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Revenue - Summary of Revenue (Detail)
$ in Millions, $ in Millions
12 Months Ended
Dec. 31, 2019
TWD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
TWD ($)
Dec. 31, 2017
TWD ($)
Revenue [Abstract]        
Revenue from contracts with customers $ 206,360   $ 214,461  
Other revenues        
Rental income 818   640  
Other 342   382  
Revenue other than from contracts with customers 1,160   1,022  
Total $ 207,520 $ 6,938 $ 215,483 $ 227,514