Sale of Accounts Receivable (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Sale of Accounts Receivable [Abstract]
Maximum amount provided under accounts receivable securitization facility excluded in lines of credit	$ 1,000,000,000
Receivables sold under securitization facility derecognized during the period	1,600,000,000
Cash payments received in exchange for the transfer of accounts receivable	1,000,000,000
Deferred receivables consideration	597,000,000		900,000,000
Proceeds received in cash from transfers of receivables to purchasers	9,800,000,000	355,000,000
Cash collections on deferred consideration	9,800,000,000	355,000,000
Loss on transfer of accounts receivables to purchasers	$ 1,000,000	$ 1,000,000