Gains and Losses on Asset Sales (Detail) (CAD) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Investment And Other Income [Line Items]
Proceeds from asset sales	54	61	62	139
Book value of assets sold	3	6	7	55
Gain/(loss) on asset sales, before tax	51	55	55	84
Gain/(loss) on asset sales, after tax	38	46	41	70