Lines of Credit and Financing Arrangements (Outstanding Debt Obligations) (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020	Nov. 01, 2016
Current maturities of long-term debt:
Finance lease obligations	$ 11,000,000.0	$ 10,100,000
Debt issuance costs	(100,000)	(200,000)
Total current maturities of long-term debt	265,900,000	9,900,000
Long-Term Debt:
Finance lease obligations	30,300,000	29,300,000
Debt issuance costs	(7,400,000)	(8,600,000)
Total long-term debt	977,400,000	970,700,000
Total debt	1,243,300,000	980,600,000
Domestic Credit Facility [Member]
Long-Term Debt:
Domestic credit facility and senior unsecured notes	4,500,000	0
Asset Securitization [Member]
Current maturities of long-term debt:
Domestic credit facility and senior unsecured notes	255,000,000.0	0
Senior Unsecured Notes [Member]
Long-Term Debt:
Domestic credit facility and senior unsecured notes	950,000,000.0	950,000,000.0
Debt Instrument, Interest Rate, Stated Percentage			3.00%
Foreign Obligations [Member]
Long-Term Debt:
Short-term Debt	$ 0	$ 0