Net Income Per Share (Detail) (CAD) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income per common share - basic
Net income	3,785us-gaap_NetIncomeLoss	2,828us-gaap_NetIncomeLoss	3,766us-gaap_NetIncomeLoss
Weighted average number of common shares outstanding (millions of shares)	847.6	847.6	847.7
Net income per common share (dollars)	4.47us-gaap_EarningsPerShareBasic	3.34us-gaap_EarningsPerShareBasic	4.44us-gaap_EarningsPerShareBasic
Net income per common share - diluted
Net income	3,785us-gaap_NetIncomeLoss	2,828us-gaap_NetIncomeLoss	3,766us-gaap_NetIncomeLoss
Weighted average number of common shares outstanding (millions of shares)	847.6	847.6	847.7
Effect of share-based awards (millions of shares)	3.0	3.0	3.4
Weighted average number of common shares outstanding, assuming dilution (millions of shares)	850.6	850.6	851.1
Net income per common share (dollars)	4.45us-gaap_EarningsPerShareDiluted	3.32us-gaap_EarningsPerShareDiluted	4.42us-gaap_EarningsPerShareDiluted

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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