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Investment in Associates - Details of Investment in Associates (Detail) $ in Thousands, $ in Thousands		12 Months Ended
	Apr. 08, 2019	Dec. 31, 2019 TWD ($)	Dec. 31, 2018 TWD ($)	Dec. 31, 2019 USD ($)
Disclosure of associates [line items]
Carrying amount		$ 3,392,910	$ 3,863,741	$ 113,437
JMC ELECTRONICS CO., LTD. [member]
Disclosure of associates [line items]
Principal place of business		Kaohsiung, Taiwan
Measurement method		Equity method
Carrying amount		$ 249,793	$ 406,792
Shareholding ratio	10.00%	10.00%	19.10%
Nature of relationship		Strategic Investee
Unimos Shanghai [member]
Disclosure of associates [line items]
Principal place of business		Shanghai, PRC
Measurement method		Equity method
Carrying amount		$ 3,143,117	$ 3,456,949
Shareholding ratio		45.02%	45.02%
Nature of relationship		Strategic Investee

X

- Definition

The country in which an associate of the entity is incorporated. [Refer: Associates [member]]

+ References

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X

- Definition

The description of the nature of the entity's relationship with an associate (for example, describing the nature of the activities of the associate and whether they are strategic to the entity's activities). [Refer: Associates [member]]

+ References

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- Definition

The description of whether the investment in an associate is measured using the equity method or at fair value. [Refer: At fair value [member]; Associates [member]]

+ References

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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.

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No definition available.

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- Definition

The amount of investments in associates accounted for using the equity method. [Refer: Associates [member]; Investments accounted for using equity method]

+ References

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- Definition

The proportion of ownership interest in an associate attributable to the entity. [Refer: Associates [member]]

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