Contingencies - Legal Proceedings (Details) - Lac-Megantic Rail Incident $ in Millions								3 Months Ended
	Dec. 28, 2017 CAD ($)	Oct. 10, 2017 CAD ($)	Jul. 11, 2016 CAD ($) claim	Jul. 05, 2016 CAD ($)	Jul. 04, 2016 CAD ($) claim	Apr. 12, 2016 CAD ($)	Jul. 06, 2015 CAD ($)	Mar. 31, 2018 CAD ($)
Claimed damages as a result of derailment
Other Commitments [Line Items]
Amount of fund to be distributed								$ 440
Irving Oil [Member]
Other Commitments [Line Items]
Value of damages sought						$ 60
Quebec Minister of Sustainable Development, Environment, Wildlife and Parks
Other Commitments [Line Items]
Value of damages sought				$ 95
Quebec Attorney General
Other Commitments [Line Items]
Value of damages sought		$ 315					$ 409
Initial Insurer Claimants | Subrogated insurance claim
Other Commitments [Line Items]
Value of damages sought	$ 14				$ 16
Number of subrogated insurers | claim					8
Additional Insurer Claimants | Subrogated insurance claim
Other Commitments [Line Items]
Value of damages sought			$ 3
Number of subrogated insurers | claim			2
The WD Trustee | Damages railcars loss recovery
Other Commitments [Line Items]
Value of damages sought						6
Montreal Maine and Atlantic Railway | World Fuel Entities [Member]
Other Commitments [Line Items]
Value of damages sought						$ 110