Lines of Credit and Financing Arrangements (Details Textual 1) (USD $)	12 Months Ended
	Dec. 31, 2012	Nov. 16, 2012	Dec. 31, 2011	Nov. 29, 2010
Lines of Credit and Financing Arrangements (Textual) [Abstract]
Maximum securitization, amount	$ 160,000,000	$ 160,000,000		$ 150,000,000
Maximum securitization as percentage of net pool balance	100.00%
Program fee	0.60%
Average floating commercial paper rate	0.85%		0.91%
Unused fee	102.00%
Fixed rate of agreement	0.30%
Domestic revolving credit facility [Member]
Line of Credit Facility [Line Items]
Domestic Revolving Credit Facility	650,000,000
Borrowings under Domestic Revolving Credit Facility	135,000,000
Committed standby letters of credit	69,900,000
Available for future borrowings	465,100,000
Extended maturity date	Oct. 31, 2016
Maximum increase in borrowings under Domestic Revolving Credit Facility	$ 100,000,000
Indebtedness to Adjusted EBITDA Ratio	3.5
Cash Flow to Net Interest Expense ratio	3