Other Income and Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Component Of Other Income [Line Items]
Total other income	$ 7	$ 57	$ 40	$ 107
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	15	76	59	126
Loss On Sale And Disposal Of Assets [Member]
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	13	31	48	57
Loss On Extinguishment Of Debt [Member]
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	0	37	0	52
Other Member
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	2	8	11	17
Tax Credit Settlement [Member]
Component Of Other Income [Line Items]
Total other income	0	31	0	31
Tax Dispute Settlement [Member]
Component Of Other Income [Line Items]
Total other income	0	14	0	14
Gain on sale of assets
Component Of Other Income [Line Items]
Total other income	2	9	5	25
Insurance Proceeds [Member]
Component Of Other Income [Line Items]
Total other income	0	0	10	0
Other Income Other [Member]
Component Of Other Income [Line Items]
Total other income	$ 5	$ 3	$ 25	$ 37