PROPERTY, PLANT AND EQUIPMENT - Narrative (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 3,500	$ 3,400	$ 3,000
Impairment loss			423
Access Northeast Project
Property, Plant and Equipment [Line Items]
Impairment loss			$ 105