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Related Party Transactions - Summary of Names of Related Parties and Relationship (Detail) | 12 Months Ended
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Dec. 31, 2020
Unimos Shanghai [member] |
Disclosure of transactions between related parties [Line Items] |
Relationship | Associate
JMC ELECTRONICS CO., LTD. [member] |
Disclosure of transactions between related parties [Line Items] |
Relationship | Associate

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- Definition The description of the nature of the related party relationships. [Refer: Related parties [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 24 -IssueDate 2020-01-01 -Paragraph 18 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=24&code=ifrs-tx-2020-en-r&anchor=para_18&doctype=Standard -URIDate 2020-01-01 + Details
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Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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Namespace Prefix: | ifrs-full_
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Balance Type: | na
Period Type: | duration

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- Details
Name: | ifrs-full_SignificantInvestmentsInAssociatesAxis=imos_UnimosShanghaiMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_SignificantInvestmentsInAssociatesAxis=imos_JMCELECTRONICSCOLTDMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |