Lines of Credit and Financing Arrangements (Asset Securitization Program) (Details) - USD ($)	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016	Jul. 05, 2016
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)	1.90%	1.66%
Unused fee (as a percent)	102.00%
Fixed rate of agreement (as a percent)	0.33%
Unused fee charged on incremental available amounts (as a percent)	0.05%
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			$ 200,000,000.0
Unused fee charged on incremental amount limit	$ 200,000,000
Maximum [Member]
Line of Credit Facility [Line Items]
Securitization amount			$ 325,000,000.0