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Summary of Significant Accounting Policies - Summary of Subsidiaries (Detail)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
The Company [Member] | ASE [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 100.00% 100.00%
The Company [Member] | USIINC [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 100.00% 100.00%
The Company [Member] | SPIL [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the assembly, testing and turnkey services of integrated circuit  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 100.00% 100.00%
ASE [Member] | ASE Holding Limited [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Bermuda  
Percentage of Ownership (%) 100.00% 100.00%
ASE [Member] | J & R Holding Limited ("J&R Holding") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Bermuda  
Percentage of Ownership (%) 100.00% 100.00%
ASE [Member] | Innosource Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location British Virgin Islands  
Percentage of Ownership (%) 100.00% 100.00%
ASE [Member] | Omniquest Industrial Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location British Virgin Islands  
Percentage of Ownership (%) 71.00% 71.00%
ASE [Member] | ASE Marketing & Service Japan Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in marketing and sales services  
Establishment and Operating Location Japan  
Percentage of Ownership (%) 100.00% 100.00%
ASE [Member] | ASE Test, Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the testing of semiconductors  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 100.00% 100.00%
ASE [Member] | Luchu Development Corporation [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the development of real estate properties  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 67.10% 67.10%
ASE [Member] | ASEEE [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Merged into ASE in February 2020  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 0.00% 100.00%
ASE [Member] | Advanced Microelectronic Products Inc. ("AMPI") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the manufacturing of integrated circuit  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 7.60% 7.60%
ASE Test Inc [Member] | Luchu Development Corporation [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the development of real estate properties  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 19.00% 19.00%
ASE Test Inc [Member] | TLJ Intertech Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in information software services  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 60.00% 60.00%
ASE Test Inc [Member] | MingFeng Information Service Corp., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in information software services  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 100.00% 100.00%
ASE Test Inc [Member] | Advanced Microelectronic Products Inc. ("AMPI") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the manufacturing of integrated circuit  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 43.40% 43.40%
ASE Test Inc [Member] | Alto Enterprises Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location British Virgin Islands  
Percentage of Ownership (%) 100.00% 100.00%
ASE Test Inc [Member] | Super Zone Holdings Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Hong Kong  
Percentage of Ownership (%) 100.00% 100.00%
ASE Holding Limited [Member] | ASE Test Limited ("ASE Test") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Singapore  
Percentage of Ownership (%) 10.20% 10.20%
ASE Holding Limited [Member] | ASE Investment (Labuan) Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Malaysia  
Percentage of Ownership (%) 70.10% 70.10%
J&R Holding Limited [Member] | Omniquest Industrial Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location British Virgin Islands  
Percentage of Ownership (%) 8.40% 8.40%
J&R Holding Limited [Member] | ASE Test Limited ("ASE Test") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Singapore  
Percentage of Ownership (%) 89.80% 89.80%
J&R Holding Limited [Member] | J&R Industrial Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in leasing equipment and investing activity  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 100.00% 100.00%
J&R Holding Limited [Member] | ASE Japan Co., Ltd. ("ASE Japan") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Japan  
Percentage of Ownership (%) 100.00% 100.00%
J&R Holding Limited [Member] | ASE (U.S.) Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business After-sales service and sales support  
Establishment and Operating Location U.S.A.  
