Contents of Significant Accounts - Share-Based Payment - Additional Information (Detail) $ in Thousands, Right in Millions |
1 Months Ended | 9 Months Ended | 12 Months Ended | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Dec. 05, 2025 |
Dec. 05, 2024 |
Dec. 05, 2023 |
Dec. 05, 2022 |
Jun. 09, 2021 |
Sep. 30, 2020 |
Sep. 01, 2020 |
Jun. 30, 2021
Right
|
Sep. 30, 2020
Right
|
Dec. 31, 2025
TWD ($)
|
Dec. 31, 2024
TWD ($)
|
Dec. 31, 2023
TWD ($)
|
|
| Restricted Stock Plan For Employees [Member] | ||||||||||||
| Disclosure of terms and conditions of share-based payment arrangement [line items] | ||||||||||||
| Compensation expenses | $ | $ 483,000 | $ 775,000 | $ 1,025,000 | |||||||||
| Eligibility terms to vested restricted stocks | Beginning from the end of two years since the date of grant, those employees who fulfill both service period and performance conditions set by UMC are gradually eligible to the vested restricted stocks at certain percentage and time frame. | |||||||||||
| Life of plan | 4 years | 4 years | 4 years | 4 years | 4 years | 4 years | ||||||
| Stock Appreciation Right Plan For Employees [Member] | ||||||||||||
| Disclosure of terms and conditions of share-based payment arrangement [line items] | ||||||||||||
| Compensation expenses | $ | $ 1,000 | 20,000 | $ 105,000 | |||||||||
| Stock Appreciation Right Plan For Employees Description | One unit of stock appreciation right to employees represents a right to the intrinsic value of one common share of UMC. | |||||||||||
| Life of plan | 4 years | 4 years | ||||||||||
| Liabilities for stock appreciation right recognized | $ 0 | 8,000 | ||||||||||
| Unit of cash-settled stock appreciation right | Right | 1 | 26 | ||||||||||
| Intrinsic Value for the Liabilities of Vested Rights | $ 0 | $ 0 | ||||||||||