XML 146 R123.htm IDEA: XBRL DOCUMENT v3.21.1
Pensions - Defined Benefit Plans Amounts Recognized in Statements of Financial Position (Detail) - TWD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Surplus (deficit) in plan [abstract]        
Present value of defined benefit obligations $ (943,391) $ (901,159)    
Fair value of plan assets 431,740 421,052    
Net defined benefit liability $ (511,651) $ (480,107) $ (520,765) $ (478,526)