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Hedging Financial Instruments - Summary of Hedging Instrument (Details) - Forecast Purchases - forward Exchange Contract [Member] - Cash flow hedges [member]
€ in Millions, $ in Millions
 12 Months Ended
Dec. 31, 2021
TWD ($)
Dec. 31, 2020
TWD ($)
Dec. 31, 2019
TWD ($)
Dec. 31, 2021
EUR (€)
Dec. 31, 2020
EUR (€)
Dec. 31, 2019
EUR (€)
Disclosure Of Detailed Information About Hedging Instruments [Line Items]            
Change in Value of Hedged Item Used for Calculating Hedge Ineffectiveness $ 10 $ (2) $ 1      
Accumulated Gain or Loss on Hedging Instruments in Other Equity Continuing Hedges (8) 2 0      
Accumulated Gain or Loss on Hedging Instruments in Other Equity Hedge Accounting No Longer Applied $ 0 $ 0 $ 0      
Foreign currency risk [Member]            
Disclosure Of Detailed Information About Hedging Instruments [Line Items]            
Currency NT$/EUR NT$/EUR NT$/EUR      
Contract Amount $ 228 $ 201 $ 84 € 7 € 6 € 2
Maturity Period 2022.03 2021.03 2020.03      
Forward Rate 32.54 34.45 33.66      
Carrying Amount of Asset $ 0 $ 2 $ 0      
Carrying Amount of Liability 8 0 0      
Change in Fair Values of Hedging Instruments Used for Calculating Hedge Ineffectiveness $ (10) $ 2 $ (1)