Debt and equity ratio.

No definition available.

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- Definition

Exchange rate exposure.

+ References

No definition available.

+ Details

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- Definition

Fair value of unquoted shares decreased.

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Fair value of unsecured subordinated corporate bonds decreased.

+ References

No definition available.

+ Details

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- Definition

Increase (decrease) in other comprehensive income.

+ References

No definition available.

+ Details

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- Definition

Increase decrease profit loss before tax.

+ References

No definition available.

+ Details

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- Definition

Increase percentage of significant unobservable inputs discount rate.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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Period Type:	duration

- Definition

Percentage of trade receivables.

+ References

No definition available.

+ Details

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Namespace Prefix:	asx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Significant unobservable inputs discount rate.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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Period Type:	duration

- 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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Data Type:	xbrli:stringItemType
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Period Type:	duration

- 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

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Data Type:	xbrli:monetaryItemType
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- Details

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- Details

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- Details

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- Details

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Data Type:	na
Balance Type:
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- Details

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Data Type:	na
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- Details

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Data Type:	na
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- Details

Name:	ifrs-full_TypesOfRisksAxis=ifrs-full_CurrencyRiskMember
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- Details

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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