EBP Asset rollforward and B.S. classification (Details 1) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	$ 1,299	$ 1,132
Actual return on plan assets	212	218
Employer contributions	14	63
Plan participants’ contributions	0	0
Benefits paid	(41)	(111)
Settlements	(127)	(3)
Net increase (decrease) in fair value of plan assets	58	167
Fair value of plan assets at end of year	1,357	1,299
Funded status — overfunded (underfunded)	174	62
Accumulated benefit obligation	1,167	1,221
Overfunded/(underfunded) status of our pension plans and other postretirement benefit plans:
Noncurrent assets	203	92
Current liabilities	(3)	(3)
Noncurrent liabilities	(26)	(27)
Plans with a projected benefit obligation in excess of plan assets:
Projected benefit obligation	29	29
Fair value of plan assets	0	0
Plans with an accumulated benefit obligation in excess of plan assets:
Accumulated benefit obligation	25	26
Fair value of plan assets	0	0
Amounts included in Accumulated other comprehensive income (loss):
Net actuarial loss	(101)	(243)
Amounts included in regulatory liabilities associated with Transco and Northwest Pipeline:
Net regulatory liabilities	39	43
Other Postretirement Benefits [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	247	214
Actual return on plan assets	37	38
Employer contributions	6	5
Plan participants’ contributions	2	2
Benefits paid	(14)	(12)
Settlements	0	0
Net increase (decrease) in fair value of plan assets	31	33
Fair value of plan assets at end of year	278	247
Funded status — overfunded (underfunded)	58	32
Overfunded/(underfunded) status of our pension plans and other postretirement benefit plans:
Noncurrent assets	64	38
Current liabilities	(6)	(6)
Amounts included in Accumulated other comprehensive income (loss):
Net actuarial loss	(25)	(21)
Amounts included in regulatory liabilities associated with Transco and Northwest Pipeline:
Net actuarial gain	32	11
Net regulatory liabilities	$ 100	$ 106