Lines of Credit and Financing Arrangements (Outstanding Debt Obligations) (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Current maturities of long-term debt:
Finance lease obligations	$ 8,500,000	$ 7,800,000
Debt issuance costs	(900,000)	(900,000)
Total current maturities of long-term debt	343,600,000	321,900,000
Long-Term Debt:
Finance lease obligations	26,300,000	25,900,000
Debt issuance costs	(1,600,000)	(2,100,000)
Total long-term debt	1,047,200,000	849,300,000
Total debt	1,390,800,000	1,171,200,000
Domestic Credit Facility [Member]
Current maturities of long-term debt:
Domestic credit facility and senior unsecured notes	30,000,000.0	30,000,000.0
Long-Term Debt:
Domestic credit facility and senior unsecured notes	672,500,000	475,500,000
Asset Securitization [Member]
Current maturities of long-term debt:
Domestic credit facility and senior unsecured notes	306,000,000.0	285,000,000.0
Senior Unsecured Notes [Member]
Long-Term Debt:
Domestic credit facility and senior unsecured notes	350,000,000.0	350,000,000.0
Foreign Obligations [Member]
Long-Term Debt:
Short-term Debt	$ 0	$ 0