Accounts Receivable (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Accounts Receivable Details [Abstract]
Allowance for doubtful accounts	$ 5,000,000		$ 5,000,000
Allowance for doubtful accounts - receivables not expected to be collected in one year	14,000,000		16,000,000
Receivables Securitization Facility [Abstract]
Total capacity to transfer undivided interests to investors under the receivables securitization facility	650,000,000
Receivables securitization facility renewal date	2017-07
Receivables securitization facility duration	3 years
Value of the outstanding undivided interest held by investors under the receivables securitization facility	400,000,000		400,000,000
Accounts receivable supporting the undivided interest held by investors	1,200,000,000		1,200,000,000
Cost of the receivables securitization facility - interest expense	$ 1,000,000	$ 1,000,000