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Retirement Benefit Plans - Movements in Defined Benefit Obligation and Fair Value of Plan Assets (Detail)
$ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2024
TWD ($)
Dec. 31, 2024
USD ($)
Dec. 31, 2023
TWD ($)
Dec. 31, 2022
TWD ($)
Disclosure Of Defined Plan [line items]        
Net defined benefit liability (asset) at beginning of period $ (3,865)   $ (2,981) $ (1,103)
Current service cost 904   1,006 1,085
Loss on settlements     1  
Interest expense/interest income (50)   (49) (10)
Amounts recognized in profit or loss 854   958 1,075
Remeasurement on the net defined benefit liability        
Return on plan assets (excluding amounts included in net interest) (3,105)   (309) (2,968)
Actuarial (gains) losses recognized from changes in demographic assumptions (382)      
Actuarial (gains) losses recognized from changes in financial assumptions     (100) 208
Actuarial (gains) losses recognized from experience adjustments 1,232   252 1,606
Amounts recognized in other comprehensive income (2,255) $ (69) (157) (1,154)
Contributions from employer (1,245)   (1,386) (1,555)
Benefits paid 0   0 0
Settlement of plan obligation of subsidiaries 0      
Benefits paid directly by the Company (266)   (299) (244)
Net defined benefit liability (asset) at end of period (6,777)   (3,865) (2,981)
Present value of funded defined benefit obligation [Member]        
Disclosure Of Defined Plan [line items]        
Net defined benefit liability (asset) at beginning of period 30,313   33,599 35,502
Current service cost 904   1,006 1,085
Loss on settlements     1  
Interest expense/interest income 372   403 171
Amounts recognized in profit or loss 1,276   1,410 1,256
Remeasurement on the net defined benefit liability        
Return on plan assets (excluding amounts included in net interest) 0   0 0
Actuarial (gains) losses recognized from changes in demographic assumptions (382)      
Actuarial (gains) losses recognized from changes in financial assumptions     (100) 208
Actuarial (gains) losses recognized from experience adjustments 1,232   252 1,606
Amounts recognized in other comprehensive income 850   152 1,814
Contributions from employer 0   0 0
Benefits paid (4,188)   (4,549) (4,729)
Settlement of plan obligation of subsidiaries 0      
Benefits paid directly by the Company (266)   (299) (244)
Net defined benefit liability (asset) at end of period 27,985   30,313 33,599
Fair value of plan assets [Member]        
Disclosure Of Defined Plan [line items]        
Net defined benefit liability (asset) at beginning of period 34,178   36,580 36,605
Current service cost 0   0 0
Loss on settlements     0  
Interest expense/interest income 422   452 181
Amounts recognized in profit or loss 422   452 181
Remeasurement on the net defined benefit liability        
Return on plan assets (excluding amounts included in net interest) 3,105   309 2,968
Actuarial (gains) losses recognized from changes in demographic assumptions 0      
Actuarial (gains) losses recognized from changes in financial assumptions     0 0
Actuarial (gains) losses recognized from experience adjustments 0   0 0
Amounts recognized in other comprehensive income 3,105   309 2,968
Contributions from employer 1,245   1,386 1,555
Benefits paid (4,188)   (4,549) (4,729)
Settlement of plan obligation of subsidiaries 0      
Benefits paid directly by the Company 0   0 0
Net defined benefit liability (asset) at end of period $ 34,762   $ 34,178 $ 36,580