Contingencies - Legal Proceedings (Details) - 3 months ended Mar. 31, 2020 - Lac-Megantic Rail Accident $ in Millions, $ in Millions	CAD ($) claim	USD ($) claim
Claimed derailment damages
Other Commitments [Line Items]
Amount of fund distributed	$ 440
Quebec Minister of Sustainable Development, Environment, Wildlife and Parks
Other Commitments [Line Items]
Value of damages sought	95
Attorney General of Quebec
Other Commitments [Line Items]
Value of damages sought	315
Initial value of damages sought	409
Initial Subrogated Insurers \| Subrogated insurance claim
Other Commitments [Line Items]
Value of damages sought	15
Initial value of damages sought	$ 16
Number of subrogated insurer claims \| claim	8	8
Additional Subrogated Insurers \| Subrogated insurance claim
Other Commitments [Line Items]
Value of damages sought	$ 3
Number of subrogated insurer claims \| claim	2	2
Class Action Plaintiffs
Other Commitments [Line Items]
Value of damages sought	$ 5
Number of plaintiffs \| claim	48	48
WD Trustee \| Damaged rail cars and lost crude recovery
Other Commitments [Line Items]
Value of damages sought		$ 6
WD Trustee \| Reimbursement for settlement paid by consignor
Other Commitments [Line Items]
Value of damages sought		110
WD Trustee \| Reimbursement for settlement paid by consignee
Other Commitments [Line Items]
Value of damages sought		$ 60

Amount of fund to be distributed to those claiming derailment damages.

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