Name:	glpg_IncreaseDecreaseInNetBookValueDueToReasonablyPossibleChangeInDesignatedRiskComponent
Namespace Prefix:	glpg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The reasonably possible percentage of change in the designated risk component used to determine the value of the financial instrument. Excludes defined benefit plan obligations.

No definition available.

Name:	glpg_PercentageOfReasonablyPossibleChangeInRiskAssumption
Namespace Prefix:	glpg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The reasonably possible percentage of the decrease in the designated risk component used to determine the value of the financial instrument. Excludes defined benefit plan obligations.

No definition available.

Name:	glpg_PercentageOfReasonablyPossibleDecreaseInRiskAssumption
Namespace Prefix:	glpg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The reasonably possible percentage of the increase in the designated risk component used to determine the value of the financial instrument. Excludes defined benefit plan obligations

No definition available.

Name:	glpg_PercentageOfReasonablyPossibleIncreaseInRiskAssumption
Namespace Prefix:	glpg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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.

No definition available.

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

The increase (decrease) in profit (loss) that would have been caused by a reasonably possible decrease in the risk exposure that arises from contracts within the scope of IFRS 17.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2021-01-01
-Name IFRS
-Number 17
-IssueDate 2019-01-01
-Paragraph 128
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=17&code=ifrs-tx-2019-en-r&anchor=para_128_a_i&doctype=Standard
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2021-01-01
-Name IFRS
-Number 17
-IssueDate 2019-01-01
-Paragraph 128
-Subparagraph a
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=17&code=ifrs-tx-2019-en-r&anchor=para_128_a_ii&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_IncreaseDecreaseInProfitLossDueToReasonablyPossibleDecreaseInRiskExposureThatArisesFromContractsWithinScopeOfIFRS17
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The increase (decrease) in profit (loss) that would have been caused by a reasonably possible increase in the risk exposure that arises from contracts within the scope of IFRS 17.

Name:	ifrs-full_IncreaseDecreaseInProfitLossDueToReasonablyPossibleIncreaseInRiskExposureThatArisesFromContractsWithinScopeOfIFRS17
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Name:	ifrs-full_TypesOfRisksAxis=ifrs-full_InterestRateRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

Name:	srt_CurrencyAxis=glpg_EuroUsdExchangeRateValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_CurrencyAxis=glpg_EuroGbpExchangeRateValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_CurrencyAxis=glpg_EuroChFrancsExchangeRateValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_CurrencyAxis=glpg_EuroHrKunasExchangeRateValueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: