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v3.25.1

Significant events after the reporting period - Additional Information (Detail) - Major ordinary share transactions [member] - TWD ($) shares in Thousands, $ in Thousands |  | 2 Months Ended | 3 Months Ended
--- | --- | --- | ---
Apr. 15, 2025 | Mar. 21, 2025 | Mar. 31, 2025
Significant Events After The Reporting Period [Line Items] |  |  |
Repurchase of shares |  | 10,000 |
Transaction amount for repurchasing shares |  |  | $ 321,705
Cancel of treasury stock shares | 10,000 |  |

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- Definition Cancel of treasury stock shares. + References No definition available. + Details
Name: | imos_CancelOfTreasuryStockShares
Namespace Prefix: | imos_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

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- Definition Repurchase of shares. + References No definition available. + Details
Name: | imos_RepurchaseOfShares
Namespace Prefix: | imos_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

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- Definition Significant events after the reporting period. + References No definition available. + Details
Name: | imos_SignificantEventsAfterTheReportingPeriodLineItems
Namespace Prefix: | imos_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Transaction amount for repurchasing shares. + References No definition available. + Details
Name: | imos_TransactionAmountForRepurchasingShares
Namespace Prefix: | imos_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | ifrs-full_NonadjustingEventsAfterReportingPeriodAxis=ifrs-full_MajorOrdinaryShareTransactionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |