Price of a single share of the company's stock.

No definition available.

Name:	glpg_IfrsSharePrice
Namespace Prefix:	glpg_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Increase in Share Capital and issuance premium due to Issuance of Warrants

+ References

No definition available.

+ Details

Name:	glpg_IncreaseInShareCapitalAndIssuancePremiumDueToIssuanceOfWarrants
Namespace Prefix:	glpg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The number of other equity instruments (ie other than share options) exercised in a share-based payment arrangement.

+ References

No definition available.

+ Details

Name:	glpg_NumberOfOtherEquityInstrumentsExercisedInShareBasedPaymentArrangement
Namespace Prefix:	glpg_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average exercise price of other equity instruments (ie other than share options) exercised in a share-based payment arrangement. [Refer: Weighted average [member]]

+ References

No definition available.

+ Details

Name:	glpg_WeightedAverageExercisePriceOfOtherEquityInstrumentsExercisedInShareBasedPaymentArrangement
Namespace Prefix:	glpg_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
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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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of shares issued by the entity.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 106
-Subparagraph d
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_106_d&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_NumberOfSharesIssued
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	glpg_IfrsScenarioAxis=glpg_IfrsScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_NonadjustingEventsAfterReportingPeriodAxis=glpg_ExerciseOfWarrantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Events after balance sheet date (Details)		12 Months Ended
Events after balance sheet date (Details)	Mar. 20, 2018 EUR (€) EquityInstruments € / shares shares	Dec. 31, 2017 EquityInstruments	Dec. 31, 2016 EquityInstruments	Dec. 31, 2015 EquityInstruments
Disclosure of non-adjusting events after reporting period [line items]
Warrants exercised \| EquityInstruments		368,200	419,035	1,244,714
Forecast \| Exercise of Warrants [Member]
Disclosure of non-adjusting events after reporting period [line items]
Warrants exercised \| EquityInstruments	298,184
Average exercise price warrants \| €	€ 13.16
Increase to share capital and issuance premium due to warrants issued \| €	€ 3,924,200
Number of shares issued \| shares	298,184
Closing share price \| € / shares	€ 83.72