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Trade Notes and Accounts Receivable, Net - Summary of Trade Notes and Accounts Receivable, Net (Detail)
$ in Millions, $ in Millions
Dec. 31, 2017
TWD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
TWD ($)
Disclosure of financial assets [Line Items]      
Trade notes and accounts receivable $ 31,941 $ 1,077 $ 31,022
Gross carrying amount [Member]      
Disclosure of financial assets [Line Items]      
Trade notes and accounts receivable 34,058   32,795
Allowance for doubtful accounts [Member]      
Disclosure of financial assets [Line Items]      
Trade notes and accounts receivable $ (2,117)   $ (1,773)