Contingencies - Legal Proceedings (Details) CAD in Millions							9 Months Ended
	Sep. 28, 2017 CAD	Jul. 11, 2016 CAD claim	Jul. 05, 2016 CAD	Jul. 04, 2016 CAD claim	Apr. 12, 2016 CAD	Jul. 06, 2015 CAD	Sep. 30, 2017 CAD claim
Claimed loss or damages as a result of derailment [Member]
Commitments and Contingencies Disclosure [Line Items]
Settlement amounts							CAD 440
Lac-Megantic Rail Accident [Member]
Commitments and Contingencies Disclosure [Line Items]
Value of damages sought	CAD 315					CAD 409
Lac-Megantic Rail Accident [Member] | World Fuel Entities [Member]
Commitments and Contingencies Disclosure [Line Items]
Settlement amounts					CAD 110
Lac-Megantic Rail Accident [Member] | Irving Oil [Member]
Commitments and Contingencies Disclosure [Line Items]
Settlement amounts					60
Lac-Megantic Rail Accident [Member] | Quebec Minister of Sustainable Development and Environment [Member]
Commitments and Contingencies Disclosure [Line Items]
Value of damages sought			CAD 95
Lac-Megantic Rail Accident [Member] | Subrogated Insurance Claim [Member] | Initial Insurer Claimants [Member]
Commitments and Contingencies Disclosure [Line Items]
Value of damages sought	CAD 15			CAD 16
Number of notices for claims of damage to cargo | claim				8
Lac-Megantic Rail Accident [Member] | Subrogated Insurance Claim [Member] | Additional Insurer Claimants [Member]
Commitments and Contingencies Disclosure [Line Items]
Value of damages sought		CAD 3
Number of notices for claims of damage to cargo | claim		2
Lac-Megantic Rail Accident [Member] | Claimed loss or damages as a result of derailment [Member]
Commitments and Contingencies Disclosure [Line Items]
Number of notices for claims of damage to cargo | claim							2
Lac-Megantic Rail Accident [Member] | Lost Lading Loss Recovery [Member] | The “WD Trustee” [Member]
Commitments and Contingencies Disclosure [Line Items]
Value of damages sought					CAD 6