v3.20.1

Share capital - History - Narrative (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share capital
Aggregate share capital	€ 349,789	€ 294,600	€ 275,510	€ 250,187
Aggregate number of shares after transaction	64,667,000	54,466,000	50,937,000	46,256,000
Number of shares	64,666,802	54,465,421	50,936,778	46,256,078

X

- Definition

The aggregate number of shares issued by the entity.

+ References

No definition available.

+ Details

Name:	glpg_AggregateNumberOfSharesAfterTransaction
Namespace Prefix:	glpg_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The amount of aggregate share capital after the transaction.

+ References

No definition available.

+ Details

Name:	glpg_AggregateShareCapitalAfterTransaction
Namespace Prefix:	glpg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- References

No definition available.

+ Details

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

X

- Definition

The number of shares issued by the entity, for which full payment has been received.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2019-01-01
-Paragraph 79
-Subparagraph a
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2019-en-r&anchor=para_79_a_ii&doctype=Standard
-URIDate 2019-03-27

+ Details

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