v3.26.1
Contents of Significant Accounts - Summary of Fair Value of Each Investment in Equity Instrument (Detail) - TWD ($)
$ in Thousands
Dec. 31, 2025
Dec. 31, 2024
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]    
Fair value of investments in equity instruments $ 4,630,000 $ 5,893,000
UNIMICRON HOLDING LIMITED [member]    
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]    
Fair value of investments in equity instruments 1,973,011 2,474,388
ITE TECH. INC. [member]    
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]    
Fair value of investments in equity instruments 1,605,398 2,093,997
CHIPBOND TECHNOLOGY CORPORATION [member]    
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]    
Fair value of investments in equity instruments 2,865,530 3,423,750
NOVATEK MICROELECTRONICS CORP. (NOVATEK) [member]    
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]    
Fair value of investments in equity instruments 6,150,275 8,255,183
KAI-HONG ENERGY CO., LTD. [Member]    
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]    
Fair value of investments in equity instruments 67,347 64,865
SHIN-ETSU HANDOTAI TAIWAN CO., LTD. [member]    
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]    
Fair value of investments in equity instruments 762,930 692,265
TAIWAN SMART ELECTRICITY & ENERGY CO., LTD.    
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]    
Fair value of investments in equity instruments 147,450 0
MTIC HOLDINGS PTE. LTD. [member]    
Disclosure of fair value of investments in equity instruments designated at fair value through other comprehensive income [line items]    
Fair value of investments in equity instruments $ 202,808 $ 204,880