Lines of Credit and Financing Arrangements (Outstanding Debt Obligations) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Nov. 01, 2016	May 31, 2010
Short-Term Debt:
Total short-term debt	$ 900,000	$ 52,400,000
Current maturities of long-term debt:
Capital lease obligations	3,200,000	800,000
Domestic credit facility	32,600,000	200,100,000
Long-Term Debt:
Capital lease obligations	11,900,000	15,000,000
Total long-term debt	970,500,000	615,700,000
Debt Issuance Cost, Gross, Noncurrent	(4,400,000)	(5,300,000)
Total debt	1,004,000,000	868,200,000
Domestic Credit Facility [Member]
Current maturities of long-term debt:
Domestic credit facility	30,000,000	0
Debt Issuance Costs, Gross, Current	(600,000)	(700,000)
Long-Term Debt:
Total long-term debt	337,000,000	256,000,000
Asset Securitization [Member]
Long-Term Debt:
Total long-term debt	276,000,000	0
Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 350,000,000.0	$ 200,000,000.0
Current maturities of long-term debt:
Domestic credit facility	0	200,000,000
Long-Term Debt:
Total long-term debt	350,000,000	350,000,000
Asset Securitization [Member]
Short-Term Debt:
Total short-term debt	0	50,000,000
Foreign Obligations [Member]
Short-Term Debt:
Total short-term debt	$ 900,000	$ 2,400,000