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Retirement Benefit Plans - Movements in Present Value of Defined Benefit Obligation (Detail) - TWD ($)
$ in Millions
12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Remeasurement:      
Actuarial loss arising from experience adjustments $ 1,413.8 $ 94.3 $ 494.1
Actuarial loss arising from changes in demographic assumptions   277.4  
Actuarial loss (gain) arising from changes in financial assumptions (160.8) (540.5) 3,161.9
Present value of defined benefit obligation [member]      
Disclosure of defined benefit plans [line items]      
Balance, beginning of year 16,585.5 16,980.3 13,484.1
Current service cost 134.3 145.3 123.3
Interest expense 120.8 66.7 118.8
Remeasurement:      
Actuarial loss arising from experience adjustments 1,413.8 94.3 494.1
Actuarial loss arising from changes in demographic assumptions   277.4  
Actuarial loss (gain) arising from changes in financial assumptions (160.8) (540.5) 3,161.9
Benefits paid from plan assets (585.3) (431.8) (399.0)
Benefits paid directly by the Company (24.3) (6.2) (2.9)
Balance, end of year $ 17,484.0 $ 16,585.5 $ 16,980.3