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Note 7 - Long-term Debt - Long-term Debt (Details) (Parentheticals) | 12 Months Ended
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Sep. 30, 2025 | Sep. 30, 2024
Roanoke Gas Company [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Senior Notes Payable, at 4.26%, Due on September 18, 2034 [Member] |  |
Stated rate | 4.26% | 4.26%
Roanoke Gas Company [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Notes Payable, at 3.58%, Due on October 2, 2027 [Member] |  |
Stated rate | 3.58% | 3.58%
Roanoke Gas Company [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Notes Payable, at 4.41 %, Due on March 28, 2031 [Member] |  |
Stated rate | 4.41% | 4.41%
Roanoke Gas Company [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Notes Payable, at 3.60%, Due on December 6, 2029 [Member] |  |
Stated rate | 3.60% | 3.60%
Roanoke Gas Company [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Notes Payable, at 30-day SOFR Average 1.20% Due August 20, 2026 [Member] |  |
Basis spread | 1.20% | 1.20%
Derivative fixed interest rate | 2.00% | 2.00%
Roanoke Gas Company [Member] | Unsecured Senior Notes Payable [Member] | Unsecured term note payable, at Term SOFR plus 1.00%, due October 1, 2028 [Member] |  |
Basis spread | 1.00% | 1.00%
Derivative fixed interest rate | 2.49% | 2.49%
RGC Midstream LLC [Member] | Southgate Revolving Credit Facility [Member] | Revolving Credit Facility [Member] |  |
Basis spread | 1.75% | 1.75%
RGC Midstream LLC [Member] | Boost Revolving Credit Facility [Member] | Revolving Credit Facility [Member] |  |
Basis spread | 1.75% | 1.75%
RGC Midstream LLC [Member] | Revolving Credit Facility Retired September 5, 2025 [Member] | Revolving Credit Facility [Member] |  |
Basis spread | 2.215% | 2.215%
RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable Due September 5, 2032 [Member] |  |
Basis spread | 1.55% | 1.55%
RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable Due September 5, 2032 [Member] | Fourteen M Swap [Member] |  |
Derivative fixed interest rate | 3.24% | 3.24%
RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable Due September 5, 2032 [Member] | Four M Swap [Member] |  |
Derivative fixed interest rate | 2.443% | 2.443%
RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable Due September 5, 2032 [Member] | Twenty Point Six M Swap [Member] |  |
Derivative fixed interest rate | 5.061% | 5.061%
RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable Due September 5, 2032 2 [Member] |  |
Basis spread | 1.55% | 1.55%
Derivative fixed interest rate | 5.061% | 5.061%
RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable Retired September 5, 2025 [Member] |  |
Stated rate | 1.55% | 1.55%
RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable Retired September 5, 2025 2 [Member] |  |
Basis spread | 1.26448% | 1.26448%
Derivative fixed interest rate | 3.24% | 3.24%
RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable Retired September 5, 2025 3 [Member] |  |
Basis spread | 1.26448% | 1.26448%
Derivative fixed interest rate | 2.443% | 2.443%

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)(a)(1)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 470 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B + Details
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