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Summary of Significant Accounting Policies - Additional Information (Detail) - EUR (€)
€ in Thousands
Mar. 31, 2019
Jan. 01, 2019
Dec. 31, 2018
Disclosure of summary of significant accounting policies [abstract]      
Lease liabilities € 17,484 € 17,700  
Operating lease commitments     € 19,627
Right-of-use assets € 17,500 € 18,400