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Pensions - Additional Information (Detail) $ in Thousands | 12 Months Ended
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Dec. 31, 2024 TWD ($) Unit | Dec. 31, 2023 TWD ($) | Dec. 31, 2022 TWD ($)
Disclosure of defined benefit plans [Line Items] |  |  |
Weighted average duration of defined benefit obligation | 9 years 3 months 18 days |  |
Defined benefit plans expected contribution | $ | $ 27,600 |  |
ChipMOS Shanghai [Member] |  |  |
Disclosure of defined benefit plans [Line Items] |  |  |
Employer contribution percentage | 16.00% | 16.00% | 16.00%
Pension costs under defined contribution pension plans | $ | $ 715 | $ 604 | $ 380
Defined benefit pension plan [Member] |  |  |
Disclosure of defined benefit plans [Line Items] |  |  |
Number of units accrued in first tranche | Unit | 2 |  |
Duration of first tranche | first 15 years |  |
Number of units accrued in second tranche | Unit | 1 |  |
Duration of second tranche | Thereafter 15 years |  |
Maximum number of units accruable under the pension plan | Unit | 45 |  |
Benefit measurement period | 6 months |  |
Employer contribution percentage | 2.00% |  |
Defined contribution pension plan [member] |  |  |
Disclosure of defined benefit plans [Line Items] |  |  |
Employer contribution percentage | 6.00% |  |
Pension costs under defined contribution pension plans | $ | $ 211,985 | $ 190,913 | $ 201,606

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- Definition The estimate of the expected contributions to be made to a defined benefit plan for the next annual reporting period. [Refer: Defined benefit plans [domain]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 147 -Subparagraph b -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_147_b&doctype=Standard -URIDate 2024-03-27 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 148 -Subparagraph d -Clause iii -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_148_d_iii&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition The amount of post-employment benefit expense relating to defined contribution plans. Defined contribution plans are post-employment benefit plans under which an entity pays fixed contributions into a separate entity (a fund) and will have no legal or constructive obligation to pay further contributions if the fund does not hold sufficient assets to pay all employee benefits relating to employee service in the current and prior periods. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 53 -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_53&doctype=Standard -URIDate 2024-03-27 + Details
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