Subsequent Event (Details) - 1 months ended Jul. 31, 2019 - Subsequent Event [Member] $ in Millions	USD ($)	EUR (€)
Galapagos Collaboration Agreement [Member]
Subsequent Event [Line Items]
Up-front license and option fee payment upon closing of collaboration agreement	$ 3,950
Estimated equity investment upon closing of the subscription agreement	1,100
Potential Milestone Payment Upon Marketing Approval of GLPG-1972	325
Potential Option Exercise Fee for GLPG-1972	250
Potential Milestone for GLPG-1972 after Option Exercise	750
Potential Option Exercise Fee Per Program	$ 150
Galapagos Collaboration Agreement [Member] | Minimum [Member]
Subsequent Event [Line Items]
Potential Sales Based Tiered Royalties	20.00%	20.00%
Galapagos Collaboration Agreement [Member] | Maximum [Member]
Subsequent Event [Line Items]
Potential Sales Based Tiered Royalties	24.00%	24.00%
Galapagos Subscription Agreement [Member]
Subsequent Event [Line Items]
Potential Ownership Percentage in Galapagos Upon Closing of the Subscription Agreement	20.10%	20.10%
Potential Subscription Price | €		€ 140.59
Potential Ownership Percentage in Galapagos Upon Warrant Exercises	29.90%	29.90%
Standstill Restricting Term	10 years	10 years
Maximum Ownership Percentage in Galapagos Based on the Terms of the Subscription Agreement	29.90%	29.90%
Minimum Ownership Percentage in Galapagos Based on the Terms of the Subscription Agreement	20.10%	20.10%