SEGMENTED INFORMATION (Details) - CAD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Segmented Information
Revenues	$ 10,745	$ 11,116	$ 23,471	$ 22,262
Commodity and gas distribution costs	(6,699)	(6,918)	(15,020)	(14,483)
Operating and administrative	(1,636)	(1,646)	(3,277)	(3,197)
Asset impairment	(10)	0	(1,072)	0
Income/(loss) from equity investments	363	236	698	472
Other	(14)	179	(134)	214
Earnings/(loss) before interest and income taxes	2,749	2,967	4,666	5,268
Depreciation and amortization	(829)	(868)	(1,653)	(1,540)
Interest expense	(690)	(565)	(1,346)	(1,051)
Income tax recovery/(expense)	97	(293)	170	(491)
Earnings	1,327	1,241	1,837	2,186
Capital expenditures	1,628	2,348	3,271	4,013
Assets	165,436		165,436		$ 162,093
Assets, excluding goodwill from Merger Transaction	165,436		165,436		162,093
Consolidation, Eliminations
Segmented Information
Revenues	(124)	(98)	(270)	(196)
Commodity and gas distribution costs	125	102	271	200
Operating and administrative	(60)	(116)	(157)	(412)
Asset impairment	0		(5)
Income/(loss) from equity investments	0	(4)	0	(4)
Other	(59)	100	(236)	98
Earnings/(loss) before interest and income taxes	(118)	(16)	(397)	(314)
Capital expenditures	2	9	8	68
Assets	3,190		3,190		2,708
Liquids Pipelines | Business segments
Segmented Information
Revenues	1,950	2,243	3,859	4,398
Commodity and gas distribution costs	(5)	(5)	(9)	(8)
Operating and administrative	(714)	(684)	(1,461)	(1,444)
Asset impairment	(10)		(154)
Income/(loss) from equity investments	137	108	268	194
Other	(36)	(5)	(25)	(3)
Earnings/(loss) before interest and income taxes	1,322	1,657	2,478	3,137
Capital expenditures	510	540	1,125	1,194
Assets	65,740		65,740		63,881
Gas Transmission and Midstream | Business segments
Segmented Information
Revenues	1,864	1,954	3,801	3,189
Commodity and gas distribution costs	(591)	(703)	(1,211)	(1,350)
Operating and administrative	(534)	(553)	(1,041)	(807)
Asset impairment	0		(913)
Income/(loss) from equity investments	229	155	437	265
Other	46	79	67	110
Earnings/(loss) before interest and income taxes	1,014	932	1,140	1,407
Capital expenditures	867	1,374	1,692	2,029
Assets	62,693		62,693		60,745
Gas Distribution | Business segments
Segmented Information
Revenues	1,070	1,022	3,307	2,606
Commodity and gas distribution costs	(444)	(452)	(1,832)	(1,498)
Operating and administrative	(271)	(241)	(519)	(430)
Asset impairment	0		0
Income/(loss) from equity investments	(10)	(23)	7	13
Other	25	4	43	6
Earnings/(loss) before interest and income taxes	370	310	1,006	697
Capital expenditures	239	309	422	492
Assets	25,581		25,581		25,956
Green Power and Transmission | Business segments
Segmented Information
Revenues	149	140	306	277
Commodity and gas distribution costs	0	2	0	3
Operating and administrative	(36)	(41)	(66)	(81)
Asset impairment	0		0
Income/(loss) from equity investments	4	0	(21)	2
Other	9	0	16	1
Earnings/(loss) before interest and income taxes	126	101	235	202
Capital expenditures	10	115	24	229
Assets	6,239		6,239		6,289
Energy Services | Business segments
Segmented Information
Revenues	5,836	5,855	12,468	11,988
Commodity and gas distribution costs	(5,784)	(5,862)	(12,239)	(11,830)
Operating and administrative	(21)	(11)	(33)	(23)
Asset impairment	0		0
Income/(loss) from equity investments	3	0	7	2
Other	1	1	1	2
Earnings/(loss) before interest and income taxes	35	(17)	204	139
Capital expenditures	0	$ 1	0	$ 1
Assets	$ 1,993		$ 1,993		$ 2,514