AQUISITIONS AND DISPOSITIONS - Narrative (Details) - Dispositions $ in Millions					6 Months Ended
	Jun. 01, 2020 CAD ($)	May 01, 2020 CAD ($)	Apr. 01, 2020 CAD ($)	Apr. 01, 2020 USD ($)	Jun. 30, 2020 CAD ($)	Jun. 30, 2020 USD ($)
Line 10 Crude Oil Pipeline
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposal	$ 0
Montana-Alberta Tie Line Transmission Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposal					$ 4,000,000
Proceeds from dispositions		$ 189,000,000
Ozark assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on disposal					$ 1,000,000	$ 1
Proceeds from dispositions			$ 63,000,000	$ 45