Net Income (Loss) Per Share (Detail) - CAD CAD / shares in Units, shares in Millions, CAD in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net income (loss) per common share - basic
Net income (loss)	CAD (181)	CAD 120	CAD (282)	CAD 541
Weighted average number of common shares outstanding (millions of shares)	847.6	847.6	847.6	847.6
Net income (loss) per common share (dollars)	CAD (0.21)	CAD 0.14	CAD (0.33)	CAD 0.64
Net income (loss) per common share - diluted
Net income (loss)	CAD (181)	CAD 120	CAD (282)	CAD 541
Weighted average number of common shares outstanding (millions of shares)	847.6	847.6	847.6	847.6
Effect of share-based awards (millions of shares)	3.0	3.1	2.9	3.0
Weighted average number of common shares outstanding, assuming dilution (millions of shares)	850.6	850.7	850.5	850.6
Net income (loss) per common share (dollars)	CAD (0.21)	CAD 0.14	CAD (0.33)	CAD 0.64

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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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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