Note 10 - Derivative Instruments and Hedging Activities - Interest Swap Contracts (Details) - Cash Flow Hedging [Member] $ in Millions	12 Months Ended
Sep. 30, 2023 USD ($)
Interest Rate Swap Agreement One [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 50.0
Derivative, fixed interest rate	1.4918%
Derivative, mark-to-market gain	$ 2.7
Interest Rate Swap Agreement Two [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 75.0
Derivative, fixed interest rate	1.6475%
Derivative, mark-to-market gain	$ 4.0
Interest Rate Swap Agreement Three [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 25.0
Derivative, fixed interest rate	1.746%
Derivative, mark-to-market gain	$ 1.5
Interest Rate Swap Agreement Four [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 50.0
Derivative, fixed interest rate	3.448%
Derivative, mark-to-market gain	$ 2.4
Interest Rate Swap Agreement Five [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 50.0
Derivative, fixed interest rate	3.685%
Derivative, mark-to-market gain	$ 0.9
Interest Rate Swap Agreement Six [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 25.0
Derivative, fixed interest rate	3.535%
Derivative, mark-to-market gain	$ 0.5
Interest Rate Swap Agreement Seven [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 25.0
Derivative, fixed interest rate	3.385%
Derivative, mark-to-market gain	$ 0.6
Interest Rate Swap Agreement Eight [Member]
Derivative, hedge term (Year)	30 years
Derivative, notional amount	$ 50.0
Derivative, fixed interest rate	2.747%
Derivative, mark-to-market gain	$ 7.8
Interest Rate Swap Agreement Nine [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 25.0
Derivative, fixed interest rate	2.902%
Derivative, mark-to-market gain	$ 2.2
Interest Rate Swap Agreement Ten [Member]
Derivative, hedge term (Year)	10 years
Derivative, notional amount	$ 25.0
Derivative, fixed interest rate	3.018%
Derivative, mark-to-market gain	$ 2.0
Interest Rate Swap [Member]
Derivative, notional amount	400.0
Derivative, mark-to-market gain	$ 24.6

Fixed interest rate related to the interest rate derivative.

No definition available.

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- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4A

+ Details

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- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-1B

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-1A

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- Definition

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Details

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