Valuation and Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 196	$ 262	$ 265
Charged to cost and expenses	94	113	155
Charged to other accounts (1)	18	20	17
Deductions (2)	(146)	(199)	(175)
Balance at End of Period	$ 162	$ 196	$ 262