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Noncurrent Assets Held for Sale (Tables) | 12 Months Ended
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Dec. 31, 2020
Discontinued Operations and Disposal Groups [Abstract] |
Summary of Noncurrent Assets Held for Sale |
|  | December 31 |
|  | 2019 |  |  | 2020 |
|  | US$ |  |  | US$ |
Assets held for sale |  |  | 10,405 |  |  |  | 11,124 |
|  |  | 10,405 |  |  |  | 11,124 |

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