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Investments Accounted for Using Equity Method - Summary of Financial Information of Investments in Associates (Detail) $ in Millions, $ in Millions | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2020 TWD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 TWD ($) | Dec. 31, 2018 TWD ($) | Dec. 31, 2020 USD ($) | Nov. 30, 2019 | Feb. 28, 2019 | Dec. 31, 2017 TWD ($)
Condensed Financial Statements Captions [Line Items] |  |  |  |  |  |  |  |
Assets | $ 506,180 |  | $ 477,128 |  | $ 18,026 |  |  |
Liabilities | (118,907) |  | (92,856) |  | (4,235) |  |  |
Total equity | 387,273 |  | 384,272 | $ 384,529 | 13,791 |  |  | $ 382,124
Investments accounted for using equity method | 6,695 |  | 7,139 |  | $ 238 |  |  |
Revenues | 207,609 | $ 7,393 | 207,520 | 215,483 |  |  |  |
Net loss for the period | 34,704 | 1,236 | 33,921 | 38,581 |  |  |  |
Total other comprehensive income (loss), net of income tax | 1,290 | 46 | 1,328 | (1,014) |  |  |  |
TOTAL COMPREHENSIVE INCOME | 35,994 | $ 1,282 | 35,249 | $ 37,567 |  |  |  |
Next Commercial Bank Co., Ltd. (“NCB”) [Member] |  |  |  |  |  |  |  |
Condensed Financial Statements Captions [Line Items] |  |  |  |  |  |  |  |
Assets | 9,907 |  | 10,452 |  |  |  |  |
Liabilities | (789) |  | (728) |  |  |  |  |
Total equity | $ 9,118 |  | $ 9,724 |  |  |  |  |
Percentage of ownership in associates | 41.90% |  | 41.90% |  | 41.90% | 41.90% | 41.90% |
Equity attributable to the Company | $ 3,820 |  | $ 4,074 |  |  |  |  |
Unrealized gain or loss from downstream transactions | (43) |  |  |  |  |  |  |
Investments accounted for using equity method | 3,777 |  | 4,074 |  |  |  |  |
Net loss for the period | (605) |  | (276) |  |  |  |  |
TOTAL COMPREHENSIVE INCOME | $ (605) |  | $ (276) |  |  |  |  |

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