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Note 4 - Regulatory Matters (Details Textual)						12 Months Ended
	Dec. 02, 2025 USD ($)	Sep. 26, 2025 USD ($)	May 30, 2025 USD ($)	Oct. 16, 2024 USD ($)	Feb. 02, 2024 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2022	Jun. 02, 2022
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 4,330,000
Public Utilities, Approved Return on Equity, Percentage				9.90%	9.44%
Public Utilities, Requested Return on Equity, Percentage					10.35%
Public Utilities, Approved Rate Increase (Decrease), Amount				$ 4,080,000.00
RNG Rider Revenue Requirement			$ 1,660,000
RNG Rider Impact to Customers			699,000
SAVE Annual Revenues		$ 2,610,000	2,640,000
Recovery Costs, SAVE Eligible Expenses			$ 10,330,000
Number of Locations, Natural Gas Delivery Assets, Requested Acquisition									5
Number of Locations, Natural Gas Delivery Assets, Approved Acquisition						1	1	2
Natural Gas Delivery Assets [Member] | Housing Authority Management [Member]
Asset Acquisition, Recognized Pre-tax Gain						$ 762,000	$ 782,000
Subsequent Event [Member]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 4,300,000

X

- Definition

Amount of recognized pre-tax gain from the acquisition of assets.

+ References

No definition available.

+ Details

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Namespace Prefix:	rgco_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Number of locations where the request for asset acquisition of natural gas delivery has been approved.

+ References

No definition available.

+ Details

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Namespace Prefix:	rgco_
Data Type:	xbrli:integerItemType
Balance Type:	na
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X

- Definition

Number of locations where the acquisition of assets related to natural gas delivery has been requested.

+ References

No definition available.

+ Details

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Namespace Prefix:	rgco_
Data Type:	xbrli:integerItemType
Balance Type:	na
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X

- Definition

Represents the recovery costs associated with SAVE eligible expenses.

+ References

No definition available.

+ Details

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Namespace Prefix:	rgco_
Data Type:	xbrli:monetaryItemType
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X

- Definition

The impact to customers after adjustments.

+ References

No definition available.

+ Details

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

X

- Definition

The gross revenue for the RNG rider program.

+ References

No definition available.

+ Details

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

X

- Definition

The represented annual revenues under the SAVE program.

+ References

No definition available.

+ Details

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

X

- Definition

Amount of public utility's approved rate increase (decrease) by regulatory agency.

+ References

No definition available.

+ Details

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

- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

+ Details

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X

- Definition

Amount of public utility's requested rate increase (decrease) with regulatory agency.

+ References

No definition available.

+ Details

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X

- Definition

Percentage of public utility's requested return on equity.

+ References

No definition available.

+ Details

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- Details

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