Represents the liability (asset) of defined benefit plans included in the balance sheet.

No definition available.

Name:	glpg_LiabilityAssetOfDefinedBenefitPlansIncludedInBalanceSheet
Namespace Prefix:	glpg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The present value, without deducting any plan assets, of expected future payments required to settle the obligation resulting from employee service in the current and prior periods. [Refer: Plan assets, at fair value]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 57
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_57_a&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_DefinedBenefitObligationAtPresentValue
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

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

- Definition

The increase (decrease) in the net defined benefit liability (asset) resulting from changes that the entity does not separately disclose in the same statement or note. [Refer: Net defined benefit liability (asset)]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 141
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_141&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- Definition

The fair value of defined benefit plan assets. Plan assets comprise assets held by a long-term employee benefit fund and qualifying insurance policies. [Refer: At fair value [member]]

+ References

+ Details

Name:	ifrs-full_PlanAssetsAtFairValue
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The present value of the defined benefit obligation, less the fair value of the plan assets (if any). [Refer: Plan assets [member]]

+ References

+ Details

Name:	ifrs-full_SurplusDeficitInPlan
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	ifrs-full_NetDefinedBenefitLiabilityAssetAxis=ifrs-full_PresentValueOfDefinedBenefitObligationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_NetDefinedBenefitLiabilityAssetAxis=glpg_PresentValueOfFundedDefinedBenefitObligationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_NetDefinedBenefitLiabilityAssetAxis=glpg_PresentValueOfUnfundedDefinedBenefitObligationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Retirement benefit plans - Obligations included in the balance sheet (Details) - EUR (€) € in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Disclosure of net defined benefit liability (asset) [line items]
Plan assets	€ (1,064)	€ (2,555)	€ (1,789)
Deficit/surplus	(1,064)	169	387
Reclassification - Belgian contribution plans	1,064
Liability included in the balance sheet	2,693	3,582	3,520	€ 2,865
Present value of defined benefit obligation [member]
Disclosure of net defined benefit liability (asset) [line items]
Reclassification - Belgian contribution plans	1,064
Funded defined benefit obligation [member]
Disclosure of net defined benefit liability (asset) [line items]
Present value of defined benefit obligation		2,724	2,175
Unfunded defined benefit obligation [member]
Disclosure of net defined benefit liability (asset) [line items]
Present value of defined benefit obligation	€ 2,693	€ 3,412	€ 3,133