Schedule of Unconditional Purchase Obligations (Parenthetical) (Detail) - CAD CAD in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Unrecorded Unconditional Purchase Obligation [Line Items]
Undiscounted obligations mainly pertaining to pipeline throughput agreements	[1]	CAD 636
Total payments under unconditional purchase obligations		125	CAD 112	CAD 95
Imputed interest on commitments		108
Total present value of commitments excluding imputed interest		CAD 528

[1] Undiscounted obligations of $636 million mainly pertain to pipeline throughput agreements. Total payments under unconditional purchase obligations were $125 million (2014 - $112 million, 2013 - $95 million). The present value of these commitments, excluding imputed interest of $108 million, totaled $528 million.