REGULATORY MATTERS - Operating Cost Capitalization (Narrative) (Details) - CAD CAD in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Costs capitalized to Property, plant and equipment, net \| Enbridge Gas Distribution
Schedule of Capitalization [Line Items]
Net book value of capitalized costs	CAD 118	CAD 125

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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