Research and development expenses (Details) - EUR (€) € in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Research and development expenses
Personnel expenses	€ 45,733	€ 26,519	€ 16,473
External research and development expenses	137,050	48,859	27,893
Materials and consumables	2,027	1,464	1,562
Depreciation and amortisation	1,641	494	446
Other expenses	11,214	6,273	5,366
Research and development expenses	€ 197,665	€ 83,609	€ 51,740

Represents depreciation and amortisation of assets used in research and development.

No definition available.

Name:	argx_DepreciationAndAmortisationExpenseResearchAndDevelopment
Namespace Prefix:	argx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

N/A

+ References

No definition available.

+ Details

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Namespace Prefix:	argx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The expense of all forms of consideration given by an entity in exchange for a service rendered by employees or for the termination of employment classified as research and development expenses.

+ References

No definition available.

+ Details

Name:	argx_EmployeeBenefitExpensesClassifiedAsResearchAndDevelopmentExpenses
Namespace Prefix:	argx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of expenditure directly attributable to external research or development activities, recognised in profit or loss.

+ References

No definition available.

+ Details

Name:	argx_ExternalResearchAndDevelopmentExpenses
Namespace Prefix:	argx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents expenses incurred in research and development not separately disclosed.

+ References

No definition available.

+ Details

Name:	argx_OtherResearchAndDevelopmentExpenses
Namespace Prefix:	argx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents raw materials and consumables expenses incurred in the R&D process.

+ References

No definition available.

+ Details

Name:	argx_RawMaterialsAndConsumablesUsedInResearchAndDevelopment
Namespace Prefix:	argx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of expenditure directly attributable to research or development activities, recognised in profit or loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 38
-IssueDate 2019-01-01
-Paragraph 126
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=38&code=ifrs-tx-2019-en-r&anchor=para_126&doctype=Standard
-URIDate 2019-03-27

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration