Schedule II - Valuation And Qualifying Accounts (Details) (Allowance For Doubtful Accounts [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Allowance For Doubtful Accounts [Member]
Balance at beginning of period	$ 23		$ 24		$ 28
Charged to costs and expenses	41		33		37
Deductions	44	[1]	34	[1]	41	[1]
Balance at end of period	$ 20		$ 23		$ 24

[1] Uncollectible accounts charged off, less recoveries.