XML 201 R182.htm IDEA: XBRL DOCUMENT v3.21.1

Share-based Payment Arrangements - Summary of USISH's outstanding share options balance sheet (Detail) - USISH Option Plans [member] - ¥ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share options [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Range of Exercise Price Per Share	¥ 15.5	¥ 15.5
Weighted average remaining contractual life of outstanding share options	4 years 10 months 24 days	5 years 10 months 24 days
Stock option plans [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Range of Exercise Price Per Share	¥ 13.3	¥ 13.3
Weighted average remaining contractual life of outstanding share options	3 years 10 months 24 days	4 years 10 months 24 days
2020 Share Options [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Range of Exercise Price Per Share	¥ 21.7
Weighted average remaining contractual life of outstanding share options	3 years 10 months 24 days

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_DisclosureOfRangeOfExercisePricesOfOutstandingShareOptionsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The exercise price of outstanding share options.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2020-01-01
-Paragraph 45
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_45_d&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_ExercisePriceOfOutstandingShareOptions2019
Namespace Prefix:	ifrs-full_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The weighted average remaining contractual life of outstanding share options. [Refer: Weighted average [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2020-01-01
-Paragraph 45
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_45_d&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_WeightedAverageRemainingContractualLifeOfOutstandingShareOptions2019
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	ifrs-full_TypesOfSharebasedPaymentArrangementsAxis=asx_USISHOptionPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	asx_PlanNameAxis=asx_ShareOptionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	asx_PlanNameAxis=asx_StockOptionPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	asx_PlanNameAxis=asx_TwoThousandAndTwentyShareOptionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: