XML 55 R204.htm IDEA: XBRL DOCUMENT
v3.20.1

Financial Instruments - Additional Information (Detail) $ in Thousands, $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 TWD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 TWD ($) | Dec. 31, 2017 TWD ($) | Dec. 31, 2019 USD ($)
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |
Significant unobservable inputs discount rate | 31.00% | 31.00% |  |  |
Increase percentage of significant unobservable inputs discount rate | 1.00% | 1.00% | 0.10% |  |
Fair value of unquoted shares decreased | $ 7,200 |  | $ 7,700 |  | $ 241
Fair value of bonds decreased | $ 6,000 | $ 201 | $ 7,000 |  |
Percentage of trade receivables | 37.00% |  | 36.00% |  | 37.00%
Call options [member] |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |
Significant unobservable inputs discount rate | 20.00% | 20.00% |  |  |
At fair value [member] | Call options [member] |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |
Increase percentage of significant unobservable inputs discount rate | 0.10% | 0.10% |  |  |
Fair value of bonds decreased | $ 855 | $ 29 |  |  |
Bottom of range [member] | Actuarial assumption of discount rates [member] |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |
Significant unobservable inputs discount rate | 20.00% | 20.00% |  |  |
Top of range [member] | Actuarial assumption of discount rates [member] |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |
Significant unobservable inputs discount rate | 30.00% | 30.00% |  |  |
Floating interest rate [member] |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |
Increase decrease in profit before tax | $ 1,232,000 | $ 41,190 | $ 1,398,000 | $ 24,000 |
Currency risk [member] |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |
Value at risk | $ 82,000 |  | 129,000 | 101,000 | $ 2,742
Exchange rate exposure | 100.00% | 100.00% |  |  |
Other price risk [member] |  |  |  |  |
Disclosure of detailed information about financial instruments [line items] |  |  |  |  |
Increase decrease in profit before tax | $ 51,000 | $ 1,705 | $ 64,000 | 52,000 |
Equity debt ratio |  |  | 1.00% |  |
Increase decrease in other comprehensive income | $ 8,000 | $ 267 | $ 16,000 | $ 13,000 |

X
- Definition Debt and equity ratio. + References No definition available. + Details
Name: | asx_DebtAndEquityRatio
Namespace Prefix: | asx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Exchange rate exposure. + References No definition available. + Details
Name: | asx_ExchangeRateExposure
Namespace Prefix: | asx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of unquoted shares decreased. + References No definition available. + Details
Name: | asx_FairValueOfUnquotedSharesDecreased
Namespace Prefix: | asx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of unsecured subordinated corporate bonds decreased. + References No definition available. + Details
Name: | asx_FairValueOfUnsecuredSubordinatedCorporateBondsDecreased
Namespace Prefix: | asx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Increase (decrease) in other comprehensive income. + References No definition available. + Details
Name: | asx_IncreaseDecreaseInOtherComprehensiveIncome
Namespace Prefix: | asx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Increase decrease profit loss before tax. + References No definition available. + Details
Name: | asx_IncreaseDecreaseProfitLossBeforeTax
Namespace Prefix: | asx_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Increase percentage of significant unobservable inputs discount rate. + References No definition available. + Details
Name: | asx_IncreasePercentageOfSignificantUnobservableInputsDiscountRate
Namespace Prefix: | asx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of trade receivables. + References No definition available. + Details
Name: | asx_PercentageOfTradeReceivables
Namespace Prefix: | asx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Significant unobservable inputs discount rate. + References No definition available. + Details
Name: | asx_SignificantUnobservableInputsDiscountRate
Namespace Prefix: | asx_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- 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
Name: | ifrs-full_DisclosureOfFinancialInstrumentsLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The measure of a potential loss exposure as a result of future market movements, based on a specified confidence interval and measurement horizon. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IFRS -Number 7 -IssueDate 2019-01-01 -Paragraph 41 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2019-en-r&anchor=para_41&doctype=Standard -URIDate 2019-03-27 + Details
Name: | ifrs-full_ValueAtRisk
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | ifrs-full_ClassesOfFinancialInstrumentsAxis=ifrs-full_PurchasedCallOptionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_MeasurementAxis=ifrs-full_AtFairValueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_ActuarialAssumptionsAxis=ifrs-full_ActuarialAssumptionOfDiscountRatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfInterestRatesAxis=ifrs-full_FloatingInterestRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfRisksAxis=ifrs-full_CurrencyRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ifrs-full_TypesOfRisksAxis=ifrs-full_OtherPriceRiskMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |