Note 11 - Concentrations of Credit Risk (Details Textual) Pure in Millions, $ in Millions	12 Months Ended
Sep. 30, 2022 USD ($)
Customer Concentration Risk [Member] \| Utility Companies and Their Marketing Affiliates [Member]
Accounts Receivable, after Allowance for Credit Loss, Total	$ 245.6
Customer Concentration Risk [Member] \| Five Largest Counterparties [Member]
Accounts Receivable, after Allowance for Credit Loss, Total	$ 111.2
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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 954
-SubTopic 310
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=126942793&loc=d3e3073-115593

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(5))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Name:	us-gaap_AccountsReceivableNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant