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Segment Information - Financial Segment Information for Operating Segments (Detail) $ in Thousands, $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 TWD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 TWD ($) | Dec. 31, 2017 TWD ($)
Revenue |  |  |  |
Revenue | $ 20,337,881 | $ 679,969 | $ 18,480,027 | $ 17,940,855
Operating profit (loss) | 2,457,119 | 82,150 | 2,099,721 | 2,239,881
Interest expense | (171,075) |  | (152,416) | (190,425)
Share of profit (loss) of associates | (154,926) | $ (5,179) | (300,101) | (179,491)
Purchase of property, plant and equipment | 4,896,656 |  | 4,945,570 |
Continuing operations [member] |  |  |  |
Revenue |  |  |  |
Revenue | 20,337,881 |  | 18,480,027 | 17,940,855
Operating profit (loss) | 2,457,119 |  | 2,099,721 | 2,239,881
Depreciation expenses | (3,731,914) |  | (3,376,579) | (2,899,278)
Interest income | 64,368 |  | 49,971 | 53,123
Interest expense | (171,075) |  | (152,416) | (190,425)
Share of profit (loss) of associates | (154,926) |  | (300,101) | (179,491)
Purchase of property, plant and equipment | 4,896,656 |  | 4,945,570 | 4,702,691
Continuing operations [member] | External [member] |  |  |  |
Revenue |  |  |  |
Revenue | 20,337,881 |  | 18,480,027 | 17,940,855
Continuing operations [member] | Operating segments [member] | Testing [member] |  |  |  |
Revenue |  |  |  |
Revenue | 4,257,800 |  | 4,790,097 | 4,838,246
Operating profit (loss) | 709,142 |  | 1,306,742 | 1,448,939
Depreciation expenses | (802,740) |  | (769,660) | (673,393)
Purchase of property, plant and equipment | 764,105 |  | 1,563,919 | 836,894
Continuing operations [member] | Operating segments [member] | Testing [member] | External [member] |  |  |  |
Revenue |  |  |  |
Revenue | 4,257,800 |  | 4,790,097 | 4,838,246
Continuing operations [member] | Operating segments [member] | Assembly [member] |  |  |  |
Revenue |  |  |  |
Revenue | 5,148,877 |  | 4,679,676 | 5,259,281
Operating profit (loss) | (227,096) |  | (207,700) | (55,198)
Depreciation expenses | (521,311) |  | (578,205) | (597,500)
Purchase of property, plant and equipment | 548,063 |  | 321,976 | 655,879
Continuing operations [member] | Operating segments [member] | Assembly [member] | External [member] |  |  |  |
Revenue |  |  |  |
Revenue | 5,148,877 |  | 4,679,676 | 5,259,281
Continuing operations [member] | Operating segments [member] | LCDD [member] |  |  |  |
Revenue |  |  |  |
Revenue | 6,922,205 |  | 5,694,720 | 4,790,116
Operating profit (loss) | 1,740,720 |  | 1,226,755 | 1,285,495
Depreciation expenses | (1,796,951) |  | (1,400,784) | (1,048,587)
Purchase of property, plant and equipment | 3,077,806 |  | 2,732,141 | 2,615,153
Continuing operations [member] | Operating segments [member] | LCDD [member] | External [member] |  |  |  |
Revenue |  |  |  |
Revenue | 6,922,205 |  | 5,694,720 | 4,789,869
Continuing operations [member] | Operating segments [member] | LCDD [member] | Intersegment [member] |  |  |  |
Revenue |  |  |  |
Revenue |  |  |  | 247
Continuing operations [member] | Operating segments [member] | Bumping [member] |  |  |  |
Revenue |  |  |  |
Revenue | 4,008,999 |  | 3,315,534 | 3,053,459
Operating profit (loss) | 232,404 |  | (202,497) | (336,123)
Depreciation expenses | (604,553) |  | (627,412) | (579,605)
Purchase of property, plant and equipment | 506,635 |  | 327,251 | 594,765
Continuing operations [member] | Operating segments [member] | Bumping [member] | External [member] |  |  |  |
Revenue |  |  |  |
Revenue | 4,008,999 |  | 3,315,534 | 3,053,459
Continuing operations [member] | Operating segments [member] | Others [member] |  |  |  |
Revenue |  |  |  |
Revenue | 32,808 |  | 35,738 | 35,808
Operating profit (loss) | 1,931 |  | (23,433) | (100,545)
Depreciation expenses | (6,359) |  | (518) | (503)
Interest income | 64,368 |  | 49,971 | 53,123
Interest expense | (171,075) |  | (152,416) | (190,425)
Share of profit (loss) of associates | (370,351) |  | (668,377) | 1,347,851
Purchase of property, plant and equipment | 47 |  | 283 |
Continuing operations [member] | Operating segments [member] | Others [member] | Intersegment [member] |  |  |  |
Revenue |  |  |  |
Revenue | 32,808 |  | 35,738 | 35,808
Continuing operations [member] | Elimination [member] |  |  |  |
Revenue |  |  |  |
Revenue | (32,808) |  | (35,738) | (36,055)
Operating profit (loss) | 18 |  | (146) | (2,687)
Depreciation expenses |  |  |  | 310
Share of profit (loss) of associates | 215,425 |  | 368,276 | (1,527,342)
Continuing operations [member] | Elimination [member] | Intersegment [member] |  |  |  |
Revenue |  |  |  |
Revenue | $ (32,808) |  | $ (35,738) | (36,055)
Discontinued operations: Unimos Shanghai [member] |  |  |  |
Revenue |  |  |  |
Revenue |  |  |  | 227,095
Operating profit (loss) |  |  |  | (25,394)
Interest income |  |  |  | 464
Interest expense |  |  |  | (2,414)
Discontinued operations: Unimos Shanghai [member] | External [member] |  |  |  |
Revenue |  |  |  |
Revenue |  |  |  | $ 227,095

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