EBP Asset rollforward and B.S. classification (Details 1) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	$ 1,227	$ 1,254
Actual return on plan assets	(45)	184
Employer contributions	88	85
Plan participants’ contributions	0	0
Benefits paid	(35)	(35)
Settlements	(103)	(261)
Net increase (decrease) in fair value of plan assets	(95)	(27)
Fair value of plan assets at end of year	1,132	1,227
Funded status — overfunded (underfunded)	(55)	(92)
Accumulated benefit obligation	1,171	1,294
Overfunded/(underfunded) status of our pension plans and other postretirement benefit plans
Current liabilities	(2)	(2)
Noncurrent liabilities	(53)	(90)
Amounts included in Accumulated other comprehensive income (loss):
Net actuarial loss	(347)	(375)
Amounts included in regulatory liabilities associated with Transco and Northwest Pipeline:
Net regulatory liabilities	49	33
Accumulated benefit obligation for pension plans with accumulated benefit obligation in excess of plan assets	367
Plan assets for pension plans with accumulated benefit obligation in excess of plan assets	326
Other Postretirement Benefits [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	227	208
Actual return on plan assets	(7)	25
Employer contributions	5	5
Plan participants’ contributions	2	3
Benefits paid	(13)	(14)
Settlements	0	0
Net increase (decrease) in fair value of plan assets	(13)	19
Fair value of plan assets at end of year	214	227
Funded status — overfunded (underfunded)	28	21
Overfunded/(underfunded) status of our pension plans and other postretirement benefit plans
Current liabilities	(6)	(6)
Noncurrent assets	34	27
Amounts included in Accumulated other comprehensive income (loss):
Net actuarial loss	(12)	(21)
Amounts included in regulatory liabilities associated with Transco and Northwest Pipeline:
Prior service credit	0	2
Net actuarial gain	4	14
Net regulatory liabilities	$ 116	$ 108