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Note 12 - Employee Benefit Plans - Allocation of Plans' Assets (Details) - USD ($)	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Pension Plan [Member]
Asset	$ 30,487,401	$ 31,054,138	$ 26,878,661
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	11,027,023	11,548,901
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	19,460,378	19,505,237
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Other Postretirement Benefits Plan [Member]
Asset	15,390,822	15,078,281	$ 13,019,313
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	15,390,822	15,078,281
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	$ 0	$ 0
Defined Benefit Plan, Equity Securities [Member] | Pension Plan [Member]
Target	25.00%
Asset	23.00%	25.00%
Defined Benefit Plan, Equity Securities [Member] | Other Postretirement Benefits Plan [Member]
Target	30.00%
Asset	38.00%	48.00%
Defined Benefit Plan, Debt Security [Member] | Pension Plan [Member]
Target	75.00%
Asset	77.00%	75.00%
Defined Benefit Plan, Debt Security [Member] | Other Postretirement Benefits Plan [Member]
Target	70.00%
Asset	53.00%	36.00%
Defined Benefit Plan, Cash [Member] | Pension Plan [Member]
Asset	$ 27,603	$ 142,921
Defined Benefit Plan, Cash [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	27,603	142,921
Defined Benefit Plan, Cash [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Cash [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	$ 0	$ 0
Defined Benefit Plan, Cash [Member] | Other Postretirement Benefits Plan [Member]
Asset	9.00%	16.00%
Asset	$ 1,462,600	$ 2,381,909
Defined Benefit Plan, Cash [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	1,462,600	2,381,909
Defined Benefit Plan, Cash [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Cash [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Common Collective Trust And Pooled Fund Bonds, Liability Driven Investment [Member] | Pension Plan [Member]
Asset	19,460,378	19,505,237
Defined Benefit Plan, Common Collective Trust And Pooled Fund Bonds, Liability Driven Investment [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	0	0
Defined Benefit Plan, Common Collective Trust And Pooled Fund Bonds, Liability Driven Investment [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	19,460,378	19,505,237
Defined Benefit Plan, Common Collective Trust And Pooled Fund Bonds, Liability Driven Investment [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Mutual Fund Bonds, Domestic Fixed Income [Member] | Other Postretirement Benefits Plan [Member]
Asset	8,089,514	5,457,976
Defined Benefit Plan, Mutual Fund Bonds, Domestic Fixed Income [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	8,089,514	5,457,976
Defined Benefit Plan, Mutual Fund Bonds, Domestic Fixed Income [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Mutual Fund Bonds, Domestic Fixed Income [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Mutual Fund [Member] | Pension Plan [Member]
Asset	3,901,202	3,791,697
Mutual Fund [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	3,901,202	3,791,697
Mutual Fund [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Mutual Fund [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Large Cap Growth [Member] | Pension Plan [Member]
Asset	2,161,688	2,073,092
Defined Benefit Plan, Equity Funds, Domestic Large Cap Growth [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	2,161,688	2,073,092
Defined Benefit Plan, Equity Funds, Domestic Large Cap Growth [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Large Cap Growth [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Large Cap Growth [Member] | Other Postretirement Benefits Plan [Member]
Asset	1,340,584	2,412,824
Defined Benefit Plan, Equity Funds, Domestic Large Cap Growth [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	1,340,584	2,412,824
Defined Benefit Plan, Equity Funds, Domestic Large Cap Growth [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Large Cap Growth [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Large Cap Value [Member] | Pension Plan [Member]
Asset	2,470,055	2,469,045
Defined Benefit Plan, Equity Funds, Domestic Large Cap Value [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	2,470,055	2,469,045
Defined Benefit Plan, Equity Funds, Domestic Large Cap Value [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Large Cap Value [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Large Cap Value [Member] | Other Postretirement Benefits Plan [Member]
Asset	2,799,537	1,996,262
Defined Benefit Plan, Equity Funds, Domestic Large Cap Value [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	2,799,537	1,996,262
Defined Benefit Plan, Equity Funds, Domestic Large Cap Value [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Large Cap Value [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Small/Mid Cap Core [Member] | Pension Plan [Member]
Asset	1,023,627	1,297,579
Defined Benefit Plan, Equity Funds, Domestic Small/Mid Cap Core [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	1,023,627	1,297,579
Defined Benefit Plan, Equity Funds, Domestic Small/Mid Cap Core [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Small/Mid Cap Core [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Small/Mid Cap Core [Member] | Other Postretirement Benefits Plan [Member]
Asset	453,828	738,393
Defined Benefit Plan, Equity Funds, Domestic Small/Mid Cap Core [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	453,828	738,393
Defined Benefit Plan, Equity Funds, Domestic Small/Mid Cap Core [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Domestic Small/Mid Cap Core [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Mutual Funds, Foreign Large Cap Growth [Member] | Other Postretirement Benefits Plan [Member]
Asset	217,707	532,391
Defined Benefit Plan, Mutual Funds, Foreign Large Cap Growth [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	217,707	532,391
Defined Benefit Plan, Mutual Funds, Foreign Large Cap Growth [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Mutual Funds, Foreign Large Cap Growth [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Equity Mutual Funds, Foreign Large Cap Growth [Member] | Pension Plan [Member]
Asset	442,847	498,732
Defined Benefit Plan, Equity Mutual Funds, Foreign Large Cap Growth [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	442,847	498,732
Defined Benefit Plan, Equity Mutual Funds, Foreign Large Cap Growth [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Equity Mutual Funds, Foreign Large Cap Growth [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Foreign Large Cap Core [Member] | Pension Plan [Member]
Asset	530,180	793,613
Defined Benefit Plan, Equity Funds, Foreign Large Cap Core [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	530,180	793,613
Defined Benefit Plan, Equity Funds, Foreign Large Cap Core [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Foreign Large Cap Core [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Foreign Large Cap Core [Member] | Other Postretirement Benefits Plan [Member]
Asset	1,027,052	906,503
Defined Benefit Plan, Equity Funds, Foreign Large Cap Core [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	1,027,052	906,503
Defined Benefit Plan, Equity Funds, Foreign Large Cap Core [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Foreign Large Cap Core [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Foreign Large Cap Value [Member] | Pension Plan [Member]
Asset	469,821	482,222
Defined Benefit Plan, Equity Funds, Foreign Large Cap Value [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset	469,821	482,222
Defined Benefit Plan, Equity Funds, Foreign Large Cap Value [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset	0	0
Defined Benefit Plan, Equity Funds, Foreign Large Cap Value [Member] | Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset	$ 0	0
Defined Benefit Plan, Equity Funds, Foreign Large Cap Value [Member] | Other Postretirement Benefits Plan [Member]
Asset		652,023
Defined Benefit Plan, Equity Funds, Foreign Large Cap Value [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member]
Asset		652,023
Defined Benefit Plan, Equity Funds, Foreign Large Cap Value [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member]
Asset		0
Defined Benefit Plan, Equity Funds, Foreign Large Cap Value [Member] | Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member]
Asset		$ 0

X

- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

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