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Contents of Significant Accounts - Summary of Assumptions Used for Compensation Cost for Cash-settled Share-based Payment Measured at Fair Value on Grant Date by using Black-Scholes Option Pricing Model (Detail) - Stock Appreciation Right Plan For Employees [Member]
 12 Months Ended
Dec. 31, 2023
yr
$ / shares
Granted in September 2020 [Member]  
Statement [Line Items]  
Share price of measurement date (NT$/ per share) | $ / shares $ 52.6
Expected volatility 23.95%
Expected life 0.67
Expected dividend yield 6.02%
Risk-free interest rate 1.06%
Granted in June 2021 [Member]  
Statement [Line Items]  
Share price of measurement date (NT$/ per share) | $ / shares $ 52.6
Expected dividend yield 6.02%
Bottom of range [member] | Granted in June 2021 [Member]  
Statement [Line Items]  
Expected volatility 23.21%
Expected life 0.44
Risk-free interest rate 1.06%
Top of range [member] | Granted in June 2021 [Member]  
Statement [Line Items]  
Expected volatility 28.72%
Expected life 1.44
Risk-free interest rate 1.08%