Business Segments (Parenthetical) (Detail) - CAD
CAD in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Segment Reporting Information [Line Items]        
Operating revenues [1],[2] CAD 6,568 [3] CAD 7,111 [3] CAD 17,967 [4] CAD 20,553 [4]
United States Exports        
Segment Reporting Information [Line Items]        
Operating revenues CAD 941 CAD 1,168 CAD 2,704 CAD 3,331
[1] Amounts from related parties included in operating revenues.*
[2] Federal excise tax included in operating revenues.
[3] Included export sales to the United States of $941 million (2015 - $1,168 million). Export sales to the United States were recorded in all operating segments, with the largest effects in the Upstream segment.
[4] Included export sales to the United States of $2,704 million (2015 - $3,331 million). Export sales to the United States were recorded in all operating segments, with the largest effects in the Upstream segment.