Business Segments (Parenthetical) (Detail) - CAD CAD in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014
Segment Reporting Information [Line Items]
Operating revenues	[1],[2]	CAD 7,272	[3]	CAD 9,399	[3]	CAD 13,442	[4]	CAD 18,596	[4]
United States Exports
Segment Reporting Information [Line Items]
Operating revenues		CAD 1,362		CAD 1,370		CAD 2,163		CAD 2,796

[1] Amounts from related parties included in operating revenues 1,017 742 1,655 1,558

[2] Federal excise tax included in operating revenues 387 383 764 753

[3] Included export sales to the United States of $1,362 million (2014 - $1,370 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 $2,163 million (2014 - $2,796 million). Export sales to the United States were recorded in all operating segments, with the largest effects in the Upstream segment