Interest 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
Interest Expense
Interest expense	$ 132	$ 149	$ 264	$ 284
Interest income		(1)	(1)	(2)
Interest expense, net	$ 132	$ 148	$ 263	$ 282