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Intangible Assets - Additional Information (Detail) - TWD ($)
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Certain licensed contract [Member]      
Disclosure of detailed information about intangible assets [Line Items]      
Impairment loss $ 0 $ 0  
Senao Networks, Inc. ("SNI") [Member] | Certain licensed contract [Member]      
Disclosure of detailed information about intangible assets [Line Items]      
Impairment loss     $ 9,000,000
Asia Pacific Telecom Co., Ltd [Member] | Intangible Assets- Mobile Broadband Concession and Other Assets- Spare Parts [Member]      
Disclosure of detailed information about intangible assets [Line Items]      
Tax-excluded transaction amount $ 1,800,000,000    
Bottom of range [Member] | Computer software [Member]      
Disclosure of detailed information about intangible assets [Line Items]      
Estimated useful lives 1 year    
Bottom of range [Member] | Others [Member]      
Disclosure of detailed information about intangible assets [Line Items]      
Estimated useful lives 3 years    
Top of Range [Member] | Computer software [Member]      
Disclosure of detailed information about intangible assets [Line Items]      
Estimated useful lives 10 years    
Top of Range [Member] | Others [Member]      
Disclosure of detailed information about intangible assets [Line Items]      
Estimated useful lives 20 years