XML 194 R178.htm IDEA: XBRL DOCUMENT v3.21.1
Revenue - Summary of Changes in Contract Assets and Contract Liabilities (Detail) - TWD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Contract assets      
Net increase of customer contracts $ 5,972 $ 6,066 $ 4,126
Reclassified to trade receivables (5,681) (6,405) (7,532)
Significant changes of contract assets 291 (339) (3,406)
Contract liabilities      
Net increase of customer contracts 7 22 16
Recognized as revenues (30) (89) (194)
Significant changes of contract liabilities $ (23) $ (67) $ (178)