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Significant Related Party Transactions - Significant Intercompany Transactions Between Consolidated Entities (Detail) $ in Thousands, $ in Millions |  | 8 Months Ended | 12 Months Ended
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Apr. 02, 2024 | Aug. 31, 2024 TWD ($) | Dec. 31, 2024 TWD ($) | Dec. 31, 2024 USD ($) | Dec. 31, 2023 TWD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2022 TWD ($) | Dec. 31, 2022 USD ($)
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Amount of downstream transaction |  |  |  | $ 350 |  | $ 350 |  | $ 350
Disposal of proportion of ownership interest in subsidiary | 100.00% | 100.00% |  |  |  |  |  |
UMC GROUP (USA) [member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  |  | $ 58,145,772 |  | $ 61,923,652 |  | $ 68,554,072 |
Accounts receivable |  |  | $ 6,970,670 |  | $ 5,827,800 |  | $ 9,502,922 |
Explanation of terms and conditions of outstanding balances for related party transaction |  |  | Net 60 days | Net 60 days | Net 60 days | Net 60 days | Net 60 days | Net 60 days
UNITED SEMICONDUCTOR (XIAMEN) CO., LTD. (USCXM) [member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  |  | $ 1,210,478 |  | $ 1,127,275 |  | $ 1,143,280 |
Accounts receivable |  |  | $ 12,623 |  | $ 11,688 |  | $ 16,774 |
Explanation of terms and conditions of outstanding balances for related party transaction |  |  | Net 30 days | Net 30 days | Net 30 days | Net 30 days | Net 30 days | Net 30 days
UNITEDDS SEMICONDUCTOR (SHANDONG) CO., LTD. (UDS) [member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  | $ 337,007 |  |  | $ 364,948 |  | $ 656,472 |
Accounts receivable |  |  |  |  | $ 10,800 |  | $ 6,734 |
Explanation of terms and conditions of outstanding balances for related party transaction |  | Net 30 days |  |  | Net 30 days | Net 30 days | Net 30 days | Net 30 days
UNITED SEMICONDUCTOR JAPAN CO., LTD. (USJC) [member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  |  |  |  |  |  | $ 164,855 |
Accounts receivable |  |  |  |  |  |  | $ 151,430 |
Explanation of terms and conditions of outstanding balances for related party transaction |  |  |  |  |  |  | Net 60 days | Net 60 days
UNITED SEMICONDUCTOR JAPAN CO., LTD. (USJC) [member] | UMC GROUP (USA) [member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  |  | $ 4,755,322 |  | $ 3,487,292 |  | $ 4,272,900 |
Accounts receivable |  |  | $ 713,962 |  | $ 342,835 |  | $ 744,082 |
Explanation of terms and conditions of outstanding balances for related party transaction |  |  | Net 60 days | Net 60 days | Net 60 days | Net 60 days | Net 60 days | Net 60 days
UNITED SEMICONDUCTOR (XIAMEN) CO., LTD. (USCXM) [member] | UMC GROUP (USA) [member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  |  | $ 639,413 |  | $ 1,208,630 |  | $ 1,565,670 |
Accounts receivable |  |  | $ 137,666 |  | $ 17,816 |  | $ 310,431 |
Explanation of terms and conditions of outstanding balances for related party transaction |  |  | Net 60 days | Net 60 days | Net 60 days | Net 60 days | Net 60 days | Net 60 days
UNITED SEMICONDUCTOR (XIAMEN) CO., LTD. (USCXM) [member] | UNITEDDS SEMICONDUCTOR (SHANDONG) CO., LTD. (UDS) [member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  | $ 287,522 |  |  | $ 286,087 |  | $ 148,259 |
Accounts receivable |  |  |  |  | $ 362 |  | $ 171 |
Explanation of terms and conditions of outstanding balances for related party transaction |  | Month-end 30 days |  |  | Month-end 30 days | Month-end 30 days | Month-end 30 days | Month-end 30 days
UNITED SEMICONDUCTOR (XIAMEN) CO., LTD. (USCXM) [member] | UMC [Member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  |  |  |  | $ 134,303 |  | $ 1,035,407 |
Accounts receivable |  |  |  |  |  |  | $ 173 |
Explanation of terms and conditions of outstanding balances for related party transaction |  |  |  |  | Net 30 days - Net 45 days | Net 30 days - Net 45 days | Net 30 days - Net 45 days | Net 30 days - Net 45 days
WAVETEK MICROELECTRONICS CORPORATION (WAVETEK) (WTK) [member] | UMC GROUP (USA) [member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  |  | $ 397,260 |  | $ 505,806 |  | $ 716,357 |
Accounts receivable |  |  | $ 39,086 |  | $ 53,916 |  | $ 81,819 |
Explanation of terms and conditions of outstanding balances for related party transaction |  |  | Net 60 days | Net 60 days | Net 60 days | Net 60 days | Net 60 days | Net 60 days
WAVETEK MICROELECTRONICS CORPORATION (WAVETEK) (WTK) [member] | UMC [Member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  |  |  |  |  |  | $ 124,178 |
Explanation of terms and conditions of outstanding balances for related party transaction |  |  |  |  |  |  | Month-end 30 days | Month-end 30 days
HEJIAN TECHNOLOGY (SUZHOU) CO., LTD. (HJ) [member] | UMC GROUP (USA) [member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  |  | $ 240,749 |  | $ 384,067 |  | $ 551,913 |
Accounts receivable |  |  | $ 31,132 |  | $ 43,863 |  | $ 147,265 |
Explanation of terms and conditions of outstanding balances for related party transaction |  |  | Net 60 days | Net 60 days | Net 60 days | Net 60 days | Net 60 days | Net 60 days
HEJIAN TECHNOLOGY (SUZHOU) CO., LTD. (HJ) [member] | UDS [Member] |  |  |  |  |  |  |  |
Disclosure of transactions between related parties [line items] |  |  |  |  |  |  |  |
Sales |  |  |  |  | $ 159,523 |  | $ 311,972 |
Accounts receivable |  |  |  |  | $ 2,696 |  | $ 9,500 |
Explanation of terms and conditions of outstanding balances for related party transaction |  |  |  |  | Month-end 30 days | Month-end 30 days | Month-end 30 days | Month-end 30 days

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