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Retirement Benefit Plans - Pension Costs Recognized in Profit and Loss for Defined Benefit Plans (Detail) - TWD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Disclosure Of Defined Plan [line items] |  |  |
Defined benefit plans pension costs recognized in profit and loss | $ 835 | $ 935 | $ 1,048
Operating costs [Member] |  |  |
Disclosure Of Defined Plan [line items] |  |  |
Defined benefit plans pension costs recognized in profit and loss | 416 | 488 | 565
Marketing expenses [Member] |  |  |
Disclosure Of Defined Plan [line items] |  |  |
Defined benefit plans pension costs recognized in profit and loss | 314 | 334 | 360
General and administrative expenses [Member] |  |  |
Disclosure Of Defined Plan [line items] |  |  |
Defined benefit plans pension costs recognized in profit and loss | 73 | 78 | 86
Research and development expenses [Member] |  |  |
Disclosure Of Defined Plan [line items] |  |  |
Defined benefit plans pension costs recognized in profit and loss | $ 32 | $ 35 | $ 37

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- Definition The amount of post-employment benefit expense included in profit or loss relating to defined benefit plans. [Refer: Profit (loss); Defined benefit plans [domain]] [Contrast: Increase (decrease) in net defined benefit liability (asset) resulting from expense (income) in profit or loss] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 5 -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_5&doctype=Standard -URIDate 2024-03-27 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2024-01-01 -Paragraph 135 -Subparagraph b -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_135_b&doctype=Standard -URIDate 2024-03-27 + Details
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