Percentage of Ownership (%) 100.00% 100.00%
J&R Holding Limited [Member] | Global Advanced Packaging Technology Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location British Cayman Islands  
Percentage of Ownership (%) 100.00% 100.00%
J&R Holding Limited [Member] | Suzhou ASEN Semiconductors Co., Ltd. ("ASEN") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Suzhou, China  
Percentage of Ownership (%) 100.00% 100.00%
J&R Holding Limited [Member] | Anstock Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in financing activity  
Establishment and Operating Location British Cayman Islands  
Percentage of Ownership (%) 100.00% 100.00%
J&R Holding Limited [Member] | Anstock II Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in financing activity  
Establishment and Operating Location British Cayman Islands  
Percentage of Ownership (%) 100.00% 100.00%
Innosource Limited Investor [Member] | Omniquest Industrial Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location British Virgin Islands  
Percentage of Ownership (%) 20.60% 20.60%
Innosource Limited Investor [Member] | ASE (Shanghai) Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the production of substrates  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 8.50% 8.50%
Omniquest Industrial Limited [Member] | ASE Corporation [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location British Cayman Islands  
Percentage of Ownership (%) 100.00% 100.00%
Alto Enterprises Limited [Member] | ASE (Kunshan) Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Kun Shan, China  
Percentage of Ownership (%) 22.90% 22.90%
Alto Enterprises Limited [Member] | ASE Investment (Kun Shan) Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Kun Shan, China  
Percentage of Ownership (%) 85.90% 85.90%
Super Zone Holdings Limited [Member] | Advanced Semiconductor Engineering (China) Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 100.00%
ASE Investment Labuan Inc [Member] | ASE (Korea) Inc. ("ASE Korea") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Korea  
Percentage of Ownership (%) 100.00% 100.00%
ASE Korea [Member] | ASE WeiHai Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Shandong, China  
Percentage of Ownership (%) 100.00% 100.00%
ASE Test [Member] | ASE Test Holdings, Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location British Cayman Islands  
Percentage of Ownership (%) 100.00% 100.00%
ASE Test [Member] | ASE Holdings (Singapore) Pte. Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Singapore  
Percentage of Ownership (%) 100.00% 100.00%
ASE Test [Member] | ASE Singapore Pte. Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Singapore  
Percentage of Ownership (%) 100.00% 100.00%
ASE Test [Member] | ASE Investment (Labuan) Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Malaysia  
Percentage of Ownership (%) 29.90% 29.90%
ASE Test Holdings Ltd [Member] | ISE Labs, Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the testing of semiconductors  
Establishment and Operating Location U.S.A.  
Percentage of Ownership (%) 100.00% 100.00%
ISE Labs Inc [Member] | ISE Services Inc [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in wafer procurement and customer product management services and commenced operations in February 2020  
Establishment and Operating Location U.S.A.  
Percentage of Ownership (%) 100.00% 0.00%
ASE Holdings (Singapore) Pte Ltd [Member] | ASE Electronics (M) Sdn. Bhd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Malaysia  
Percentage of Ownership (%) 100.00% 100.00%
Global Advanced Packaging Technology Limited [Member] | ASE Assembly & Test (Shanghai) Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 100.00%
Global Advanced Packaging Technology Limited [Member] | ASE Advanced Semiconductor Shanghai Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors and was established and spun off from ASESH in November 2020  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 0.00%
ASESH [Member] | ASE Investment (Kun Shan) Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Kun Shan, China  
Percentage of Ownership (%) 14.10% 14.10%
ASESH [Member] | Shanghai Ding Hui Real Estate Development Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the development, construction and sale of real estate properties  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 60.00% 60.00%
ASESH [Member] | ISE Labs, China, Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the testing of semiconductor  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 100.00%
ASESH [Member] | Wuxi Tongzhi Microelectronics Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Wuxi, China  
Percentage of Ownership (%) 100.00% 100.00%
DH [Member] | Shanghai Ding Qi Property Management Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the management of real estate properties  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 100.00%
DH [Member] | Shanghai Ding Wei Real Estate Development Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the development, construction and leasing of real estate properties  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 100.00%
DH [Member] | Shanghai Ding Yu Real Estate Development Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the development, construction and leasing of real estate properties  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 100.00%
DH [Member] | Kun Shan Ding Hong Real Estate Development Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the development, construction and leasing of real estate properties  
Establishment and Operating Location Kun Shan, China  
Percentage of Ownership (%) 100.00% 100.00%
DH [Member] | Shanghai Ding Xu Property Management Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the management of real estate properties  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 100.00%
DH [Member] | Shanghai Dingyao Estate Development Co Ltd [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in property management and was invested in April 2020  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 0.00%
