Retirement Benefit Plans - Maturity Analysis of Undiscounted Benefit Payments (Detail) $ in Millions	12 Months Ended
Dec. 31, 2019 TWD ($)
Disclosure Of Defined Benefit Plans [Abstract]
2020	$ 2,956
2021	7,261
2022	11,007
2023	12,756
2024 and thereafter	42,686
Total	$ 76,666

Estimated future benefit payments five fiscal years thereafter.

No definition available.

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