Note 10 - Other Income (Details Textual) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Investment Income, Interest	$ 2.0	$ 2.1	$ 4.0	$ 3.9

Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 220
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-Publisher FASB
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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