Note 11 - Concentrations of Credit Risk (Details Textual) Pure in Millions, $ in Millions	12 Months Ended
Sep. 30, 2023 USD ($)
Customer Concentration Risk [Member] \| Utility Companies and Their Marketing Affiliates [Member]
Accounts Receivable, after Allowance for Credit Loss	$ 53.4
Customer Concentration Risk [Member] \| Five Largest Counterparties [Member]
Accounts Receivable, after Allowance for Credit Loss	$ 26.7
Gas Utility [Member]
Number of Customer Serves	1.7

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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