v3.20.1

Significant accounting policies - Employee Benefits (Details) | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017
Significant accounting policies |  |
Percentage of bonus paid immediately around year-end, Senior Management Bonus Scheme | 50.00% | 50.00%
Percentage of deferred bonus paid for three years, Senior Management Bonus Scheme | 50.00% | 50.00%
Term of deferrment for the remaining 50% bonus payment, Senior Management Bonus Scheme | 3 years | 3 years
Share price below threshold in which the deferred bonus will be adjusted and the remainder will be forfeited | 10.00% | 10.00%
Share price above threshold in which the deferred bonus will be forfeited | 10.00% | 10.00%

X
- Definition Term of deferment in years for the remaining 50% bonus payment under the Senior Management Bonus Scheme. + References No definition available. + Details
Name: | glpg_BounsPlanRemainderPercentageDueAmortizationPeriod
Namespace Prefix: | glpg_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The disclosure of significant accounting policies. + References No definition available. + Details
Name: | glpg_DisclosureOfSignificantAccountingPoliciesAbstract
Namespace Prefix: | glpg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the percentage of the senior management bounus scheme paid immediately around year-end. + References No definition available. + Details
Name: | glpg_PercentageOfSeniorManagementBonusSchemePaidImmediatelyAroundYearEnd
Namespace Prefix: | glpg_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Remaining percentage of bonus deferred and paid for next three years under the Senior Management Bonus Scheme. + References No definition available. + Details
Name: | glpg_RemainingPercentageOfSeniorManagementBonusSchemePaidDeferredForThreeYears
Namespace Prefix: | glpg_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share price threshold percentage in which the deferred bonus will be adjusted and the remainder will be forfeited. + References No definition available. + Details
Name: | glpg_ThresholdForDeferredBounsPaymentToBeAdjusted
Namespace Prefix: | glpg_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Share price threshold percentage in which the deferred bonus will be forfeited. + References No definition available. + Details
Name: | glpg_ThresholdForDeferredBounsPaymentToBeForfeited
Namespace Prefix: | glpg_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration