Shareholders' Equity - Activities Under Shares Repurchase Program (Detail) - CAD CAD / shares in Units, CAD in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Stockholders' Equity [Abstract]
Stock Repurchased and Retired During Period, Shares	5,127,800	3,058,900	5,127,800	5,233,688
Weighted-average price per share (in dollars per share)	CAD 169.13	CAD 193.10	CAD 169.13	CAD 206.40
Payments for Repurchase of Common Stock	CAD 867	CAD 590	CAD 867	CAD 1,080