Name:	glpg_IfrsShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod
Namespace Prefix:	glpg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

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

No definition available.

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

The percentage of warrants vested.

No definition available.

Name:	glpg_PercentageOfWarrantsVested
Namespace Prefix:	glpg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

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

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2019-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2019-en-r&anchor=para_47_b&doctype=Standard
-URIDate 2019-03-27

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 2
-IssueDate 2019-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2019-en-r&anchor=para_45&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_NumberOfInstrumentsOtherEquityInstrumentsGranted
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 2
-IssueDate 2019-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2019-en-r&anchor=para_45&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_NumberOfOtherEquityInstrumentsExercisableInSharebasedPaymentArrangement
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

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

Name:	ifrs-full_NumberOfOtherEquityInstrumentsExpiredInSharebasedPaymentArrangement
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

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

Name:	ifrs-full_NumberOfOtherEquityInstrumentsForfeitedInSharebasedPaymentArrangement
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

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

Name:	ifrs-full_NumberOfOtherEquityInstrumentsOutstandingInSharebasedPaymentArrangement
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

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