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Equity Transaction with Non-controlling Interests - Additional Information (Detail) $ / shares in Units, $ / shares in Units, $ in Thousands, $ in Thousands |  |  |  | 1 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |
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Jul. 13, 2019 USD ($) | Jul. 01, 2019 | Jan. 01, 2018 shares | Jul. 31, 2019 USD ($) | May 31, 2019 TWD ($) shares | May 31, 2019 USD ($) shares | Aug. 31, 2018 USD ($) | Jul. 31, 2018 TWD ($) $ / shares | Jul. 31, 2018 TWD ($) $ / shares | Mar. 31, 2018 | Jan. 31, 2018 TWD ($) $ / shares | Jan. 31, 2017 TWD ($) | Dec. 31, 2019 TWD ($) shares | Dec. 31, 2019 USD ($) | Jul. 31, 2019 TWD ($) shares | Jul. 31, 2019 USD ($) shares | Jul. 13, 2019 TWD ($) | Dec. 31, 2018 TWD ($) | Aug. 31, 2018 TWD ($) | Jul. 31, 2018 USD ($) | May 31, 2018 USD ($) | Dec. 31, 2017 TWD ($)
Increase (decrease) in capital surplus |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 9,530 |  |  |
USI Enterprise Limited [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of increase in shareholdings |  | 95.42% | 96.90% | 98.72% |  |  |  |  |  |  | 98.60% |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in capital surplus |  |  |  |  |  |  |  |  |  |  | $ 1,127,632 |  |  |  | $ 1,625,448 | $ 54,345 |  |  |  |  |  |
Number of shares approved for repurchase | shares |  |  | 3,738,000 |  |  |  |  |  |  |  |  |  |  |  | 7,378,000 | 7,378,000 |  |  |  |  |  |
Shares repurchase price per share | $ / shares |  |  |  |  |  |  |  |  | $ 14.30 |  | $ 17.49 |  |  |  |  |  |  |  |  |  |  |
USI [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of increase in shareholdings |  |  |  |  |  |  |  |  |  |  |  | 75.20% |  |  |  |  |  |  |  |  |  |
Increase (decrease) in capital surplus |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 3,055
Cash capital increase amount |  |  |  |  |  |  |  |  |  |  |  | $ 1,000,000 |  |  |  |  |  |  |  |  |  |
Ordinary shares outstanding acquired price | $ / shares |  |  |  |  |  |  |  | $ 18 |  |  |  |  |  |  |  |  |  |  |  |  |  |
USI [member] | Cash capital increase [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of increase in shareholdings |  |  |  |  |  |  |  |  |  |  |  | 75.70% |  |  |  |  |  |  |  |  |  |
ASEN [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in capital surplus |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,650,950 | $ 88,631 |  | $ 622,811 |  |  |  |
Amount of shares transferred |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 127,113 |
Percentage of shareholdings |  |  |  | 30.00% |  |  | 30.00% |  |  | 40.00% |  |  |  |  |  |  |  |  |  |  |  |
Amount of shareholdings |  |  |  | $ 97,748 |  |  | $ 95,335 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ASEN [member] | Bottom of range [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of increase in ownership |  |  |  | 70.00% |  |  |  |  |  | 60.00% |  |  |  |  |  |  |  |  |  |  |  |
ASEN [member] | Top of range [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of increase in ownership |  |  |  | 100.00% |  |  |  |  |  | 70.00% |  |  |  |  |  |  |  |  |  |  |  |
USI INC [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in capital surplus |  |  |  |  |  |  |  | $ 142 | $ 142 |  |  |  |  |  |  |  |  |  | $ 28,152 | $ 5 |  |
Ordinary shares outstanding acquired price | $ / shares |  |  |  |  |  |  |  | $ 35 |  |  |  |  |  |  |  |  |  |  |  |  |  |
USISH [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of shares repurchased | shares |  |  |  |  |  |  |  |  |  |  |  |  | 13,037 |  |  |  |  |  |  |  |  |
Increase (decrease) in capital surplus |  |  |  |  |  |  |  |  |  |  |  |  | $ 334,719 | $ 11,191 |  |  |  |  |  |  |  |
USISH [Member] | Bottom of range [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of increase in shareholdings |  |  |  |  |  |  |  |  |  |  |  |  | 74.60% |  |  |  |  |  |  |  |  |
USISH [Member] | Top of range [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of increase in shareholdings |  |  |  |  |  |  |  |  |  |  |  |  | 77.70% |  |  |  |  |  |  |  |  |
ASEEE [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in capital surplus |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,306 | $ 128,805 |  |  |  |  |
Percentage of ShareHolding Held |  |  |  | 100.00% |  |  |  |  |  |  |  |  | 100.00% |  |  |  |  |  |  |  |  |
Purchase of ordinary share held | $ 6,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ASEEE [member] | Ordinary shares [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchased Ordinary Shares | shares |  |  |  |  | 150,000 | 150,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ASEEE [member] | Cash capital increase [member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash capital increase amount |  |  |  |  | $ 1,500,000 | $ 50,150 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
SZ [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of shareholdings |  |  |  | 30.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase of Acquisition |  |  |  | $ 162,870 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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