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Hedging Financial Instruments - Summary of Information Relating to Hedges for Foreign Currency Risk (Detail)
$ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2021
TWD ($)
Dec. 31, 2021
USD ($)
Dec. 31, 2020
TWD ($)
Dec. 31, 2019
TWD ($)
Dec. 31, 2021
USD ($)
Disclosure of detailed information about financial instruments [line items]          
Increase (Decrease) in Value Used for Calculating Hedge Ineffectiveness $ (41.4) $ (1.5) $ 24.1 $ (109.6)  
Cash flow hedges [member]          
Disclosure of detailed information about financial instruments [line items]          
Increase (Decrease) in Value Used for Calculating Hedge Ineffectiveness (41.4)   24.1 (109.6)  
Cash flow hedges [member] | Forecast Transaction Capital Expenditures [member]          
Disclosure of detailed information about financial instruments [line items]          
Increase (Decrease) in Value Used for Calculating Hedge Ineffectiveness 41.4   $ (24.1) $ 109.6  
Cash flow hedges [member] | Forecast Transaction Relates To Issuance of Debts [Member]          
Disclosure of detailed information about financial instruments [line items]          
Increase (Decrease) in Value Used for Calculating Hedge Ineffectiveness (132.5)        
Cash flow hedges [member] | Forward interest rate contracts          
Disclosure of detailed information about financial instruments [line items]          
Maturity     January 2022    
Cash flow hedges [member] | Forward interest rate contracts | Interest rate risk [member]          
Disclosure of detailed information about financial instruments [line items]          
Contract Amount         $ 328.0
Balance in Other Equity (Continuing Hedges) 128.2        
Cash flow hedges [member] | Forward interest rate contracts | Forecast Transaction Relates To Issuance of Debts [Member]          
Disclosure of detailed information about financial instruments [line items]          
Increase (Decrease) in Value Used for Calculating Hedge Ineffectiveness $ 132.5