Retirement Benefits (Details 8) (Other Postretirement Benefits [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	$ 17	$ 34
Net (Gain) Loss	320	236
Transition Obligation	14	25
Prior Service Cost, Estimated	4
Net (Gain) Loss, Estimated	6
Transition Obligation, Estimated	10
Reclassification adjustments
Amortization of prior service costs	(20)	(20)	(25)
Total change	69	82	103
Accumulated Other Comprehensive Income [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	0	0
Net (Gain) Loss	6	3
Transition Obligation	0	0
Prior Service Cost, Estimated	0
Net (Gain) Loss, Estimated	0
Transition Obligation, Estimated	0
Components of other Comprehensive income, along with the changes in the balance of regulatory assets, related to the other postretirement benefit plans
Beginning Balance	3	5
Net (gain) loss	(3)	(2)
Reclassification adjustments
Total change	3	(2)
Ending Balance	6	3
Regulatory Assets [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	17	34
Net (Gain) Loss	314	233
Transition Obligation	14	25
Prior Service Cost, Estimated	4
Net (Gain) Loss, Estimated	6
Transition Obligation, Estimated	10
Components of other Comprehensive income, along with the changes in the balance of regulatory assets, related to the other postretirement benefit plans
Beginning Balance	292	374
Net (gain) loss	(84)	(60)
Change in prior service costs/transition obligation	(12)	(2)
Reclassification adjustments
Amortization of transition obligation	(10)	(10)
Amortization of prior service costs	(5)	(5)
Amortization of net gain (loss)	(4)	(5)
Total reclassification adjustments	(19)	(20)
Total change	53	(82)
Ending Balance	$ 345	$ 292