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Investments Accounted for Using Equity Method - Investments in Joint Ventures (Detail)
$ in Millions, $ in Millions
12 Months Ended
Dec. 31, 2021
TWD ($)
Dec. 31, 2021
USD ($)
Dec. 31, 2020
TWD ($)
Dec. 31, 2019
TWD ($)
Disclosure Of Joint Ventures [Line Items]        
Investment in joint venture $ 10   $ 10  
The Company’s share of profits 421 $ 15 244 $ 459
Joint ventures [Member] | Chunghwa SEA Holdings (“CHT SEA”) [Member]        
Disclosure Of Joint Ventures [Line Items]        
Investment in joint venture $ 10   $ 10  
Percentage of ownership in joint venture 51.00% 51.00% 51.00%