PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant and Equipment (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 113,963	$ 112,404
Total accumulated depreciation	(20,240)	(17,864)
Property, plant and equipment, net	$ 93,723	94,540
Pipelines
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	2.50%
Total property, plant and equipment	$ 56,330	51,647
Facilities and equipment
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	2.70%
Total property, plant and equipment	$ 29,287	27,149
Land and right-of-way
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	2.00%
Total property, plant and equipment	$ 2,947	2,614
Gas mains, services and other
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	2.70%
Total property, plant and equipment	$ 12,194	12,088
Storage
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	2.30%
Total property, plant and equipment	$ 2,748	2,730
Wind turbines, solar panels and other
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	4.10%
Total property, plant and equipment	$ 4,914	5,015
Other
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	6.40%
Total property, plant and equipment	$ 1,486	1,463
Under construction
Property, Plant and Equipment [Line Items]
Weighted Average Depreciation Rate (percent)	0.00%
Total property, plant and equipment	$ 4,057	$ 9,698