Valuation and Qualifying Accounts Valuation and Qualifying Accounts (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 162	$ 196	$ 262
Charged to cost and expenses	79	94	113
Charged to other accounts (1)	16	18	20
Deductions (2)	(195)	(146)	(199)
Balance at End of Period	$ 62	$ 162	$ 196