v3.26.1
Financial Risk and Fair Value Disclosures - Maturity Profile of Financial Liabilities Based on Contractual Undiscounted Payments and Contractual Maturity (Parenthetical) (Detail) - TWD ($)
$ in Millions
 4 Months Ended
Apr. 30, 2026
Dec. 31, 2025
Dec. 31, 2024
Disclosure Of Maturity Analysis For Non-derivative And Derivative Financial Liabilities [Line Items]      
Investments in equity instruments designated at fair value through other comprehensive income   $ 4,630 $ 5,893
Non Adjusting Events After Reporting Period [member]      
Disclosure Of Maturity Analysis For Non-derivative And Derivative Financial Liabilities [Line Items]      
Total amount of repayments of the long-term loans which were classified as non-current liabilities $ 1,839    
2 to 3 years [member] | Non Adjusting Events After Reporting Period [member]      
Disclosure Of Maturity Analysis For Non-derivative And Derivative Financial Liabilities [Line Items]      
Total amount of repayments of the long-term loans which were classified as non-current liabilities 1,039    
4 to 5 years [member] | Non Adjusting Events After Reporting Period [member]      
Disclosure Of Maturity Analysis For Non-derivative And Derivative Financial Liabilities [Line Items]      
Total amount of repayments of the long-term loans which were classified as non-current liabilities $ 800