XML 191 R168.htm IDEA: XBRL DOCUMENT
v3.21.1

Financial Risk Management and Fair Values of Financial Instruments - Summary of Qualitative Information and Sensitivity Analysis of Changes in Significant Unobservable Inputs Under Valuation Model Used in Level Fair Value Measurement (Detail) - TWD ($) | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Non derivative equity instruments [member] | Foreign unlisted stocks [member] |  |
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items] |  |
Fair value | $ 262,007,000 | $ 121,808,000
Valuation technique | Comparable companies | Comparable companies
Non derivative equity instruments [member] | Foreign unlisted stocks [member] | Price book value multiple [member] |  |
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items] |  |
Range (weighted average method) | $ 1.97 | $ 1.22
Relationship of inputs to fair value | The higher the multiple, the higher the fair value | The higher the multiple, the higher the fair value
Non derivative equity instruments [member] | Foreign unlisted stocks [member] | Enter prise value EBITDA multiple [member] |  |
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items] |  |
Range (weighted average method) | $ 12.00 | $ 10.51
Relationship of inputs to fair value | The higher the multiple, the higher the fair value | The higher the multiple, the higher the fair value
Non derivative equity instruments [member] | Foreign unlisted stocks [member] | Discount for lack of marketability [member] |  |
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items] |  |
Range (weighted average method) | 15.80% | 15.80%
Relationship of inputs to fair value | The higher the discount for lack of marketability, the lower the fair value | The higher the discount for lack of marketability, the lower the fair value
Non derivative debt instruments [member] | Foreign partnership interest [member] |  |
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items] |  |
Fair value | $ 10,368,000 | $ 11,038,000
Valuation technique | Discounted cash flow | Discounted cash flow
Non derivative debt instruments [member] | Foreign partnership interest [member] | Discount rate [member] |  |
Disclosure of significant unobservable inputs used in fair value measurement of equity [line items] |  |
Range (weighted average method) | 0.30% | 0.30%
Relationship of inputs to fair value | The lower the discount rate, the higher the fair value | The lower the discount rate, the higher the fair value

X
- 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
Name: | ifrs-full_DisclosureOfSignificantUnobservableInputsUsedInFairValueMeasurementOfEquityLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value financial instruments. + References No definition available. + Details
Name: | imos_FairValueFinancialInstruments
Namespace Prefix: | imos_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Relationship of inputs to fair value. + References No definition available. + Details
Name: | imos_RelationshipOfInputsToFairValue
Namespace Prefix: | imos_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Valuation technique. + References No definition available. + Details
Name: | imos_ValuationTechnique
Namespace Prefix: | imos_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted Average Interest Rate of Financial Instrument + References No definition available. + Details
Name: | imos_WeightedAverageInterestRateOfFinancialInstrument
Namespace Prefix: | imos_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted Average Interest Rate of Financial Instruments. + References No definition available. + Details
Name: | imos_WeightedAverageInterestRateOfFinancialInstruments
Namespace Prefix: | imos_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | ifrs-full_ClassesOfFinancialAssetsAxis=imos_NonderivativeEquityInstrumentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ClassesOfFinancialInstrumentsAxis=imos_ForeignUnlistedStocksMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ValuationTechniquesUsedInFairValueMeasurementAxis=imos_PriceBookValueMultipleMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ValuationTechniquesUsedInFairValueMeasurementAxis=imos_EnterPriseValueEBITDAMultipleMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ValuationTechniquesUsedInFairValueMeasurementAxis=imos_DiscountForLackOfMarketabilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ClassesOfFinancialAssetsAxis=imos_NonderivativeDebtInstrumentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ClassesOfFinancialInstrumentsAxis=imos_ForeignPartnershipInterestMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ValuationTechniquesUsedInFairValueMeasurementAxis=imos_DiscountRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |