ASSETS HELD FOR SALE (Details) $ in Millions, $ in Billions	3 Months Ended
	Mar. 31, 2018 CAD ($)	May 09, 2018 USD ($)
Asset Impairment | Disposal Group, Held-for-sale, Not Discontinued Operations | Midcoast Operating L.P.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Provision for loss (gain) on disposal, before income tax	$ 913
Provision for loss (gain) on disposal, net of tax	701
Asset Impairment | Disposal Group, Held-for-sale, Not Discontinued Operations | Line 10 Crude Oil Pipeline
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Provision for loss (gain) on disposal, before income tax	144
Provision for loss (gain) on disposal, net of tax	$ 85
Subsequent Event | Enbridge (U.S.) Inc. | Midcoast Operating L.P.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, consideration		$ 1.1