Other Income and Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Component Of Other Income [Line Items]
Total other income	$ 15	$ 34	$ 33	$ 50
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	15	35	44	50
Loss On Sale And Disposal Of Assets [Member]
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	11	16	35	26
Loss On Extinguishment Of Debt [Member]
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	0	15	0	15
Other Member
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	4	4	9	9
Gain on sale of assets
Component Of Other Income [Line Items]
Total other income	1	14	3	16
Other
Component Of Other Income [Line Items]
Total other income	$ 14	$ 20	$ 30	$ 34