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Note 16 - Retirement Benefit Plans - Fair Value of Plan Assets (Details) - Pension Plan [Member] - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | --- | ---
Defined benefit plan assets, fair value | $ 625.1 | $ 696.4 | $ 660.5
Fair Value, Recurring [Member] |  |  |
Defined benefit plan assets, fair value | 625.1 | 696.4 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined benefit plan assets, fair value | 407.4 | 455.7 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined benefit plan assets, fair value | 0.0 | 0.0 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined benefit plan assets, fair value | 217.7 | 240.7 |
Defined Benefit Plan, Cash and Cash Equivalents [Member] |  |  |
Defined benefit plan assets, fair value | 2.9 | 19.9 |
Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Recurring [Member] |  |  |
Defined benefit plan assets, fair value | 2.9 | 19.9 |
Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined benefit plan assets, fair value | 2.9 | 19.9 |
Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined benefit plan assets, fair value | 0.0 | 0.0 |
Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined benefit plan assets, fair value | 0.0 | 0.0 |
Money Market Funds [Member] |  |  |
Defined benefit plan assets, fair value | 7.1 | 7.8 |
Money Market Funds [Member] | Fair Value, Recurring [Member] |  |  |
Defined benefit plan assets, fair value | 7.1 | 7.8 |
Money Market Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined benefit plan assets, fair value | 7.1 | 7.8 |
Money Market Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined benefit plan assets, fair value | 0.0 | 0.0 |
Money Market Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined benefit plan assets, fair value | 0.0 | 0.0 |
Bulk Annuity Policy [Member] |  |  |
Defined benefit plan assets, fair value | 217.7 | 240.7 |
Bulk Annuity Policy [Member] | Fair Value, Recurring [Member] |  |  |
Defined benefit plan assets, fair value | 217.7 | 240.7 |
Bulk Annuity Policy [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined benefit plan assets, fair value | 0.0 | 0.0 |
Bulk Annuity Policy [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined benefit plan assets, fair value | 0.0 | 0.0 |
Bulk Annuity Policy [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined benefit plan assets, fair value | 217.7 | 240.7 |
Fixed Income Investments [Member] |  |  |
Defined benefit plan assets, fair value | 269.0 | 300.6 |
Fixed Income Investments [Member] | Fair Value, Recurring [Member] |  |  |
Defined benefit plan assets, fair value | 269.0 | 300.6 |
Fixed Income Investments [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined benefit plan assets, fair value | 269.0 | 300.6 |
Fixed Income Investments [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined benefit plan assets, fair value | 0.0 | 0.0 |
Fixed Income Investments [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined benefit plan assets, fair value | 0.0 | 0.0 |
Equity Funds [Member] |  |  |
Defined benefit plan assets, fair value | 128.4 | 127.4 |
Equity Funds [Member] | Fair Value, Recurring [Member] |  |  |
Defined benefit plan assets, fair value | 128.4 | 127.4 |
Equity Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined benefit plan assets, fair value | 128.4 | 127.4 |
Equity Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined benefit plan assets, fair value | 0.0 | 0.0 |
Equity Funds [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined benefit plan assets, fair value | $ 0.0 | $ 0.0 |

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- 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 Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
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