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Related Party Transactions - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 TWD ($)
Disclosure of transactions between related parties [Line Items]
Acquisition of investment in associate	$ 794,694
ChipMOS BVI and Unimos Shanghai [member]
Disclosure of transactions between related parties [Line Items]
Acquisition of investment in associate	$ 794,694

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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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- Definition

The cash outflow for the purchase of interests in associates. [Refer: Associates [member]]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2020-01-01
-Paragraph 16
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=7&code=ifrs-tx-2020-en-r&anchor=para_16&doctype=Standard
-URIDate 2020-01-01

+ Details

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Balance Type:	credit
Period Type:	duration

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- Details

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Period Type: