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

X

- 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

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- 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

X

- Details

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