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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

X

- 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

X

- 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

X

- 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

X

- 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

X

- Details

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