DH [Member] | Shanghai Ding Fan Business Management Co Ltd [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the management of real estate properties (acquired from DW in November 2020)  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 0.00%
DW [Member] | Shanghai Ding Fan Business Management Co Ltd [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in leasing and management of real estate properties (disposed to DH in November 2020)  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 0.00% 100.00%
ASE Investment Kun Shan Limited [Member] | ASE (Kunshan) Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Kun Shan, China  
Percentage of Ownership (%) 49.30% 49.30%
ASE Corporation [Member] | ASE Mauritius Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Mauritius  
Percentage of Ownership (%) 100.00% 100.00%
ASE Corporation [Member] | ASE Labuan Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Malaysia  
Percentage of Ownership (%) 100.00% 100.00%
ASE Mauritius Inc [Member] | ASE (Kunshan) Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Kun Shan, China  
Percentage of Ownership (%) 27.80% 27.80%
ASE Mauritius Inc [Member] | ASE (Shanghai) Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the production of substrates  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 91.50% 91.50%
ASE Labuan Inc [Member] | ASE Electronics Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the production of substrates  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 100.00% 100.00%
ASE (Shanghai) Inc. [Member] | Shanghai Ding Hui Real Estate Development Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the development, construction and sale of real estate properties  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 40.00% 40.00%
ASE (Shanghai) Inc. [Member] | Advanced Semiconductor Engineering (HK) Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the trading of substrates  
Establishment and Operating Location Hong Kong  
Percentage of Ownership (%) 100.00% 100.00%
ASE (Shanghai) Inc. [Member] | Universal Scientific Industrial (Shanghai) Co., Ltd. ("USISH") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the designing, manufacturing and sales of electronic components  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 0.80% 0.80%
USIINC [Member] | Huntington Holdings International Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location British Virgin Islands  
Percentage of Ownership (%) 100.00% 100.00%
Huntington Holdings International Co Ltd [Member] | Unitech Holdings International Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location British Virgin Islands  
Percentage of Ownership (%) 100.00% 100.00%
Huntington Holdings International Co Ltd [Member] | Real Tech Holdings Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location British Virgin Islands  
Percentage of Ownership (%) 100.00% 100.00%
Huntington Holdings International Co Ltd [Member] | Universal ABIT Holding Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business In the process of liquidation  
Establishment and Operating Location British Cayman Islands  
Percentage of Ownership (%) 100.00% 100.00%
Real Tech Holdings Limited [Member] | Universal Scientific Industrial (Kunshan) Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Liquidated in June 2020  
Establishment and Operating Location Kun Shan, China  
Percentage of Ownership (%) 0.00% 100.00%
Real Tech Holdings Limited [Member] | USI Enterprise Limited ("USIE") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the service of investment advisory and warehousing management  
Establishment and Operating Location Hong Kong  
Percentage of Ownership (%) 95.90% 95.80%
USIE [Member] | USISH [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the designing, manufacturing and sales of electronic components  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 76.60% 77.70%
USISH [Member] | Universal Global Technology Co., Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Hong Kong  
Percentage of Ownership (%) 100.00% 100.00%
USISH [Member] | Universal Global Technology (Kunshan) Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the designing and manufacturing of electronic components  
Establishment and Operating Location Kun Shan, China  
Percentage of Ownership (%) 100.00% 100.00%
USISH [Member] | Universal Global Technology (Shanghai) Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the processing and sales of computer and communication peripherals as well as business in import and export of goods and technology  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 100.00%
USISH [Member] | USI Electronics (Shenzhen) Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design, manufacturing and sales of motherboards and computer peripherals  
Establishment and Operating Location Shenzhen, China  
Percentage of Ownership (%) 50.00% 50.00%
USISH [Member] | Universal Global Electronics (Shanghai) Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the sales of electronic components and telecommunications equipment  
Establishment and Operating Location Shanghai, China  
Percentage of Ownership (%) 100.00% 100.00%
USISH [Member] | Huanrong Electronics (Huizhou) Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the research and manufacturing of new electronic applications, communications, computers and other electronics products and also provided auxiliary technical services as well as import and export services (acquired from Universal Global Electronics (Shanghai) Co., Ltd. in November 2020)  
Establishment and Operating Location Huizhou, China  
Percentage of Ownership (%) 100.00% 0.00%
USISH [Member] | FINANCIERE AFG（FAFG ) [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location France  
Percentage of Ownership (%) 10.40% 0.00%
Universal Global Technology Co Limited [Member] | USI America Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the manufacturing and processing of motherboards and wireless network communication and provision of related technical service  
Establishment and Operating Location U.S.A.  
