Segment Disclosures Recon from Segment to Consolidated - Revenues (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment revenues [Line Items]
Revenues	$ 7,719	$ 8,201	$ 8,686
Other financial information:
Additions to long-lived assets	1,283	2,911	3,171
Proportional Modified EBITDA Equity Method Investments	749	746	770
Intersegment Eliminations [Member]
Segment revenues [Line Items]
Revenues	(256)	(280)	(488)
Other financial information:
Additions to long-lived assets	0	0	0
Proportional Modified EBITDA Equity Method Investments	0	0	0
Operating Segments [Member] | Transmission And Gulf Of Mexico [Member]
Segment revenues [Line Items]
Revenues	3,469	3,640	3,447
Other financial information:
Additions to long-lived assets	706	1,341	2,379
Proportional Modified EBITDA Equity Method Investments	166	177	183
Operating Segments [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenues	1,529	1,500	1,283
Other financial information:
Additions to long-lived assets	137	1,245	477
Proportional Modified EBITDA Equity Method Investments	473	454	493
Operating Segments [Member] | West [Member]
Segment revenues [Line Items]
Revenues	2,943	3,311	4,410
Other financial information:
Additions to long-lived assets	318	304	279
Proportional Modified EBITDA Equity Method Investments	110	115	94
Operating Segments [Member] | Other [Member]
Segment revenues [Line Items]
Revenues	34	30	34
Other financial information:
Additions to long-lived assets	122	21	36
Proportional Modified EBITDA Equity Method Investments	0	0	0
Service [Member]
Segment revenues [Line Items]
Revenues	5,924	5,933	5,502
Service [Member] | Transmission And Gulf Of Mexico [Member]
Segment revenues [Line Items]
Revenues	3,207	3,261	2,904
Service [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenues	1,416	1,291	935
Service [Member] | West [Member]
Segment revenues [Line Items]
Revenues	1,280	1,364	1,641
Service [Member] | Other [Member]
Segment revenues [Line Items]
Revenues	21	17	22
Service [Member] | Intersegment Eliminations [Member]
Segment revenues [Line Items]
Revenues	(112)	(110)	(102)
Service [Member] | Intersegment Eliminations [Member] | Transmission And Gulf Of Mexico [Member]
Segment revenues [Line Items]
Revenues	(50)	(50)	(49)
Service [Member] | Intersegment Eliminations [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenues	(49)	(47)	(41)
Service [Member] | Intersegment Eliminations [Member] | West [Member]
Segment revenues [Line Items]
Revenues	0	0	0
Service [Member] | Intersegment Eliminations [Member] | Other [Member]
Segment revenues [Line Items]
Revenues	(13)	(13)	(12)
Service [Member] | Operating Segments [Member] | Transmission And Gulf Of Mexico [Member]
Segment revenues [Line Items]
Revenues	3,257	3,311	2,953
Service [Member] | Operating Segments [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenues	1,465	1,338	976
Service [Member] | Operating Segments [Member] | West [Member]
Segment revenues [Line Items]
Revenues	1,280	1,364	1,641
Service [Member] | Operating Segments [Member] | Other [Member]
Segment revenues [Line Items]
Revenues	34	30	34
NonRegulated Service Commodity Consideration [Member]
Segment revenues [Line Items]
Revenues	129	203	400
NonRegulated Service Commodity Consideration [Member] | Intersegment Eliminations [Member]
Segment revenues [Line Items]
Revenues	0	0	0
NonRegulated Service Commodity Consideration [Member] | Operating Segments [Member] | Transmission And Gulf Of Mexico [Member]
Segment revenues [Line Items]
Revenues	21	41	59
NonRegulated Service Commodity Consideration [Member] | Operating Segments [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenues	7	12	20
NonRegulated Service Commodity Consideration [Member] | Operating Segments [Member] | West [Member]
Segment revenues [Line Items]
Revenues	101	150	321
NonRegulated Service Commodity Consideration [Member] | Operating Segments [Member] | Other [Member]
Segment revenues [Line Items]
Revenues	0	0	0
Product [Member]
Segment revenues [Line Items]
Revenues	1,666	2,065	2,784
Product [Member] | Transmission And Gulf Of Mexico [Member]
Segment revenues [Line Items]
Revenues	144	217	174
Product [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenues	16	115	245
Product [Member] | West [Member]
Segment revenues [Line Items]
Revenues	1,506	1,733	2,365
Product [Member] | Other [Member]
Segment revenues [Line Items]
Revenues	0	0	0
Product [Member] | Intersegment Eliminations [Member]
Segment revenues [Line Items]
Revenues	(144)	(170)	(386)
Product [Member] | Intersegment Eliminations [Member] | Transmission And Gulf Of Mexico [Member]
Segment revenues [Line Items]
Revenues	(47)	(71)	(261)
Product [Member] | Intersegment Eliminations [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenues	(41)	(35)	(42)
Product [Member] | Intersegment Eliminations [Member] | West [Member]
Segment revenues [Line Items]
Revenues	(56)	(64)	(83)
Product [Member] | Intersegment Eliminations [Member] | Other [Member]
Segment revenues [Line Items]
Revenues	0	0	0
Product [Member] | Operating Segments [Member] | Transmission And Gulf Of Mexico [Member]
Segment revenues [Line Items]
Revenues	191	288	435
Product [Member] | Operating Segments [Member] | Northeast G And P [Member]
Segment revenues [Line Items]
Revenues	57	150	287
Product [Member] | Operating Segments [Member] | West [Member]
Segment revenues [Line Items]
Revenues	1,562	1,797	2,448
Product [Member] | Operating Segments [Member] | Other [Member]
Segment revenues [Line Items]
Revenues	$ 0	$ 0	$ 0