v3.26.1
Retirement Benefit Plans - Summary of Movements in Net Defined Benefit Liability (Detail)
$ in Thousands, $ in Thousands
 12 Months Ended
Dec. 31, 2025
TWD ($)
Dec. 31, 2025
USD ($)
Dec. 31, 2024
TWD ($)
Dec. 31, 2023
TWD ($)
Disclosure of net defined benefit liability (asset) [line items]        
Beginning balance $ 2,869,587 $ 91,476 $ 3,584,736 $ 3,784,120
Current service cost 131,232 4,183 139,168 126,956
Past service cost and loss on settlements 5,412 173 274 1,194
Net interest expense (income) 60,251 1,921 61,559 62,108
Other termination benefit cost       7,822
Recognized in profit or loss 196,895 6,277 201,001 198,080
Return on plan assets (excluding amounts included in net interest) (379,292) (12,091) (437,258) (9,327)
Changes in financial assumptions 47,483 1,514 (46,189) 391,077
Experience adjustments 1,579,901 50,363 249,911 (309,843)
Changes in demographic assumptions (7,700) (246) (16,009) (6,476)
Recognized in other comprehensive income 1,240,392 39,540 (249,545) 65,431
Contributions from the employer (584,566) (18,635) (646,687) (597,870)
Benefits paid from the pension fund 0 0 0 (5,402)
Benefits paid from the Group (76,194) (2,429) (124,601) (79,659)
Liabilities extinguished on settlements (4,307) (137) (5,270) (2,830)
Liabilities assumed in a business combination     158,053 204,975
Exchange differences on foreign plans (29,782) (949) (48,100) 17,891
Ending balance 3,612,025 115,143 2,869,587 3,584,736
Defined benefit obligation [member]        
Disclosure of net defined benefit liability (asset) [line items]        
Beginning balance 10,123,897 322,725 10,201,794 10,261,997
Current service cost 131,232 4,183 139,168 126,956
Past service cost and loss on settlements 5,412 173 274 1,194
Net interest expense (income) 217,768 6,942 205,562 236,102
Other termination benefit cost       7,822
Recognized in profit or loss 354,412 11,298 345,004 372,074
Return on plan assets (excluding amounts included in net interest) 0 0 0 0
Changes in financial assumptions 47,483 1,514 (46,189) 391,077
Experience adjustments 1,579,901 50,363 249,911 (309,843)
Changes in demographic assumptions (7,700) (246) (16,009) (6,476)
Recognized in other comprehensive income 1,619,684 51,631 187,713 74,758
Contributions from the employer 0 0 0 0
Benefits paid from the pension fund (610,507) (19,461) (539,124) (615,377)
Benefits paid from the Group (76,194) (2,429) (124,601) (79,659)
Liabilities extinguished on settlements (4,307) (137) (5,836) (2,830)
Liabilities assumed in a business combination     158,053 204,975
Exchange differences on foreign plans 24,185 771 (99,106) (14,144)
Ending balance 11,431,170 364,398 10,123,897 10,201,794
Fair value of plan assets [member]        
Disclosure of net defined benefit liability (asset) [line items]        
Beginning balance (7,254,310) (231,249) (6,617,058) (6,477,877)
Current service cost 0 0 0 0
Past service cost and loss on settlements 0 0 0 0
Net interest expense (income) (157,517) (5,021) (144,003) (173,994)
Other termination benefit cost       0
Recognized in profit or loss (157,517) (5,021) (144,003) (173,994)
Return on plan assets (excluding amounts included in net interest) (379,292) (12,091) (437,258) (9,327)
Changes in financial assumptions 0 0 0 0
Experience adjustments 0 0   0
Changes in demographic assumptions 0 0 0 0
Recognized in other comprehensive income (379,292) (12,091) (437,258) (9,327)
Contributions from the employer (584,566) (18,635) (646,687) (597,870)
Benefits paid from the pension fund 610,507 19,461 539,124 609,975
Benefits paid from the Group 0 0 0 0
Liabilities extinguished on settlements 0 0 566 0
Liabilities assumed in a business combination     0 0
Exchange differences on foreign plans (53,967) (1,720) 51,006 32,035
Ending balance $ (7,819,145) $ (249,255) $ (7,254,310) $ (6,617,058)