Segment Disclosures Reconciliation of Segment Revenues to Consolidated (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment revenues [Line Items]
Service revenues	$ 1,346	$ 1,256
Service revenues - commodity consideration	101	0
Product sales	636	727
Total revenues	2,083	1,983
Northeast G&P [Member]
Segment revenues [Line Items]
Service revenues	219	208
Product sales	89	60
Atlantic-Gulf [Member]
Segment revenues [Line Items]
Service revenues	596	527
Product sales	35	69
West [Member]
Segment revenues [Line Items]
Service revenues	531	518
Product sales	512	405
NGL & Petchem Services [Member]
Segment revenues [Line Items]
Service revenues	0	3
Product sales	0	193
Intersegment Eliminations [Member]
Segment revenues [Line Items]
Service revenues	(22)	(18)
Service revenues - commodity consideration	0
Product sales	(85)	(130)
Total revenues	(107)	(148)
Intersegment Eliminations [Member] | Northeast G&P [Member]
Segment revenues [Line Items]
Service revenues	(9)	(9)
Product sales	(9)	(8)
Intersegment Eliminations [Member] | Atlantic-Gulf [Member]
Segment revenues [Line Items]
Service revenues	(13)	(9)
Product sales	(58)	(65)
Intersegment Eliminations [Member] | West [Member]
Segment revenues [Line Items]
Service revenues	0	0
Product sales	(18)	(51)
Intersegment Eliminations [Member] | NGL & Petchem Services [Member]
Segment revenues [Line Items]
Service revenues	0	0
Product sales	0	(6)
Operating Segments [Member] | Northeast G&P [Member]
Segment revenues [Line Items]
Service revenues	228	217
Service revenues - commodity consideration	4
Product sales	98	68
Total revenues	330	285
Operating Segments [Member] | Atlantic-Gulf [Member]
Segment revenues [Line Items]
Service revenues	609	536
Service revenues - commodity consideration	15
Product sales	93	134
Total revenues	717	670
Operating Segments [Member] | West [Member]
Segment revenues [Line Items]
Service revenues	531	518
Service revenues - commodity consideration	82
Product sales	530	456
Total revenues	1,143	974
Operating Segments [Member] | NGL & Petchem Services [Member]
Segment revenues [Line Items]
Service revenues	0	3
Service revenues - commodity consideration	0
Product sales	0	199
Total revenues	$ 0	$ 202