Other Income and Expense (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Component Of Other Income [Line Items]
Total other income	$ 58	$ 17	$ 108	$ 94
Other Income Net Of Tax And NCI				9
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	76	23	131	83
Tax Credit Settlement [Member]
Component Of Other Income [Line Items]
Total other income	31	0	31	0
Tax Dispute Settlement [Member]
Component Of Other Income [Line Items]
Total other income	14	0	14	0
Extinguishment Of Liability [Member]
Component Of Other Income [Line Items]
Total other income	0	0	0	62
Gain on sale of assets
Component Of Other Income [Line Items]
Total other income	9	5	25	7
Other Income Other [Member]
Component Of Other Income [Line Items]
Total other income	4	12	38	25
Loss On Sale And Disposal Of Assets [Member]
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	31	17	60	36
Parent Company | Loss On Extinguishment Of Debt [Member]
Component Of Operating Other Cost And Expense [Line Items]
Total other expense				9
Loss On Extinguishment Of Debt [Member]
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	36	0	52	9
Wind Generation Transaction Costs [Member]
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	0	0	0	22
Other Member
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	$ 9	$ 6	$ 19	$ 16