Other Financial Data (Accounts Receivable, Net) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Other Financial Data [Abstract]
Accounts receivable	$ 1,932	$ 1,911
Less allowance for doubtful accounts	(51)	(45)
Accounts receivable, net	$ 1,881	$ 1,866