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Pensions - Additional Information (Detail) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2021 TWD ($) Unit | Dec. 31, 2020 TWD ($) | Dec. 31, 2019 TWD ($)
Disclosure of defined benefit plans [Line Items] |  |  |
Weighted average duration of defined benefit obligation | 12 years 2 months 12 days |  |
ChipMOS Shanghai [Member] |  |  |
Disclosure of defined benefit plans [Line Items] |  |  |
Employer contribution percentage | 16.00% | 16.00% |
Pension costs under defined contribution pension plans | $ | $ 209 | $ 0 |
Defined benefit pension plan [Member] |  |  |
Disclosure of defined benefit plans [Line Items] |  |  |
Number of units accrued in first tranche | 2 |  |
Duration of first tranche | first 15 years |  |
Number of units accrued in second tranche | 1 |  |
Duration of second tranche | Thereafter 15 years |  |
Maximum number of units accruable under the pension plan | 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 | $ | $ 197,076 | $ 184,562 | $ 187,502

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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table. + References No definition available. + 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 2021-01-01 -Paragraph 53 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2021-en-r&anchor=para_53&doctype=Standard -URIDate 2021-03-24 + Details
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- Definition The weighted average duration of a defined benefit obligation. [Refer: Weighted average [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2021-01-01 -Paragraph 147 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2021-en-r&anchor=para_147_c&doctype=Standard -URIDate 2021-03-24 + Details
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- Definition Defined contribution plans employer contribution percentage. + References No definition available. + Details
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