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Retirement Benefit Plans - Additional Information (Detail) $ in Thousands, $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 TWD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 TWD ($) | Dec. 31, 2017 TWD ($) | Dec. 31, 2019 USD ($)
Disclosure of defined benefit plans [line items] |  |  |  |  |
Percentage of monthly pension contributions | 6.00% | 6.00% | 6.00% | 6.00% |
Pension costs | $ 277,041 | $ 9,263 | $ 291,333 | $ 266,267 |
Expected contribution to defined benefit plans | 533,777 | 17,846 | 484,247 |  |
Pension plans for executive managers [member] |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |
Pension costs | 11,567 | $ 387 | 11,137 | $ 3,171 |
Accrued pension liabilities | $ 335,109 |  | $ 320,542 |  | $ 11,204
Bottom of range [member] |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |
Average duration of the defined benefit obligation | 10 years | 10 years | 9 years |  |
Top of range [member] |  |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |  |
Average duration of the defined benefit obligation | 14 years | 14 years | 15 years |  |

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- Definition Percentage of employees monthly wages and salaries as contributions to defined benefit plan + References No definition available. + Details
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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 estimate of the expected contributions to be made to a defined benefit plan for the next annual reporting period. [Refer: Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2019-01-01 -Paragraph 147 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_147_b&doctype=Standard -URIDate 2019-03-27 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2019-01-01 -Paragraph 148 -Subparagraph d -Clause iii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_148_d_iii&doctype=Standard -URIDate 2019-03-27 + Details
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- Definition The amount of post-employment benefit expense relating to defined benefit plans. [Refer: Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2019-01-01 -Paragraph 5 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_5&doctype=Standard -URIDate 2019-03-27 + Details
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- Definition The amount of deficit in a defined benefit plan. [Refer: Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2019-01-01 -Paragraph 55 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_55&doctype=Standard -URIDate 2019-03-27 + Details
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- Definition The weighted average duration of a defined benefit obligation. [Refer: Weighted average [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2019-01-01 -Paragraph 147 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2019-en-r&anchor=para_147_c&doctype=Standard -URIDate 2019-03-27 + Details
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