Percentage of Ownership (%) 100.00% 100.00%
Universal Global Technology Co Limited [Member] | Universal Global Industrial Co., Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in manufacturing, trading and investing activity  
Establishment and Operating Location Hong Kong  
Percentage of Ownership (%) 100.00% 100.00%
Universal Global Technology Co Limited [Member] | Universal Global Scientific Industrial Co., Ltd. ("UGTW") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the manufacturing of components of telecomm and cars and provision of related R&D services  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 100.00% 100.00%
Universal Global Technology Co Limited [Member] | Universal Scientific Industrial De Mexico S.A. De C.V. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the assembling of motherboards and computer components  
Establishment and Operating Location Mexico  
Percentage of Ownership (%) 100.00% 100.00%
Universal Global Technology Co Limited [Member] | USI Japan Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the manufacturing and sales of computer peripherals, integrated chip and other related accessories  
Establishment and Operating Location Japan  
Percentage of Ownership (%) 100.00% 100.00%
Universal Global Technology Co Limited [Member] | USI Electronics (Shenzhen) Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design, manufacturing and sales of motherboards and computer peripherals  
Establishment and Operating Location Shenzhen, China  
Percentage of Ownership (%) 50.00% 50.00%
Universal Global Technology Co Limited [Member] | Universal Global Electronics Co., Ltd [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in accepting and outsourcing orders as well as sales of electronic components and service of technical advisory  
Establishment and Operating Location Hong Kong  
Percentage of Ownership (%) 100.00% 100.00%
Universal Global Technology Co Limited [Member] | Universal Scientific Industrial (France) ("USIFR") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in investing activities and was established in August 2019  
Establishment and Operating Location France  
Percentage of Ownership (%) 100.00% 100.00%
Universal Global Technology Co Limited [Member] | Universal Scientific Industrial Vietnam Company Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in IC assembly for wearable devices and was established in July 2020.  
Establishment and Operating Location Vietnam  
Percentage of Ownership (%) 100.00% 0.00%
UGTW [Member] | Universal Scientific Industrial Co., Ltd. ("USI") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the manufacturing, processing and sales of computers, computer peripherals and related accessories  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 100.00% 100.00%
USI Electronics Shenzhen Co Ltd [Member] | Huanrong Electronics (Huizhou) Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the research and manufacturing of new electronic applications, communications, computers and other electronics products and also provided auxiliary technical services as well as import and export services (disposed to USISH in November 2020)  
Establishment and Operating Location Huizhou, China  
Percentage of Ownership (%) 0.00% 100.00%
Universal Global Electronics Co Ltd [Member] | Semicondutores Avancados do Brasil S.A. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Liquidated in December 2020  
Establishment and Operating Location Brasil  
Percentage of Ownership (%) 0.00% 75.00%
Universal Global Electronics Co Ltd [Member] | Universal Scientific Industrial Poland Sp. z o.o. ("USIPL") (The name was changed on June 2020 and the former name was Chung Hong Electronics Poland Sp. z o.o.)    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components and new electronic applications  
Establishment and Operating Location Poland  
Percentage of Ownership (%) 100.00% 60.00%
Universal Global Electronics (Shanghai) Co., Ltd. [member] | USI Science and Technology (Shenzhen) Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design of electronic components, service of technical advisory; wholesale of electronic components and communication peripherals as well as business in import and export of goods and management of properties and was established in November 2020.  
Establishment and Operating Location Shenzhen, China  
Percentage of Ownership (%) 100.00% 0.00%
USIFR [Member] | FAFG [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location France  
Percentage of Ownership (%) 89.60% 0.00%
USIFR [Member] | ASTEELFLASH GROUP [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location France  
Percentage of Ownership (%)   0.00%
FAFG [member] | ASTEELFLASH GROUP [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location France  
Percentage of Ownership (%) 100.00% 0.00%
FAFG [member] | MANUFACTURING POWER TUNISIA [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%) 0.10%  
FAFG [member] | ASTEELFLASH MEXICO S.A. de C.V. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Mexico  
Percentage of Ownership (%) 0.10%  
ASTEELFLASH GROUP [member] | MANUFACTURING POWER TUNISIA [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%) 99.90% 0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH MEXICO S.A. de C.V. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Mexico  
Percentage of Ownership (%) 99.90% 0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH (BEDFORD) LIMITED [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location United Kingdom  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH FRANCE [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location France  
Percentage of Ownership (%) 99.90% 0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH TUNISIE S.A. [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH HONG KONG LIMITED [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location Hong Kong  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH GERMANY GmbH [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Germany  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH GROUP [member] | ASTEELFLASH US HOLDING CORP [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Holding company  
Establishment and Operating Location U.S.A.  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH GROUP [member] | ASTEEL ELECTRONIQUE FOUCHANA [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%)   0.00%
