SEGMENTED INFORMATION (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segmented Information
Revenues	$ 11,598	$ 11,345	$ 37,717	$ 34,816
Commodity and gas distribution costs	(7,320)	(7,017)	(23,533)	(22,037)
Operating and administrative	(1,741)	(1,652)	(5,061)	(4,929)
Impairment of long-lived assets	(105)	(4)	(105)	(1,076)
Impairment of goodwill	0	(1,019)	0	(1,019)
Income/(loss) from equity investments	333	378	1,159	1,076
Other income/(expense)	38	24	503	(110)
Earnings/(loss) before interest, income taxes, and depreciation and amortization	2,803	2,055	10,680	6,721
Depreciation and amortization	(844)	(799)	(2,526)	(2,452)
Interest expense	(644)	(696)	(1,966)	(2,042)
Income tax expense	(255)	(347)	(1,275)	(177)
Earnings	1,060	213	4,913	2,050
Capital expenditures	1,159	1,362	3,972	4,633
Intersegment Eliminations
Segmented Information
Revenues	(100)	(120)	(362)	(390)
Commodity and gas distribution costs	111	121	359	392
Operating and administrative	(35)	(25)	(24)	(182)
Impairment of long-lived assets	0	0	0	(5)
Impairment of goodwill		0		0
Income/(loss) from equity investments	(1)	0	0	0
Other income/(expense)	(15)	53	342	(183)
Earnings/(loss) before interest, income taxes, and depreciation and amortization	(40)	29	315	(368)
Capital expenditures	32	(19)	71	(11)
Liquids Pipelines | Business segments
Segmented Information
Revenues	2,268	2,529	7,495	6,388
Commodity and gas distribution costs	(12)	(5)	(25)	(14)
Operating and administrative	(815)	(790)	(2,392)	(2,251)
Impairment of long-lived assets	0	0	0	(154)
Impairment of goodwill		0		0
Income/(loss) from equity investments	205	131	606	399
Other income/(expense)	0	10	26	(15)
Earnings/(loss) before interest, income taxes, and depreciation and amortization	1,646	1,875	5,710	4,353
Capital expenditures	442	651	1,984	1,776
Gas Transmission and Midstream | Business segments
Segmented Information
Revenues	1,264	1,528	3,870	5,329
Commodity and gas distribution costs	0	(270)	0	(1,481)
Operating and administrative	(550)	(519)	(1,626)	(1,560)
Impairment of long-lived assets	(105)	0	(105)	(913)
Impairment of goodwill		(1,019)		(1,019)
Income/(loss) from equity investments	135	262	525	699
Other income/(expense)	28	(42)	69	25
Earnings/(loss) before interest, income taxes, and depreciation and amortization	772	(60)	2,733	1,080
Capital expenditures	436	413	1,254	2,105
Gas Distribution | Business segments
Segmented Information
Revenues	635	645	3,803	3,952
Commodity and gas distribution costs	(132)	(137)	(1,740)	(1,969)
Operating and administrative	(267)	(263)	(829)	(782)
Impairment of long-lived assets	0	0	0	0
Impairment of goodwill		0		0
Income/(loss) from equity investments	(11)	(12)	2	(5)
Other income/(expense)	27	23	68	66
Earnings/(loss) before interest, income taxes, and depreciation and amortization	252	256	1,304	1,262
Capital expenditures	247	311	643	733
Renewable Power Generation and Transmission | Business segments
Segmented Information
Revenues	128	117	417	423
Commodity and gas distribution costs	0	0	(2)	0
Operating and administrative	(55)	(38)	(137)	(104)
Impairment of long-lived assets	0	(4)	0	(4)
Impairment of goodwill		0		0
Income/(loss) from equity investments	5	(6)	23	(27)
Other income/(expense)	4	(18)	(1)	(2)
Earnings/(loss) before interest, income taxes, and depreciation and amortization	82	51	300	286
Capital expenditures	2	6	18	30
Energy Services | Business segments
Segmented Information
Revenues	7,403	6,646	22,494	19,114
Commodity and gas distribution costs	(7,287)	(6,726)	(22,125)	(18,965)
Operating and administrative	(19)	(17)	(53)	(50)
Impairment of long-lived assets	0	0	0	0
Impairment of goodwill		0		0
Income/(loss) from equity investments	0	3	3	10
Other income/(expense)	(6)	(2)	(1)	(1)
Earnings/(loss) before interest, income taxes, and depreciation and amortization	91	(96)	318	108
Capital expenditures	$ 0	$ 0	$ 2	$ 0