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Trade Notes and Accounts Receivable, Net - Movements of Allowance for Doubtful Accounts, Trade Notes and Accounts Receivable (Detail) - TWD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Disclosure Of Financial Assets [Line Items]      
Beginning balance $ 2,154    
Add: Provision for credit loss 123 $ 49 $ (54)
Ending balance 1,605 2,154  
Trade notes and accounts receivable [Member]      
Disclosure Of Financial Assets [Line Items]      
Beginning balance 2,154 2,360  
Add: Provision for credit loss 123 49  
Add: Acquired by business combinations (Note 14)   2  
Less: Amounts written off (672) (257)  
Ending balance $ 1,605 $ 2,154 $ 2,360