Credit Facilities, Short-term Borrowings and Long-term Debt (Schedule of Long-term Debt) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Debt Instrument [Line Items]
Long-term debt	$ 721,526	$ 710,616
Unamortized debt issuance costs	(1,145)	(1,438)
Less: Current portion of long-term debt	75,817	856
Long-term debt, less current portion	645,709	709,760
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	85,000
Series H Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 25,000	25,000
Interest rate	4.03%
Maturity date	Nov. 15, 2023
Series I Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 25,000	25,000
Interest rate	4.18%
Maturity date	Nov. 15, 2025
Series K Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 50,000	50,000
Interest rate	4.03%
Maturity date	Nov. 15, 2023
Series L Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 50,000	50,000
Interest rate	4.18%
Maturity date	Nov. 15, 2025
Series M Notes [Member]
Debt Instrument [Line Items]
Maturity date	Sep. 23, 2026
Series M Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 42,280	39,198
Interest rate	1.12%
Maturity date	Sep. 23, 2026
Series N Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 81,390	75,457
Interest rate	1.31%
Maturity date	Sep. 23, 2028
Series O Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 45,451	42,138
Interest rate	1.57%
Maturity date	Sep. 23, 2031
Series P Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 85,000	85,000
Interest rate	4.27%
Maturity date	May 30, 2025
Series Q Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt		85,000
Interest rate	4.35%
Maturity date	May 30, 2027
Series R Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 75,000	75,000
Interest rate	4.41%
Maturity date	May 30, 2029
Series S Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 75,000	75,000
Interest rate	4.46%
Maturity date	May 30, 2030
Finance Leases [Member]
Debt Instrument [Line Items]
Long-term debt		5,261
Finance Leases [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 3,550
Series T Notes [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term debt	$ 80,000	$ 80,000
Interest rate	4.61%
Maturity date	May 30, 2033