Note 7 - Long-Term Debt - Long-term Debt (Details) (Parentheticals)	6 Months Ended	9 Months Ended
Jun. 30, 2026	Sep. 30, 2025
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%
Roanoke Gas Company [Member] \| Unsecured Delayed-draw Term Note Payable [Member] \| Unsecured Delayed-draw Term Note Payable at Term SOFR Plus 1.00%, Due August 20, 2029 [Member]
Basis spread	1.00%
Derivative fixed interest rate	5.13%
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] \| Unsecured Senior Notes Payable [Member] \| Unsecured Term Note Payable at Term SOFR Plus 1.55%, Due September 5, 2032 [Member]
Basis spread	1.55%	1.55%
RGC Midstream LLC [Member] \| Unsecured Senior Notes Payable [Member] \| Unsecured Term Note Payable at Term SOFR Plus 1.55%, 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 at Term SOFR Plus 1.55%, 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 at Term SOFR Plus 1.55%, Due September 5, 2032 2 [Member]
Basis spread	1.55%	1.55%
Derivative fixed interest rate	5.061%	5.061%

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]

Roanoke Gas Company [Member] | Unsecured Senior Notes Payable [Member] | Unsecured term note payable, at Term SOFR plus 1.00%, due October 1, 2028 [Member]

Roanoke Gas Company [Member] | Unsecured Delayed-draw Term Note Payable [Member] | Unsecured Delayed-draw Term Note Payable at Term SOFR Plus 1.00%, Due August 20, 2029 [Member]

RGC Midstream LLC [Member] | Southgate Revolving Credit Facility [Member] | Revolving Credit Facility [Member]

RGC Midstream LLC [Member] | Boost Revolving Credit Facility [Member] | Revolving Credit Facility [Member]

RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable at Term SOFR Plus 1.55%, Due September 5, 2032 [Member]

RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable at Term SOFR Plus 1.55%, Due September 5, 2032 [Member] | Four M Swap [Member]

RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable at Term SOFR Plus 1.55%, Due September 5, 2032 [Member] | Twenty Point Six M Swap [Member]

RGC Midstream LLC [Member] | Unsecured Senior Notes Payable [Member] | Unsecured Term Note Payable at Term SOFR Plus 1.55%, Due September 5, 2032 2 [Member]