Lines of Credit and Financing Arrangements (Details Textual 1) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]
Maximum securitization as percentage of net pool balance		100.00%
Program fee	0.60%
Average floating commercial paper rate	0.78%	0.78%
Unused fee	101.00%
Fixed rate of agreement	0.30%
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Domestic Revolving Credit Facility	$ 650,000,000
Borrowings under Domestic Revolving Credit Facility	177,000,000
Committed standby letters of credit	33,500,000
Available for future borrowings	439,500,000
Extended maturity date	Oct. 31, 2016
Maximum increase in borrowings under Domestic Revolving Credit Facility	100,000,000
Maximum [Member]
Line of Credit Facility [Line Items]
Maximum securitization, amount	220,000,000
Minimum [Member]
Line of Credit Facility [Line Items]
Maximum securitization, amount	$ 160,000,000
Revolving Credit Facility [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Indebtedness to adjusted EBITDA ratio	3.5
Revolving Credit Facility [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Cash flow to net interest expense ratio	3.0