PENSION AND OTHER POSTRETIREMENT BENEFITS PENSION AND OTHER POSTRETIREMENT BENEFITS - AMOUNT RECOGNIZED IN EXCESS OF ACCUMULATED OTHER COMPREHENSIVE INCOME (Details) - Pension - CAD CAD in Millions	Dec. 31, 2017	Dec. 31, 2016
Canada
Pension and Other Postretirement Benefit Disclosures
Projected benefit obligations	CAD 1,444	CAD 2,188
Accumulated benefit obligations	1,306	978
Fair value of plan assets	1,131	1,927
United States
Pension and Other Postretirement Benefit Disclosures
Projected benefit obligations	1,280	508
Accumulated benefit obligations	1,217	462
Fair value of plan assets	CAD 1,098	CAD 361

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Amount of accumulated benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2417-114920

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Fair value of plan assets for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

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Amount of projected benefit obligation for defined benefit pension plan with accumulated benefit obligation in excess of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=77993564&loc=d3e4179-114921

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