Other Income and Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Component Of Other Income [Line Items]
Total other income	$ 68	$ 18
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	75	28
Loss On Sale And Disposal Of Assets [Member]
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	15	24
Loss On Extinguishment Of Debt [Member]
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	47	0
Contract termination
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	7	0
Other Member
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	6	4
Contract termination
Component Of Other Income [Line Items]
Total other income	60	0
Gain on sale of assets
Component Of Other Income [Line Items]
Total other income	1	2
Other Income Other [Member]
Component Of Other Income [Line Items]
Total other income	$ 7	$ 16