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Note 12 - Employee Benefit Plans - Schedule of Employer Contributions (Details) - The 401K Plan [Member] - USD ($) | 12 Months Ended
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Sep. 30, 2025 | Sep. 30, 2024
Matching contribution | $ 466,630 | $ 427,022
Employer contributions | $ 137,114 | $ 112,207

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 70 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480794/715-70-50-1 + Details
Name: | us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Amount of discretionary contributions made by an employer to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | us-gaap_RetirementPlanNameAxis=rgco_The401KPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |