v3.26.1
Share-based Payment Arrangements - Summary of Information About ASE Inc. Option Plans (Detail) - The Company Option Plans [member]
$ / shares in Units, shares in Thousands
12 Months Ended
Dec. 31, 2025
shares
$ / shares
Dec. 31, 2024
shares
$ / shares
Dec. 31, 2023
TWD ($)
shares
$ / shares
Disclosure of terms and conditions of share-based payment arrangement [Line Items]      
Number of options, beginning balance | shares 188,101 212,240 81,262
Options granted | shares 0 0 150,000
Number of options, expired | shares (213) 0 0
Number of options, forfeited | shares (3,765) (5,873) (1,471)
Number of options, exercised | shares (32,981) (18,266) (17,551)
Number of options, Ending balance | shares 151,142 188,101 212,240
Number of options, exercisable, end of year | shares 66,837 44,242 62,505
Weighted average exercise price, Beginning balance | $ / shares $ 89.6 $ 89.1 $ 50.2
Options granted | $ / shares 0 0 107
Weighted average exercise price, Options expired | $ / shares 73 0 0
Weighted average exercise price, Options forfeited | $ / shares 93.5 103.7 66.9
Weighted average exercise price, Options exercised | $ / shares 79.1 48 50.9
Weighted average exercise price, Ending balance | $ / shares 87.8 89.6 89.1
Weighted average exercise price, Options exercisable, end of year | $ / shares $ 72.9 $ 44.3 $ 46.5
Bottom of range [member]      
Disclosure of terms and conditions of share-based payment arrangement [Line Items]      
Fair value of options granted (NT$) | $     $ 29.7
Top of range [member]      
Disclosure of terms and conditions of share-based payment arrangement [Line Items]      
Fair value of options granted (NT$) | $     $ 35.1