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
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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
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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