Segment Disclosures Reconciliation of Segment Revenues to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment revenues
Revenues	$ 1,999	$ 2,303	$ 6,094	$ 6,482
Intersegment Elimination [Member]
Segment revenues
Revenues	(58)	(147)	(209)	(365)
Operating Segments [Member] | Northeast G And P [Member]
Segment revenues
Revenues	384	322	1,082	963
Operating Segments [Member] | Atlantic Gulf [Member]
Segment revenues
Revenues	814	756	2,397	2,180
Operating Segments [Member] | West [Member]
Segment revenues
Revenues	852	1,362	2,802	3,678
Operating Segments [Member] | Other [Member]
Segment revenues
Revenues	7	10	22	26
Service [Member]
Segment revenues
Revenues	1,495	1,371	4,424	4,062
Service [Member] | Northeast G And P [Member]
Segment revenues
Revenues	340	236	925	677
Service [Member] | Atlantic Gulf [Member]
Segment revenues
Revenues	718	595	2,102	1,769
Service [Member] | West [Member]
Segment revenues
Revenues	433	533	1,384	1,599
Service [Member] | Other [Member]
Segment revenues
Revenues	4	7	13	17
Service [Member] | Intersegment Elimination [Member]
Segment revenues
Revenues	(29)	(26)	(79)	(76)
Service [Member] | Intersegment Elimination [Member] | Northeast G And P [Member]
Segment revenues
Revenues	(13)	(11)	(34)	(30)
Service [Member] | Intersegment Elimination [Member] | Atlantic Gulf [Member]
Segment revenues
Revenues	(13)	(12)	(36)	(37)
Service [Member] | Intersegment Elimination [Member] | West [Member]
Segment revenues
Revenues	0	0	0	0
Service [Member] | Intersegment Elimination [Member] | Other [Member]
Segment revenues
Revenues	(3)	(3)	(9)	(9)
Service [Member] | Operating Segments [Member] | Northeast G And P [Member]
Segment revenues
Revenues	353	247	959	707
Service [Member] | Operating Segments [Member] | Atlantic Gulf [Member]
Segment revenues
Revenues	731	607	2,138	1,806
Service [Member] | Operating Segments [Member] | West [Member]
Segment revenues
Revenues	433	533	1,384	1,599
Service [Member] | Operating Segments [Member] | Other [Member]
Segment revenues
Revenues	7	10	22	26
NonRegulated Service Commodity Consideration [Member]
Segment revenues
Revenues	38	121	158	316
NonRegulated Service Commodity Consideration [Member] | Intersegment Elimination [Member]
Segment revenues
Revenues	0	0	0	0
NonRegulated Service Commodity Consideration [Member] | Operating Segments [Member] | Northeast G And P [Member]
Segment revenues
Revenues	1	6	9	14
NonRegulated Service Commodity Consideration [Member] | Operating Segments [Member] | Atlantic Gulf [Member]
Segment revenues
Revenues	7	18	33	45
NonRegulated Service Commodity Consideration [Member] | Operating Segments [Member] | West [Member]
Segment revenues
Revenues	30	97	116	257
NonRegulated Service Commodity Consideration [Member] | Operating Segments [Member] | Other [Member]
Segment revenues
Revenues	0	0	0	0
Product [Member]
Segment revenues
Revenues	466	811	1,512	2,104
Product [Member] | Northeast G And P [Member]
Segment revenues
Revenues	22	59	87	214
Product [Member] | Atlantic Gulf [Member]
Segment revenues
Revenues	66	46	169	131
Product [Member] | West [Member]
Segment revenues
Revenues	378	706	1,256	1,759
Product [Member] | Other [Member]
Segment revenues
Revenues	0	0	0	0
Product [Member] | Intersegment Elimination [Member]
Segment revenues
Revenues	(29)	(121)	(130)	(289)
Product [Member] | Intersegment Elimination [Member] | Northeast G And P [Member]
Segment revenues
Revenues	(8)	(10)	(27)	(28)
Product [Member] | Intersegment Elimination [Member] | Atlantic Gulf [Member]
Segment revenues
Revenues	(10)	(85)	(57)	(198)
Product [Member] | Intersegment Elimination [Member] | West [Member]
Segment revenues
Revenues	(11)	(26)	(46)	(63)
Product [Member] | Intersegment Elimination [Member] | Other [Member]
Segment revenues
Revenues	0	0	0	0
Product [Member] | Operating Segments [Member] | Northeast G And P [Member]
Segment revenues
Revenues	30	69	114	242
Product [Member] | Operating Segments [Member] | Atlantic Gulf [Member]
Segment revenues
Revenues	76	131	226	329
Product [Member] | Operating Segments [Member] | West [Member]
Segment revenues
Revenues	389	732	1,302	1,822
Product [Member] | Operating Segments [Member] | Other [Member]
Segment revenues
Revenues	$ 0	$ 0	$ 0	$ 0