XML 20 R1.htm IDEA: XBRL DOCUMENT v3.19.1
Document and Entity Information - shares
 12 Months Ended
Dec. 31, 2018
Jan. 31, 2019
Document and entity information [abstract]    
Document Type 20-F  
Amendment Flag false  
Document Period End Date Dec. 31, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus FY  
Trading Symbol ASX  
Entity Registrant Name ASE TECHNOLOGY HOLDING CO., LTD.  
Entity Central Index Key 0001122411  
Current Fiscal Year End Date --12-31  
Entity Well-known Seasoned Issuer Yes  
Entity Current Reporting Status Yes  
Entity Filer Category Large Accelerated Filer  
Entity Shell Company false  
Entity Emerging Growth Company false  
Entity Common Stock, Shares Outstanding   4,322,321,982