XML 179 R156.htm IDEA: XBRL DOCUMENT v3.21.1
Related Party Transactions - Summary of Purchases of Materials (Detail) - TWD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
JMC ELECTRONICS CO., LTD. [member]      
Disclosure of transactions between related parties [Line Items]      
Purchases of materials $ 0 $ 9 $ 132,494