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Related Parties and Information about Significant Non-Recurring Events and A tipycal/Unusual Transactions - Additional Information (Detail) - EUR (€)
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Disclosure Of Transactions Between Related Parties [Line Items]      
Loans and/or guarantees provided to key management personnel € 0    
Payment received from parents majority shareholder 2,500,000    
Legal Services | Parent [member]      
Disclosure Of Transactions Between Related Parties [Line Items]      
Cost € 392,000 € 32,000  
Consultancy Fees For Business Strategy | Parent [member]      
Disclosure Of Transactions Between Related Parties [Line Items]      
Cost   € 133,000 € 286,000