Note 13 - Regulatory Assets and Liabilities - Schedule of Regulatory Liabilities (Details) - USD ($)	Jun. 30, 2026	Sep. 30, 2025
Regulatory liabilities	$ 2,103,199	$ 1,638,911
Regulatory cost of retirement obligations	17,016,675	15,869,691
Regulatory Liability, Noncurrent	14,359,465	17,371,430
Total non-current	31,376,140	33,241,121
Total regulatory liabilities	33,479,339	34,880,032
Rate Refund [Member]
Regulatory liabilities	275,400	0
Deferred Income Tax Charge [Member]
Regulatory liabilities	591,764	591,764
Regulatory Liability, Noncurrent	10,637,754	13,649,719
Supplier Refund [Member]
Regulatory liabilities	1,196,640	889,564
Other Deferred Liabilities [Member]
Regulatory liabilities	39,395	157,583
Other Regulatory Assets (Liabilities) [Member]
Regulatory Liability, Noncurrent	$ 3,721,711	$ 3,721,711

Regulatory cost of retirement obligations not otherwise included in ARO.

No definition available.

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Namespace Prefix:	rgco_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of regulatory liabilities and asset retirement obligations classified as noncurrent.

+ References

No definition available.

+ Details

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Namespace Prefix:	rgco_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-SubTopic 405
-Name Accounting Standards Codification
-Section 25
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477571/980-405-25-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount for the individual regulatory current liability as itemized in a table of regulatory current liabilities as of the end of the period.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(24))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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- Details

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- Details

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- Details

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