Other Income and Expense - Other Expense (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Component of Operating Other Cost and Expense [Line Items]
Total other expense	$ 18	$ 15	$ 46	$ 43
Loss On Sale And Disposal Of Assets [Member]
Component of Operating Other Cost and Expense [Line Items]
Total other expense	10	11	25	35
Contract Termination [Member]
Component of Operating Other Cost and Expense [Line Items]
Total other expense	0	0	7	0
Other Operating Expense [Member]
Component of Operating Other Cost and Expense [Line Items]
Total other expense	$ 8	$ 4	$ 14	$ 8