Segment Disclosures Recon from Modified EBITDA to Net Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of Modified EBITDA to Net Income (Loss)
Modified EBITDA	$ 4,851	$ 4,447	$ 3,388
Accretion expense associated with asset retirement obligations for nonregulated operations	(35)	(33)	(33)
Depreciation and amortization expenses	(1,721)	(1,714)	(1,725)
Impairment of goodwill (Note 18)	(187)	0	0
Equity earnings (losses) (Note 7)	328	375	396
Impairment of equity-method investments (Note 18)	(1,046)	(186)	(32)
Other investing income (loss) – net (Note 7)	8	107	219
Proportional Modified EBITDA Equity Method Investments	(749)	(746)	(770)
Interest Expense	(1,172)	(1,186)	(1,112)
(Provision) benefit for income taxes	(79)	(335)	(138)
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0	(15)	0
Net income (loss)	198	714	193
Intersegment Eliminations [Member]
Reconciliation of Modified EBITDA to Net Income (Loss)
Proportional Modified EBITDA Equity Method Investments	0	0	0
Operating Segments [Member] | Transmission And Gulf Of Mexico [Member]
Reconciliation of Modified EBITDA to Net Income (Loss)
Modified EBITDA	2,379	2,175	2,293
Proportional Modified EBITDA Equity Method Investments	(166)	(177)	(183)
Operating Segments [Member] | Northeast G And P [Member]
Reconciliation of Modified EBITDA to Net Income (Loss)
Modified EBITDA	1,489	1,314	1,086
Proportional Modified EBITDA Equity Method Investments	(473)	(454)	(493)
Operating Segments [Member] | West [Member]
Reconciliation of Modified EBITDA to Net Income (Loss)
Modified EBITDA	998	952	38
Proportional Modified EBITDA Equity Method Investments	(110)	(115)	(94)
Operating Segments [Member] | Other [Member]
Reconciliation of Modified EBITDA to Net Income (Loss)
Modified EBITDA	(15)	6	(29)
Proportional Modified EBITDA Equity Method Investments	$ 0	$ 0	$ 0