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East Tank Farm Development (ETFD) (Details) - East Tank Farm Development - CAD
CAD in Millions
12 Months Ended
Nov. 22, 2017
Dec. 31, 2017
EAST TANK FARM DEVELOPMENT PARTNERSHIP (ETFD)    
Gross proceeds CAD 503.0  
Ownership interest (as percent) 51.00%  
Distributions to partners   CAD 25.0
Allocated to interest expense   5.0
Allocated to principal   CAD 20.0
Fort McKay First Nation and the Mikisew Cree First Nation    
EAST TANK FARM DEVELOPMENT PARTNERSHIP (ETFD)    
Ownership interest sold 49.00%