GOODWILL (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 33,153	$ 34,459
Acquisition	22
Foreign exchange and other	(487)	(1,306)
Goodwill, ending balance	32,688	33,153
Goodwill [Abstract]
Goodwill, gross at end of period	34,300	34,700
Goodwill accumulated impairment	1,600	1,600
Gas Distribution and Storage
Goodwill [Roll Forward]
Goodwill, beginning balance	5,356	5,356
Acquisition	22
Foreign exchange and other	0	0
Goodwill, ending balance	5,378	5,356
Liquids Pipelines
Goodwill [Roll Forward]
Goodwill, beginning balance	7,951	8,324
Acquisition	0
Foreign exchange and other	(123)	(373)
Goodwill, ending balance	7,828	7,951
Gas Transmission and Midstream
Goodwill [Roll Forward]
Goodwill, beginning balance	19,844	20,777
Acquisition	0
Foreign exchange and other	(364)	(933)
Goodwill, ending balance	19,480	19,844
Energy Services
Goodwill [Roll Forward]
Goodwill, beginning balance	2	2
Acquisition	0
Foreign exchange and other	0	0
Goodwill, ending balance	$ 2	$ 2