XML 195 R140.htm IDEA: XBRL DOCUMENT v3.20.1
Treasury Stock - Movement of Treasury Stock (Detail) - TWD ($)
shares in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Capital reduction   0
Capital reduction $ 1,284,223 $ 0
Ending balance $ 962,503  
Treasury stock [member]    
Treasury stock shares at beginning balance 30,085 30,085
Capital reduction (4,515)  
Treasury stock shares at ending balance 25,570 30,085
Beginning balance $ 1,007,654 $ 1,007,654
Capital reduction (45,151)  
Ending balance $ 962,503 $ 1,007,654