Note 12 - Employee Benefit Plans - Assumed Health Care Cost Trend Rates (Details)	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024
Pre 65 [Member]
Health care cost trend rate assumed for next year	7.00%	7.00%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.00%	4.00%
Year that the rate reaches the ultimate trend rate	2075	2075
Post 65 [Member]
Health care cost trend rate assumed for next year	5.60%	5.60%
Rate to which the cost trend is assumed to decline (the ultimate trend rate)	4.00%	4.00%
Year that the rate reaches the ultimate trend rate	2075	2075

Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (l)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Ultimate trend rate for health care cost for defined benefit postretirement plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (k)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (l)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

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- Definition

Year ultimate health care cost trend rate is expected to be reached, in YYYY format.

+ References

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Period Type:	duration

- Details

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- Details

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