrogated insurer claims | claim				2	2	2
Lac-Megantic Rail Accident | Class Action Plaintiffs
Commitments and Contingencies [Line Items]
Value of damages sought				$ 5
Number of plaintiffs | plaintiff				48	48	48
Lac-Megantic Rail Accident | MMAR Estate Representative | Damages for loss in business value
Commitments and Contingencies [Line Items]
Value of damages sought					$ 30.0
Lac-Megantic Rail Accident | WD Trustee | Damaged railcars and lost crude recovery
Commitments and Contingencies [Line Items]
Value of damages sought					6.0
Lac-Megantic Rail Accident | WD Trustee | Reimbursement for settlement paid by consignor
Commitments and Contingencies [Line Items]
Value of damages sought					110.0
Lac-Megantic Rail Accident | WD Trustee | Reimbursement for settlement paid by consignee
Commitments and Contingencies [Line Items]
Value of damages sought					$ 60.0
Remington Development Corporation legal claim | Remington Development Corporation | Breach of contract
Commitments and Contingencies [Line Items]
Damages awarded, value		$ 165	$ 164
Total estimated damages, value			$ 217
Capital Expenditures
Commitments and Contingencies [Line Items]
Future committed expenditures				$ 2,300
Operating Expenditures
Commitments and Contingencies [Line Items]
Future committed expenditures				$ 544