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Financial Instruments at Fair Value Through Profit or Loss - Summary of Financial Instruments at Fair Value through Profit or Loss (Detail) $ in Millions, $ in Millions | Dec. 31, 2020 TWD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 TWD ($)
--- | --- | --- | ---
Financial assets-current |  |  |
Financial assets-current, Mandatorily measured at FVTPL | $ 10 |  | $ 1
Financial assets-noncurrent |  |  |
Non-derivatives | 677 |  | 778
Financial liabilities-current |  |  |
Financial liabilities held for trading, Derivatives (not designated for hedge), Forward exchange contracts | 0 | $ 0 | 0
Forward exchange contracts [Member] |  |  |
Financial assets-current |  |  |
Derivatives (not designated for hedge) | 2 |  | 0
Listed stocks domestic [Member] |  |  |
Financial assets-current |  |  |
Non-derivatives | 8 |  | 1
Non listed stocks domestic [Member] |  |  |
Financial assets-noncurrent |  |  |
Non-derivatives | 441 |  | 511
Non listed stocks foreign [Member] |  |  |
Financial assets-noncurrent |  |  |
Non-derivatives | $ 236 |  | $ 267

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