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Share-based Payment Arrangement - SENAO Share-based Compensation Plan (Detail) - Senao International Co., Ltd. (SENAO) [Member]	12 Months Ended
	Dec. 31, 2018 TWD ($)	Jul. 31, 2018 TWD ($)	Jun. 30, 2018 TWD ($)	Dec. 31, 2017 TWD ($)	Jul. 31, 2017 TWD ($)	Jun. 30, 2017 TWD ($)	Jul. 31, 2016 TWD ($)	Jun. 30, 2016 TWD ($)
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Effective Date	2012.05.28
Grant Date	2013.05.07
Stock Options Units	10,000,000
Exercise Price	$ 66.20	$ 66.20	$ 70.70	$ 70.70	$ 70.70	$ 76.10	$ 76.10	$ 81.40
Original price	$ 93.00

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The date on which share-based payment arrangements are effective.

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The date on which share-based payment arrangements are granted. [Refer: Share-based payment arrangements [member]]

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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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The exercise price of outstanding share options.

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The number of instruments granted in share-based payment arrangement.

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The weighted average share price used as input to the option pricing model to calculate the fair value of share options granted. [Refer: Option pricing model [member]; Weighted average [member]]

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