Name:	glpg_AdjustmentForItemsToDiscloseSeparatelyUnderOperatingCashFlow
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Balance Type:	debit
Period Type:	duration

Adjustments for non-cash items to reconcile profit (loss) to net cash flow from (used in) operating activities.

No definition available.

Name:	glpg_AdjustmentForNonCashTransactions
Namespace Prefix:	glpg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of adjustment for discounting effect of deferred income.

No definition available.

Name:	glpg_AdjustmentsForDiscountingEffectOfDeferredIncome
Namespace Prefix:	glpg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Fair value re-measurement of share subscription agreement and warrants.

No definition available.

Name:	glpg_AdjustmentsForFairValueRemeasurementOfShareSubscriptionAgreementAndWarrants
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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

Adjustments for gain (loss) on disposals, financial assets held at fair value through profit of loss.

No definition available.

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

Adjustments for unrealized foreign exchange losses (gains) to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Profit (loss)]

No definition available.

Name:	glpg_AdjustmentsForUnrealizedForeignExchangeLossesGains
Namespace Prefix:	glpg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The increase (decrease) in working capital, excluding deferred income.

No definition available.

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

The amount of net fair value adjustment current financial investments.

No definition available.

Name:	glpg_NetFairValueAdjustmentRelatingToCurrentFinancialInvestments
Namespace Prefix:	glpg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The amount of cash inflow from interest related to current financial investments.

No definition available.

Name:	glpg_ProceedsFromInterestReceivedRelatedToCurrentFinancialInvestments
Namespace Prefix:	glpg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Adjustments for decrease (increase) in inventories to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Inventories; Profit (loss)]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2019-01-01
-Paragraph 20
-Subparagraph a
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Name:	ifrs-full_AdjustmentsForDecreaseIncreaseInInventories
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Adjustments for decrease (increase) in trade accounts receivable to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Profit (loss)]

Name:	ifrs-full_AdjustmentsForDecreaseIncreaseInTradeAccountReceivable
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Adjustments for depreciation and amortisation expense to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Depreciation and amortisation expense; Profit (loss)]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2019-01-01
-Paragraph 20
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=7&code=ifrs-tx-2019-en-r&anchor=para_20_b&doctype=Standard
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Name:	ifrs-full_AdjustmentsForDepreciationAndAmortisationExpense
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Adjustments for fair value losses (gains) to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Profit (loss)]

Name:	ifrs-full_AdjustmentsForFairValueGainsLosses
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Adjustments for impairment loss (reversal of impairment loss) recognised in profit or loss to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Impairment loss (reversal of impairment loss) recognised in profit or loss]

Name:	ifrs-full_AdjustmentsForImpairmentLossReversalOfImpairmentLossRecognisedInProfitOrLoss
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Adjustments for increase (decrease) in employee benefit liabilities to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Profit (loss)]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2019-01-01
-Paragraph 20
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=7&code=ifrs-tx-2019-en-r&anchor=para_20&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_AdjustmentsForIncreaseDecreaseInEmployeeBenefitLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Adjustments for increase (decrease) in trade accounts payable to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Profit (loss)]

Name:	ifrs-full_AdjustmentsForIncreaseDecreaseInTradeAccountPayable
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

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

Adjustments for share-based payments to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Profit (loss)]

Name:	ifrs-full_AdjustmentsForSharebasedPayments
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The cash outflow for finance costs paid, classified as operating activities. [Refer: Finance costs]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2019-01-01
-Paragraph 31
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=7&code=ifrs-tx-2019-en-r&anchor=para_31&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_FinanceCostsPaidClassifiedAsOperatingActivities
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The cash inflow from finance income received, classified as operating activities. [Refer: Finance income]

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The cash outflow for income taxes paid, classified as operating activities.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2019-01-01
-Paragraph 35
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=7&code=ifrs-tx-2019-en-r&anchor=para_35&doctype=Standard
-URIDate 2019-03-27

Name:	ifrs-full_IncomeTaxesPaidClassifiedAsOperatingActivities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Adjustments to reconcile profit (loss) to net cash flow from (used in) operating activities for which cash effects are investing or financing cash flow, that the entity does not separately disclose in the same statement or note. [Refer: Profit (loss)]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2019-01-01
-Paragraph 20
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=7&code=ifrs-tx-2019-en-r&anchor=para_20_c&doctype=Standard
-URIDate 2019-03-27