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Cash and Cash Equivalents - Additional Information (Detail) | Dec. 31, 2019 TWD ($)
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Cash and cash equivalents [abstract] |
Cash and cash equivalents pledge | $ 0

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- References No definition available. + Details
Name: | ifrs-full_CashAndCashEquivalentsAbstract
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Cash and cash equivalents pledged. + References No definition available. + Details
Name: | imos_CashAndCashEquivalentsPledged
Namespace Prefix: | imos_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant