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Income Tax Expense - Reconciliation of Income Tax Expense and Accounting Profit Before Income Tax (Detail) $ in Thousands, $ in Thousands | 12 Months Ended
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Dec. 31, 2021 TWD ($) | Dec. 31, 2021 USD ($) | Dec. 31, 2020 TWD ($) | Dec. 31, 2019 TWD ($)
Reconciliation of income tax expense and accounting profit before income tax [abstract] |  |  |  |
Tax calculated based on profit before tax and statutory tax rate | $ 1,207,605 |  | $ 595,258 | $ 606,917
Effects from adjustments based on regulation | (152,618) |  | 26,974 | (162,924)
Temporary difference not recognized as deferred tax assets |  |  | (4) | (608)
Prior year income tax overestimation | (184,284) |  | (133,923) | (5,016)
Income tax on unappropriated retained earnings | 227,467 |  | 105,665 | 74,540
Effect of different tax rates in countries in which the Group operates | 148 |  | 411 | 770
Income tax expense | $ 1,098,318 | $ 39,593 | $ 594,381 | $ 513,679

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- Definition The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to foreign tax rates. [Refer: Accounting profit] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2021-01-01 -Paragraph 81 -Subparagraph c -Clause i -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=12&code=ifrs-tx-2021-en-r&anchor=para_81_c_i&doctype=Standard -URIDate 2021-03-24 + Details
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- Definition Reconciliation of income tax expense and accounting profit before income tax. + References No definition available. + Details
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- Definition Tax effect of additional income tax on unappropriated earnings. + References No definition available. + Details
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