Retirement Benefit Plans - Movements in Fair Value of Plan Assets (Detail) - Fair value of plan assets [member] - TWD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2023 |
Dec. 31, 2022 |
Dec. 31, 2021 |
|
| Disclosure of fair value of plan assets [line items] | |||
| Balance, beginning of year | $ 8,162.9 | $ 5,548.6 | $ 5,066.2 |
| Interest income | 161.7 | 46.5 | 19.5 |
| Remeasurement: | |||
| Return on plan assets (excluding amounts included in net interest expense) | 16.2 | 429.9 | 73.3 |
| Contributions from employer | 953.6 | 2,723.2 | 821.4 |
| Benefits paid from plan assets | (556.5) | (585.3) | (431.8) |
| Balance, end of year | $ 8,737.9 | $ 8,162.9 | $ 5,548.6 |