PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 117,954	$ 113,963
Total accumulated depreciation	(23,383)	(20,240)
Property, plant and equipment, net	$ 94,571	93,723	$ 94,540
Pipelines
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	2.70%
Total property, plant and equipment	$ 57,391	56,330
Facilities and equipment
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	2.80%
Total property, plant and equipment	$ 30,057	29,287
Land and right-of-way
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	2.10%
Total property, plant and equipment	$ 2,924	2,947
Gas mains, services and other
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	2.70%
Total property, plant and equipment	$ 12,476	12,194
Storage
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	2.40%
Total property, plant and equipment	$ 2,872	2,748
Wind turbines, solar panels and other
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	4.10%
Total property, plant and equipment	$ 4,877	4,914
Other
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	8.10%
Total property, plant and equipment	$ 1,595	1,486
Under construction
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	0.00%
Total property, plant and equipment	$ 5,762	$ 4,057