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v3.20.1

Lease Arrangements - Additional Information (Detail) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 TWD ($)
Disclosure of detailed information about property, plant and equipment [line items] |
Minimum Lease Payments | $ 785,295
Land [member] | Bottom of range [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Lease Term | 1 year
Land [member] | Top of range [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Lease Term | 69 years
Buildings [member] | Bottom of range [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Lease Term | 1 year
Buildings [member] | Top of range [member] |
Disclosure of detailed information about property, plant and equipment [line items] |
Lease Term | 31 years

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- Definition Lease term + References No definition available. + Details
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Namespace Prefix: | asx_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Minimum lease payments + References No definition available. + Details
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Namespace Prefix: | asx_
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Balance Type: | debit
Period Type: | duration

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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | ifrs-full_ClassesOfPropertyPlantAndEquipmentAxis=ifrs-full_BuildingsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |