Employee Benefit Plans (Details 1) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	$ 965	$ 971
Actual return on plan assets	111	0
Employer contributions	79	68
Plan participants' contributions	0	0
Benefits paid	(75)	(66)
Settlements	(9)	(8)
Fair value of plan asets at end of year	1,071	965
Funded status - underfunded	(478)	(476)
Accumulated benefit obligation	1,519	1,415
Underfunded status of our pension plans and other postretirement benefit plans
Current liabilities	3	7
Noncurrent liabilities	475	469
Amounts included in accumulated other comprehensive loss:
Prior service (cost) credit	(1)	(2)
Net actuarial loss	(828)	(835)
Other Postretirement Benefits [Member]
Change in plan assets:
Fair value of plan assets at beginning of year	159	162
Actual return on plan assets	18	(2)
Employer contributions	13	15
Plan participants' contributions	5	6
Benefits paid	(20)	(22)
Settlements	0	0
Fair value of plan asets at end of year	175	159
Funded status - underfunded	(156)	(180)
Underfunded status of our pension plans and other postretirement benefit plans
Current liabilities	8	8
Noncurrent liabilities	148	172
Amounts included in accumulated other comprehensive loss:
Prior service (cost) credit	7	8
Net actuarial loss	(35)	(40)
Amounts included in net regulatory assets associated with our FERC-regulated gas pipelines:
Prior service credit	14	14
Net actuarial loss	$ (67)	$ (85)