Lines of Credit and Financing Arrangements (Details Textual 1) $ in Millions	1 Months Ended	6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2014	Nov. 30, 2014 USD ($)	Nov. 13, 2014 USD ($)	Nov. 12, 2014 USD ($)
Line of Credit Facility [Line Items]
Maximum securitization as percentage of net pool balance	100.00%	100.00%
Program fee		0.60%
Average floating commercial paper rate	0.80%	0.80%	0.79%
Unused fee		101.00%
Fixed rate of agreement		0.30%
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Borrowings under Domestic Revolving Credit Facility	$ 613.0	$ 613.0
Committed standby letters of credit	24.7	24.7
Available for future borrowings	289.8	289.8
Maximum [Member]
Line of Credit Facility [Line Items]
Maximum securitization, amount	220.0	220.0
Minimum [Member]
Line of Credit Facility [Line Items]
Maximum securitization, amount	180.0	180.0		$ 180.0
Domestic Credit Facility [Member]
Line of Credit Facility [Line Items]
Domestic Revolving Credit Facility					$ 950.0
Domestic Credit Facility [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum increase in borrowings under Domestic Revolving Credit Facility	350.0	$ 350.0
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Domestic Revolving Credit Facility					650.0	$ 650.0
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
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Domestic Revolving Credit Facility	150.0	$ 150.0
Subfacility for Swingline Loans [Member]
Line of Credit Facility [Line Items]
Domestic Revolving Credit Facility	65.0	65.0
Medium-term Notes [Member] | Domestic Credit Facility [Member]
Line of Credit Facility [Line Items]
Face amount of debt	278.0	278.0			$ 300.0
Periodic payments	$ 22.5	$ 7.5