Other Income and Expense - Other Income (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 Other Income [Line Items]
Total other income	$ 13	$ 14	$ 81	$ 32
Contract Termination [Member]
Component Of Other Income [Line Items]
Total other income	0	0	60	0
Gain on sale of assets [Member]
Component Of Other Income [Line Items]
Total other income	4	1	5	3
Other Income Other [Member]
Component Of Other Income [Line Items]
Total other income	$ 9	$ 13	$ 16	$ 29