Pension and other post-retirement benefits - Effect of One Percent Change in Assumed Health Care Cost Trend Rate (HCCTR) (Detail) CAD in Thousands	12 Months Ended
Dec. 31, 2016 CAD
Compensation and Retirement Disclosure [Abstract]
Effect of a 1 percentage point increase in the HCCTR on year-end benefit obligation	CAD 11,343
Effect of a 1 percentage point increase in the HCCTR on total service and interest cost	1,019
Effect of a 1 percentage point decrease in the HCCTR on, year-end benefit obligation	(9,430)
Effect of a 1 percentage point decrease in the HCCTR on, total service and interest cost	CAD (846)

No definition available.

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- Definition

Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

+ 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 (m)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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- Definition

Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

+ References

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- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits.

+ References

+ Details

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- Definition

The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs.

+ References

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