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Retirement Benefit Plans - Assets Measured at Fair Value on Recurring Basis for Pension Plan (Detail) - Pension Plans - USD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | $ 148,974 | $ 137,893 | $ 126,098
Mutual Fund |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | 140,148 | 127,881 |
Mutual Fund | Equity Funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | 78,407 | 78,522 |
Mutual Fund | Fixed Income Securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | 61,741 | 49,359 |
Cash and Cash Equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | 1,504 | 2,266 |
Mutual Fund Including Cash And Cash Equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | 141,652 | 130,147 |
Real Estate Funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | 7,322 | 7,746 |
Fair Value, Inputs, Level 1 | Mutual Fund |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | 140,148 | 127,881 |
Fair Value, Inputs, Level 1 | Mutual Fund | Equity Funds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | 78,407 | 78,522 |
Fair Value, Inputs, Level 1 | Mutual Fund | Fixed Income Securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | 61,741 | 49,359 |
Fair Value, Inputs, Level 1 | Cash and Cash Equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | 1,504 | 2,266 |
Fair Value, Inputs, Level 1 | Mutual Fund Including Cash And Cash Equivalents |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Plan assets measured at fair value | $ 141,652 | $ 130,147 |

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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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