EBP Asset rollforward and B.S. classification (Details 1) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	$ 1,293	$ 1,241
Actual return on plan assets	(11)	78
Employer contributions	65	63
Plan participants' contributions	0	0
Benefits paid	(101)	(86)
Settlements	(5)	(3)
Fair value of plan asets at end of year	1,241	1,293
Funded status - underfunded	(223)	(251)
Accumulated benefit obligation	1,432	1,516
Underfunded/overfunded status of our pension plans and other postretirement benefit plans
Current liabilities	(2)	(2)
Noncurrent liabilities	(221)	(249)
Amounts included in accumulated other comprehensive income (loss):
Prior service credit	0	0
Net actuarial loss	(544)	(593)
Other Postretirement Benefits [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	208	201
Actual return on plan assets	(1)	13
Employer contributions	5	6
Plan participants' contributions	2	2
Benefits paid	(13)	(14)
Settlements	0	0
Fair value of plan asets at end of year	201	208
Funded status - underfunded	(1)	(25)
Underfunded/overfunded status of our pension plans and other postretirement benefit plans
Current liabilities	(7)	(7)
Noncurrent liabilities		(18)
Noncurrent assets	6
Amounts included in accumulated other comprehensive income (loss):
Prior service credit	11	17
Net actuarial loss	(18)	(28)
Amounts included in regulatory liabilities associated with Transco and Northwest Pipeline
Prior service credit	19	30
Net actuarial gain (loss)	6	(4)
Net regulatory assets (liabilities)	$ (78)	$ (62)