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Note 4 - Income Taxes - Income Positions (Details) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Mar. 31, 2022 | Mar. 31, 2021 | Mar. 31, 2022 | Mar. 31, 2021
Effective tax rate | 26.10% | 25.20% | 26.60% | 24.80%
Effective tax rate excluding LLC impairment | 24.00% |  | 23.70% |
Effective Income Tax Rate, Including the Effect of Impaired Investment [Member] |  |  |  |
Effective tax rate - LLC impairment | 25.70% | 0.00% | 25.70% | 0.00%
Effective Income Tax Rate, Excluding the Effect of Impaired Investment [Member] |  |  |  |
Effective tax rate excluding LLC impairment | 24.00% | 25.20% | 23.70% | 24.80%

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- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) including the impaired investment. + References No definition available. + Details
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- Definition Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI https://asc.fasb.org/extlink&oid=121826272&loc=d3e32687-109319 + Details
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