Employee Benefit Plans (Details 2) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Benefits [Member]
Components of net periodic benefit expense:
Service cost		$ 41	$ 35	$ 32
Interest cost		64	64	62
Expected return on plan assets		(77)	(71)	(61)
Amortization of prior service cost (credit)		1	1	1
Amortization of net actuarial loss		38	35	43
Net actuarial loss from settlements		4	0	0
Amortization of regulatory asset		0	0	1
Net periodic benefit expense		71	64	78
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss):
Net actuarial (gain) loss		220	71	(44)
Prior service credit		0	0	0
Amortization of prior service (cost) credit		(1)	(1)	(1)
Amortization of net actuarial loss and loss from settlements		(42)	(35)	(43)
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss)		177	35	(88)
Total recognized in net periodic benefit expense and other comprehensive income (loss)		248	99	(10)
Amounts included in accumulated other comprehensive loss:
Prior service cost (credit)	1
Net actuarial loss	53
Other Postretirement Benefits [Member]
Components of net periodic benefit expense:
Service cost		2	2	2
Interest cost		15	15	16
Expected return on plan assets		(10)	(9)	(9)
Amortization of prior service cost (credit)		(11)	(14)	(11)
Amortization of net actuarial loss		3	3	3
Net actuarial loss from settlements		0	0	0
Amortization of regulatory asset		1	1	5
Net periodic benefit expense		0	(2)	6
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss):
Net actuarial (gain) loss		21	12	1
Prior service credit		(2)	0	(7)
Amortization of prior service (cost) credit		4	5	4
Amortization of net actuarial loss and loss from settlements		(1)	(1)	0
Other changes in plan assets and benefit obligations recognized in other comprehensive income (loss)		22	16	(2)
Total recognized in net periodic benefit expense and other comprehensive income (loss)		22	14	4
Amounts included in accumulated other comprehensive loss:
Prior service cost (credit)	(3)
Net actuarial loss	3
Amounts included in net regulatory assets associated with our FERC-regulated gas pipelines:
Prior service credit	(4)
Net actuarial loss	$ 7