XML 182 R102.htm IDEA: XBRL DOCUMENT
v3.20.1

Income Tax Expense - Additional Information (Detail) - TWD ($) $ in Thousands |  |  | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Jan. 01, 2018 | Oct. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2019 | Dec. 31, 2018
Disclosure of income tax expense [Line Items] |  |  |  |  |
Taxable temporary differences not recognized as deferred tax liaibility |  |  |  | $ 180,395 | $ 495,154
Reduction of unappropriated retained earnings through capital transfer |  | $ (5,052,343) |  |  |
Profit seeking enterprise [member] |  |  |  |  |
Disclosure of income tax expense [Line Items] |  |  |  |  |
Statutory tax rates | 20.00% |  | 17.00% |  |
unappropriated retained earnings tax rate | 5.00% |  | 10.00% |  |

X
- Definition The applicable income tax rate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2019-01-01 -Paragraph 81 -Subparagraph c -Clause ii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2019-en-r&anchor=para_81_c_ii&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_ApplicableTaxRate
Namespace Prefix: | ifrs-full_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Decrease unappropriated retained earnings through transfer to capital. + References No definition available. + Details
Name: | imos_DecreaseUnappropriatedRetainedEarningsThroughTransferToCapital
Namespace Prefix: | imos_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Deductible temporary differences for which no deferred tax liability is recognized. + References No definition available. + Details
Name: | imos_DeductibleTemporaryDifferencesForWhichNoDeferredTaxLiabilityIsRecognised
Namespace Prefix: | imos_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Disclosure of income tax expense. + References No definition available. + Details
Name: | imos_DisclosureOfIncomeTaxExpenseLineItems
Namespace Prefix: | imos_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Unappropriated retained earnings tax rate. + References No definition available. + Details
Name: | imos_UnappropriatedRetainedEarningsTaxRate
Namespace Prefix: | imos_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=imos_ProfitSeekingEnterpriseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |