Pensions and Other Benefits - Pension Plan Asset (Detail) - CAD CAD in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Pension Plan Assets by Fair Value [Line Items]
Fair value of fund assets at December 31	CAD 12,300	CAD 11,376
Pension Plans, Defined Benefit [Member]
Schedule of Pension Plan Assets by Fair Value [Line Items]
Projected benefit obligation at December 31	(11,194)	(11,360)	CAD (9,921)
Fair value of fund assets at December 31	12,300	11,376	CAD 10,722
Funded Status	1,106	16
Pension Plans, Defined Benefit [Member] \| Surplus [Member]
Schedule of Pension Plan Assets by Fair Value [Line Items]
Projected benefit obligation at December 31	(10,681)	(10,878)
Fair value of fund assets at December 31	12,082	11,182
Funded Status	1,401	304
Pension Plans, Defined Benefit [Member] \| Accumulated Deficit [Member]
Schedule of Pension Plan Assets by Fair Value [Line Items]
Projected benefit obligation at December 31	(513)	(482)
Fair value of fund assets at December 31	218	194
Funded Status	CAD (295)	CAD (288)

Schedule of Pension Plan Assets by Fair Value [Line Items]

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- Definition

1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Projected Benefit Obligation
-URI http://asc.fasb.org/extlink&oid=6522206

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Accumulated Postretirement Benefit Obligation
-URI http://asc.fasb.org/extlink&oid=6503904

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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 30
-Section 35
-Paragraph 50
-URI http://asc.fasb.org/extlink&oid=29635418&loc=d3e12355-114930

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

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- Definition

The funded status is measured as the difference between the fair value of plan assets and the benefit obligation. Will normally be the same as the net Defined Benefit Plan, Amounts Recognized in Balance Sheet, Total.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=21915240&loc=d3e1703-114919

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