Other Income and Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Component Of Other Income [Line Items]
Total other income	$ 18	$ 16
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	29	15
Loss On Sale And Disposal Of Assets [Member]
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	24	10
Other Member
Component Of Operating Other Cost And Expense [Line Items]
Total other expense	$ 5	$ 5