DEBT - Schedule of Interest Expense (Details) - CAD CAD in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
DEBT
Capitalized	CAD (391)	CAD (321)	CAD (353)
Total interest expense	2,556	1,590	1,624
Spectra Energy
DEBT
Amortization of fair value adjustment - Spectra Energy acquisition	(270)	0	0
Debentures and term notes
DEBT
Interest expense on debt	3,011	1,714	1,805
Commercial paper and credit facility draws
DEBT
Interest expense on debt	CAD 206	CAD 197	CAD 172

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Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
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-Publisher FASB
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-Topic 835
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Amount of interest costs capitalized disclosed as an adjusting item to interest costs incurred.

+ References

No definition available.

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Total interest costs incurred during the period and either capitalized or charged against earnings.

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Amount of the cost of borrowed funds accounted for as interest expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

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