SEGMENTED INFORMATION (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segmented Information
Revenues	$ 9,110	$ 11,598	$ 29,079	$ 37,717
Commodity and gas distribution costs	(4,526)	(7,320)	(15,652)	(23,533)
Operating and administrative	(1,554)	(1,741)	(4,955)	(5,061)
Impairment of long-lived assets	0	(105)	0	(105)
Income/(loss) from equity investments	315	333	805	1,159
Impairment of equity investments	(615)	0	(2,351)	0
Other income/(expense)	258	38	(265)	503
Earnings/(loss) before interest, income taxes, and depreciation and amortization	2,988	2,803	6,661	10,680
Depreciation and amortization	(935)	(844)	(2,766)	(2,526)
Interest expense	(718)	(644)	(2,105)	(1,966)
Income tax expense	(231)	(255)	(273)	(1,275)
Earnings	1,104	1,060	1,517	4,913
Capital expenditures	1,457	1,159	3,836	3,972
Intersegment Eliminations
Segmented Information
Revenues	(168)	(100)	(473)	(362)
Commodity and gas distribution costs	179	111	451	359
Operating and administrative	4	(35)	(143)	(24)
Impairment of long-lived assets		0		0
Income/(loss) from equity investments	0	(1)	0	0
Impairment of equity investments	0		0
Other income/(expense)	192	(15)	(333)	342
Earnings/(loss) before interest, income taxes, and depreciation and amortization	207	(40)	(498)	315
Capital expenditures	22	32	63	71
Liquids Pipelines | Business segments
Segmented Information
Revenues	2,773	2,268	7,252	7,495
Commodity and gas distribution costs	(5)	(12)	(13)	(25)
Operating and administrative	(811)	(815)	(2,458)	(2,392)
Impairment of long-lived assets		0		0
Income/(loss) from equity investments	118	205	463	606
Impairment of equity investments	0		0
Other income/(expense)	15	0	36	26
Earnings/(loss) before interest, income taxes, and depreciation and amortization	2,090	1,646	5,280	5,710
Capital expenditures	442	442	1,503	1,984
Gas Transmission and Midstream | Business segments
Segmented Information
Revenues	1,162	1,264	3,722	3,870
Commodity and gas distribution costs	0	0	0	0
Operating and administrative	(432)	(550)	(1,377)	(1,626)
Impairment of long-lived assets		(105)		(105)
Income/(loss) from equity investments	191	135	284	525
Impairment of equity investments	(615)		(2,351)
Other income/(expense)	28	28	(48)	69
Earnings/(loss) before interest, income taxes, and depreciation and amortization	334	772	230	2,733
Capital expenditures	642	436	1,462	1,254
Gas Distribution and Storage | Business segments
Segmented Information
Revenues	621	635	3,206	3,803
Commodity and gas distribution costs	(87)	(132)	(1,213)	(1,740)
Operating and administrative	(243)	(267)	(761)	(829)
Impairment of long-lived assets		0		0
Income/(loss) from equity investments	(13)	(11)	2	2
Impairment of equity investments	0		0
Other income/(expense)	20	27	51	68
Earnings/(loss) before interest, income taxes, and depreciation and amortization	298	252	1,285	1,304
Capital expenditures	339	247	765	643
Renewable Power Generation and Transmission | Business segments
Segmented Information
Revenues	126	128	429	417
Commodity and gas distribution costs	0	0	0	(2)
Operating and administrative	(57)	(55)	(144)	(137)
Impairment of long-lived assets		0		0
Income/(loss) from equity investments	22	5	59	23
Impairment of equity investments	0		0
Other income/(expense)	2	4	32	(1)
Earnings/(loss) before interest, income taxes, and depreciation and amortization	93	82	376	300
Capital expenditures	11	2	41	18
Energy Services | Business segments
Segmented Information
Revenues	4,596	7,403	14,943	22,494
Commodity and gas distribution costs	(4,613)	(7,287)	(14,877)	(22,125)
Operating and administrative	(15)	(19)	(72)	(53)
Impairment of long-lived assets		0		0
Income/(loss) from equity investments	(3)	0	(3)	3
Impairment of equity investments	0		0
Other income/(expense)	1	(6)	(3)	(1)
Earnings/(loss) before interest, income taxes, and depreciation and amortization	(34)	91	(12)	318
Capital expenditures	$ 1	$ 0	$ 2	$ 2