Contents of Significant Accounts - Post-Employment Benefits - Additional Information (Detail) - TWD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disclosure of defined benefit plans and defined contribution plans [Line Items]
Actual returns on plan assets	$ 241	$ 37
Expected pension fund contribution in 2025	$ 490
Weighted-average durations of defined benefit obligation	8 years	6 years
Defined benefit plan [member]
Disclosure of defined benefit plans and defined contribution plans [Line Items]
Percentages of employees' total monthly salaries and wages to pension fund	2.00%	2.00%	2.00%
Pension expenses	$ 35	$ 45	$ 34
Defined contribution plan [member]
Disclosure of defined benefit plans and defined contribution plans [Line Items]
Percentage of employees' monthly salary or wages as monthly contributions to defined contribution plan	6.00%	6.00%	6.00%
Pension expenses	$ 1,978	$ 1,655	$ 1,880

The estimate of the expected contributions to be made to a defined benefit plan for the next annual reporting period. [Refer: Defined benefit plans [domain]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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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
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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The amount of post-employment benefit expense relating to defined contribution plans. Defined contribution plans are post-employment benefit plans under which an entity pays fixed contributions into a separate entity (a fund) and will have no legal or constructive obligation to pay further contributions if the fund does not hold sufficient assets to pay all employee benefits relating to employee service in the current and prior periods.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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
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Actual return on plan assets.

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Disclosure of defined benefit plans and defined contribution plans [Line Items]

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Percentage of employees' monthly salaries and wages as contributions to defined benefit plan.

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Percentage of monthly salary or wages as monthly contributions to defined contribution plan.

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