The exercise price of other equity instruments granted.

No definition available.

Name:	glpg_ExercisePriceOtherEquityInstrumentsGranted
Namespace Prefix:	glpg_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The expected volatility of the share price used to calculate the fair value of the other equity instruments granted.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

The option life of other equity instruments granted.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

The implied yield currently available on zero-coupon government issues of the country in whose currency the exercise price for other equity instruments granted is expressed, with a remaining term equal to the expected term of the instruments being valued.

+ References

No definition available.

+ Details

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Namespace Prefix:	glpg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The share price of other equity instruments granted at acceptance date.

+ References

No definition available.

+ Details

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Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- 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

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of expense arising from share-based payment transactions in which the goods or services received did not qualify for recognition as assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 51
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_51_a&doctype=Standard
-URIDate 2017-03-09

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The weighted average fair value at the measurement date of granted equity instruments other than share options. [Refer: Weighted average [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2017-01-01
-Paragraph 47
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2017-03-01&anchor=para_47_b&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Warrant Plans - Valuation (Details) - EUR (€)	12 Months Ended
Warrant Plans - Valuation (Details) - EUR (€)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Warrant Plans
Warrants expense	€ 16,536,000	€ 11,034,000	€ 5,036,000
2017 allocated on May 2017
Warrant Plans
Exercise Price	€ 80.57
Share price at acceptance date	€ 68.67
Fair value on the acceptance date	€ 26.85
Estimated volatility (%)	40.06%
Time to expiration (years)	8 years
Risk free rate (%)	0.33%
2017 RMV allocated on May 2017
Warrant Plans
Exercise Price	€ 80.57
Share price at acceptance date	€ 68.67
Fair value on the acceptance date	€ 26.80
Estimated volatility (%)	40.08%
Time to expiration (years)	8 years
Risk free rate (%)	0.29%
2016 (B) allocated on January 2017
Warrant Plans
Exercise Price	€ 62.50
Share price at acceptance date	€ 75.18
Fair value on the acceptance date	€ 37.27
Estimated volatility (%)	40.33%
Time to expiration (years)	8 years
Risk free rate (%)	0.51%
2016 allocated on June 2016
Warrant Plans
Exercise Price	€ 46.10
Share price at acceptance date	€ 48.71
Fair value on the acceptance date	€ 21.95
Estimated volatility (%)	40.69%
Time to expiration (years)	8 years
2016 RMV allocated on June 2016
Warrant Plans
Exercise Price	€ 46.10
Share price at acceptance date	€ 47.63
Fair value on the acceptance date	€ 21.16
Estimated volatility (%)	40.69%
Time to expiration (years)	8 years
2015 (B) allocated on December 2015
Warrant Plans
Exercise Price	€ 49.00
Share price at acceptance date	€ 39.85
Fair value on the acceptance date	€ 15.41
Estimated volatility (%)	41.10%
Time to expiration (years)	8 years
Risk free rate (%)	0.24%
2015 RMV allocated on December 2015
Warrant Plans
Exercise Price	€ 49.00
Share price at acceptance date	€ 39.78
Fair value on the acceptance date	€ 15.39
Estimated volatility (%)	41.08%
Time to expiration (years)	8 years
Risk free rate (%)	0.28%
2015 allocated on April 2015
Warrant Plans
Exercise Price	€ 28.75
Share price at acceptance date	€ 46.09
Fair value on the acceptance date	€ 26.05
Estimated volatility (%)	39.20%
Time to expiration (years)	8 years
Risk free rate (%)	0.39%