DEBT - NARRATIVE (Details) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2018 CAD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 CAD ($)	Mar. 31, 2018 USD ($)	Jun. 30, 2018 CAD ($)	Dec. 31, 2017 CAD ($)
Line of Credit Facility [Line Items]
Commitment fee percentage					0.20%
Long-term debt	$ 59,940,000,000				$ 59,940,000,000	$ 60,865,000,000
Long-term debt, fair value adjustment					1,015,000,000
Amortization of fair value adjustment	26,000,000				88,000,000
Uncommitted demand credit facilities
Line of Credit Facility [Line Items]
Amount of credit facility	796,000,000				796,000,000	792,000,000
Unutilized amount of facility	517,000,000				517,000,000	518,000,000
Commercial paper and credit facility draws
Line of Credit Facility [Line Items]
Long-term debt	$ 7,862,000,000				$ 7,862,000,000	$ 10,055,000,000
Enbridge (U.S.) Inc.
Line of Credit Facility [Line Items]
Extinguishment of debt		$ 500		$ 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		$ 100		$ 650