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Long Term Loans - Summary of Long-term Loans (Detail)
$ in Millions, $ in Millions
Dec. 31, 2020
TWD ($)
Dec. 31, 2020
USD ($)
Dec. 31, 2019
TWD ($)
Disclosure of detailed information about borrowings [Line Items]      
Less: Current portion $ (1,600) $ (57) $ 0
Non-current portion of non-current borrowings 0 $ 0 1,600
Long-term loans [Member]      
Disclosure of detailed information about borrowings [Line Items]      
Secured loans 1,600   1,600
Less: Current portion $ (1,600)    
Non-current portion of non-current borrowings     $ 1,600
Long-term loans [Member] | Secured loans [Member]      
Disclosure of detailed information about borrowings [Line Items]      
Interest rates of loans 0.72% 0.72% 0.92%