Valuation And Qualifying Accounts And Reserves (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Trade Accounts Receivable [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	$ 37	$ 40	$ 40
Charged to costs and expense	0	1	4
Charged to other accounts	2	(1)	(1)
Deductions – Write-offs	(2)	(3)	(3)
Balance at end of period	37	37	40
Deferred Tax Assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of period	359	376	391
Charged to costs and expense	56	(19)	(6)
Charged to other accounts	(15)	2	(9)
Deductions – Write-offs	0	0	0
Balance at end of period	$ 400	$ 359	$ 376