ASTEELFLASH GROUP [member] | AFERH TUNISIE [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the management, training and consulting of human resources  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%) 0.50% 0.00%
ASTEELFLASH GROUP [member] | ASTEEL ELECTRONICS MANUFACTURING SERVICES [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%) 0.10%  
ASTEELFLASH (BEDFORD) LIMITED [Member] | ASTEELFLASH TUNISIE S.A. [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%)   0.00%
ASTEELFLASH TECHNOLOGIE [Member] | ASTEELFLASH FRANCE [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location France  
Percentage of Ownership (%)   0.00%
ASTEELFLASH FRANCE [Member] | ASTEELFLASH TUNISIE S.A. [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%)   0.00%
ASTEELFLASH FRANCE [Member] | ASTEEL ELECTRONIQUE FOUCHANA [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%) 94.20% 0.00%
ASTEELFLASH FRANCE [Member] | ASTEEL ELECTRONICS MANUFACTURING SERVICES [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%) 99.90% 0.00%
ASTEELFLASH FRANCE [Member] | SCI CHASSET [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the management and operation of real estate properties and holding the ownership of real estate properties  
Establishment and Operating Location France  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH FRANCE [Member] | AFERH [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the management, training and consulting of human resources  
Establishment and Operating Location France  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH FRANCE [Member] | ASTEELFLASH TECHNOLOGIE [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in projection of plastic and the design and manufacturing of industrial components  
Establishment and Operating Location France  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH FRANCE [Member] | ASTEELFLASH BRETAGNE [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location France  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH TUNISIE S.A. [member] | ASTEEL ELECTRONIQUE TUNISIE [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH TUNISIE S.A. [member] | ASTEEL ELECTRONIQUE FOUCHANA [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%)   0.00%
AFERH [Member] | AFERH TUNISIE [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the management, training and consulting of human resources  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%) 99.50% 0.00%
ASTEELFLASH HONG KONG LIMITED [Member] | ASTEELFLASH SUZHOU CO LTD [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Suzhou, China  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH SUZHOU CO., LTD. [member] | ASTEELFLASH TUNISIE S.A. [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%)   0.00%
ASTEELFLASH SUZHOU CO., LTD. [member] | ASTEEL ELECTRONIQUE FOUCHANA [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%)   0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH TUNISIE S.A. [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%)   0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH HERSFELD GmbH [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Germany  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH EBERBACH GmbH [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Germany  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH BONN GmbH [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Germany  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH SCHWANDORF GmbH [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Germany  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH PLZEN S.R.O. [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Czech Republic  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH GERMANY GmbH [member] | ASTEELFLASH DESIGN SOLUTIONS HAMBOURG GmbH [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Germany  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH GERMANY GmbH [member] | EN ELECTRONICNETWORK SRL [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Romania  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH MEXICO S.A. de C.V. [member] | ASTEELFLASH TUNISIE S.A. [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%)   0.00%
ASTEELFLASH US HOLDING CORP. [member] | ASTEELFLASH USA CORP [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location U.S.A.  
Percentage of Ownership (%) 100.00% 0.00%
ASTEELFLASH USA CORP. [member] | ASTEELFLASH TUNISIE S.A. [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%)   0.00%
ASTEELFLASH USA CORP. [member] | ASTEEL ELECTRONIQUE FOUCHANA [Member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the design and manufacturing of electronic components  
Establishment and Operating Location Tunisia  
Percentage of Ownership (%)   0.00%
SPIL [Member] | SPIL (B.V.I.) Holding Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in investing activities  
Establishment and Operating Location British Virgin Islands  
Percentage of Ownership (%) 100.00% 100.00%
SPIL [Member] | Siliconware Investment Co., Ltd. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in investing activities  
Establishment and Operating Location R.O.C.  
Percentage of Ownership (%) 100.00% 100.00%
SPIL (B.V.I.) Holding Limited [Member] | Siliconware USA, Inc. [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in marketing activities  
Establishment and Operating Location U.S.A.  
Percentage of Ownership (%) 100.00% 100.00%
SPIL (B.V.I.) Holding Limited [Member] | SPIL (Cayman) Holding Limited [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in investing activities  
Establishment and Operating Location British Cayman Islands  
Percentage of Ownership (%) 100.00% 100.00%
SPIL Cayman Holding Limited [Member] | Siliconware Technology (Suzhou) Limited ("SZ") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors  
Establishment and Operating Location Suzhou, China  
Percentage of Ownership (%) 100.00% 100.00%
SPIL Cayman Holding Limited [Member] | Siliconware Electronics (Fujian) Co., Limited ("SF") [member]    
Disclosure of subsidiaries [Line Items]    
Main Business Engaged in the packaging and testing of semiconductors and was disposed in October 2020 (Note 30)  
Establishment and Operating Location Fujian, China  
Percentage of Ownership (%) 0.00% 100.00%