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Borrowing Arrangements (Narrative) (Details) - USD ($)	3 Months Ended
Borrowing Arrangements (Narrative) (Details) - USD ($)	Dec. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Sep. 30, 2020	Jun. 12, 2018
Outstanding letter of credit accrued fees and expenses	$ 1,400,000
Excess availability reduced by outstanding borrowings, outstanding letters of credit and accrued fees and expenses	133.8
Cash and cash equivalents			$ 223,000,000.0	$ 208,900,000
Future maturities of outstanding borrowings
Line of Credit Facility, Remaining Borrowing Capacity	133.8
Outstanding letters of credit	15,000,000.0
Domestic Line of Credit [Member]
Revolving credit facility amount	$ (175,000,000.0)
Line of Credit Facility, Interest Rate at Period End	200.00%
Future maturities of outstanding borrowings
Line of Credit Facility, Maximum Borrowing Capacity	$ 175,000,000.0
Potential increase size of the credit facility by an additional amount	150,000,000.0
Unsecured Debt [Member]
Long-term Debt, Gross					$ 450,000,000
Future maturities of outstanding borrowings
Payments of debt issuance costs		$ 5,500,000
Swing Line Loans [Member]
Revolving credit facility amount	(25,000,000.0)
Future maturities of outstanding borrowings
Line of Credit Facility, Maximum Borrowing Capacity	25,000,000.0
Letters Of Credit Outstanding [Member]
Revolving credit facility amount	(60,000,000.0)
Future maturities of outstanding borrowings
Line of Credit Facility, Maximum Borrowing Capacity	$ 60,000,000.0
5.5% Senior Notes
Debt Instrument, Interest Rate, Effective Percentage	4.00%
Future maturities of outstanding borrowings
Financial Liabilities Fair Value Disclosure	$ 456,900,000
Minimum [Member] \| Domestic Line of Credit [Member]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	37.50%
London Interbank Offered Rate (LIBOR) [Member] \| Minimum [Member] \| Long-term Debt [Member]
Debt Instrument, Basis Spread on Variable Rate	100.00%
London Interbank Offered Rate (LIBOR) [Member] \| Minimum [Member] \| Domestic Line of Credit [Member]
Debt Instrument, Basis Spread on Variable Rate	200.00%
London Interbank Offered Rate (LIBOR) [Member] \| Maximum [Member] \| Domestic Line of Credit [Member]
Debt Instrument, Basis Spread on Variable Rate	225.00%
Base Rate [Member] \| Maximum [Member] \| Domestic Line of Credit [Member]
Debt Instrument, Basis Spread on Variable Rate	125.00%