DEBT - NARRATIVE (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 CAD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 CAD ($)
Line of Credit Facility [Line Items]
Commitment fee percentage	0.20%	0.20%
Long-term debt	$ 61,191,000,000		$ 60,865,000,000
Uncommitted demand credit facilities
Line of Credit Facility [Line Items]
Amount of credit facility	790,000,000		792,000,000
Unutilized amount of facility	511,000,000		518,000,000
Commercial paper and credit facility draws
Line of Credit Facility [Line Items]
Long-term debt	9,832,000,000		$ 10,055,000,000
Enbridge (U.S.) Inc.
Line of Credit Facility [Line Items]
Extinguishment of debt		$ 950
Westcoast Energy Inc
Line of Credit Facility [Line Items]
Extinguishment of debt	$ 400,000,000
Enbridge Inc.
Line of Credit Facility [Line Items]
Extinguishment of debt		$ 650