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v3.20.1

Treasury Stock - Movement of Treasury Stock (Detail) - TWD ($) shares in Thousands, $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017
Capital reduction |  | 0
Capital reduction | $ 1,284,223 | $ 0
Ending balance | $ 962,503 |
Treasury stock [member] |  |
Treasury stock shares at beginning balance | 30,085 | 30,085
Capital reduction | (4,515) |
Treasury stock shares at ending balance | 25,570 | 30,085
Beginning balance | $ 1,007,654 | $ 1,007,654
Capital reduction | (45,151) |
Ending balance | $ 962,503 | $ 1,007,654

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