Lines of Credit and Financing Arrangements (Asset Securitization Program) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Maximum securitization as percentage of net pool balance	100.00%
Program fee percentage	0.65%
Average floating commercial paper rate (as a percent)	1.20%	1.06%
Unused fee	102.00%
Fixed rate of agreement (as a percent)	0.33%
Unused fee charged on incremental available amounts (as a percent)	$ 0.0005
Senior Unsecured Notes [Member]
Line of Credit Facility [Line Items]
Minimum principal amount accelerated	75,000,000.0
Minimum [Member]
Line of Credit Facility [Line Items]
Securitization amount	180,000,000
Maximum [Member]
Line of Credit Facility [Line Items]
Securitization amount	$ 220,000,000.0