Segment Disclosures Recon from Segment to Consolidated - Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 8,604
Sales revenue services commodity consideration	400	$ 0	$ 0
Total revenues	8,686	8,031	7,499
Other financial information:
Additions to long-lived assets	3,171	2,814	2,145
Proportional Modified Ebitda Equity Method Investments	770	795	754
Northeast G And P [Member]
Segment revenues [Line Items]
Sales revenue services commodity consideration	20
Atlantic Gulf [Member]
Segment revenues [Line Items]
Sales revenue services commodity consideration	59
West [Member]
Segment revenues [Line Items]
Sales revenue services commodity consideration	321
Other [Member]
Segment revenues [Line Items]
Sales revenue services commodity consideration	0
Intersegment Eliminations [Member]
Segment revenues [Line Items]
Total revenues	(488)	(518)	(536)
Other financial information:
Additions to long-lived assets	0	0	(1)
Proportional Modified Ebitda Equity Method Investments	0	0	0
Operating Segments [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Total revenues	1,283	1,163	1,032
Other financial information:
Additions to long-lived assets	477	460	223
Proportional Modified Ebitda Equity Method Investments	493	452	357
Operating Segments [Member] | Atlantic Gulf [Member]
Segment revenues [Line Items]
Total revenues	3,003	2,723	2,448
Other financial information:
Additions to long-lived assets	2,297	2,001	1,608
Proportional Modified Ebitda Equity Method Investments	183	264	287
Operating Segments [Member] | West [Member]
Segment revenues [Line Items]
Total revenues	4,854	4,259	3,708
Other financial information:
Additions to long-lived assets	361	321	223
Proportional Modified Ebitda Equity Method Investments	94	79	110
Operating Segments [Member] | Other [Member]
Segment revenues [Line Items]
Total revenues	34	404	847
Other financial information:
Additions to long-lived assets	36	32	92
Proportional Modified Ebitda Equity Method Investments	0	0	0
Service [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5,502	5,312	5,171
Service [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	935	837	836
Service [Member] | Atlantic Gulf [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,460	2,202	1,959
Service [Member] | West [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,085	2,246	2,328
Service [Member] | Other [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	22	27	48
Service [Member] | Intersegment Eliminations [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(102)	(83)	(84)
Sales revenue services commodity consideration	0
Service [Member] | Intersegment Eliminations [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	41	35	34
Service [Member] | Intersegment Eliminations [Member] | Atlantic Gulf [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	49	37	39
Service [Member] | Intersegment Eliminations [Member] | West [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0
Service [Member] | Intersegment Eliminations [Member] | Other [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	12	11	11
Service [Member] | Operating Segments [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	976	872	870
Service [Member] | Operating Segments [Member] | Atlantic Gulf [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,509	2,239	1,998
Service [Member] | Operating Segments [Member] | West [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,085	2,246	2,328
Service [Member] | Operating Segments [Member] | Other [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	34	38	59
Product [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,784	2,719	2,328
Product [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	245	264	134
Product [Member] | Atlantic Gulf [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	174	257	245
Product [Member] | West [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,365	1,840	1,183
Product [Member] | Other [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	358	766
Product [Member] | Intersegment Eliminations [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(386)	(435)	(452)
Product [Member] | Intersegment Eliminations [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	42	27	28
Product [Member] | Intersegment Eliminations [Member] | Atlantic Gulf [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	261	227	205
Product [Member] | Intersegment Eliminations [Member] | West [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	83	173	197
Product [Member] | Intersegment Eliminations [Member] | Other [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	0	8	22
Product [Member] | Operating Segments [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	287	291	162
Product [Member] | Operating Segments [Member] | Atlantic Gulf [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	435	484	450
Product [Member] | Operating Segments [Member] | West [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,448	2,013	1,380
Product [Member] | Operating Segments [Member] | Other [Member]
Segment revenues [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 0	$ 366	$ 788