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Significant Contingent Liabilities and Unrecognized Commitments - Additional Information (Detail)
€ in Millions, $ in Millions, $ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2023
TWD ($)
Dec. 31, 2023
USD ($)
Dec. 31, 2023
EUR (€)
Dec. 31, 2023
SGD ($)
Dec. 31, 2022
TWD ($)
Dec. 31, 2021
TWD ($)
Aug. 15, 1996
TWD ($)
Commitments And Contingencies [Line Items]              
Unused letters of credit $ 10            
Prepayments 3,330 $ 109     $ 1,728    
Contract liabilities $ 14,088 $ 460     $ 13,390 $ 12,234  
Next Commercial Bank Co Ltd [Member]              
Commitments And Contingencies [Line Items]              
Ownership interest in associates 46.26%            
Singapore Telecommunications Limited [Member]              
Commitments And Contingencies [Line Items]              
Commitment amount     € 177 $ 51      
Prepayments | €     € 50        
Light Era Development Co Ltd [Member]              
Commitments And Contingencies [Line Items]              
Land presale contracts $ 4,244            
Contract liabilities $ 460            
Top of Range [Member] | Next Commercial Bank Co Ltd [Member]              
Commitments And Contingencies [Line Items]              
Ownership interest in associates 25.00%            
Piping Fund [Member]              
Commitments And Contingencies [Line Items]              
Commitment amount             $ 2,000
Commitment to contribute to a Piping Fund, amount contributed             $ 1,000
Commitment to contribute to a Piping Fund, remaining amount $ 1,000            
Land and buildings [Member]              
Commitments And Contingencies [Line Items]              
Commitments for acquisitions of property, plant and equipment 49            
Telecommunications equipment [Member]              
Commitments And Contingencies [Line Items]              
Commitments for acquisitions of property, plant and equipment $ 21,758