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Property and equipment - Additional Information (Detail) - EUR (€)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Disclosure of detailed information about property, plant and equipment [abstract]    
Impairment charge on leasehold improvements € 0 € 6,000,000
Leasehold improvements not placed into service € 59,000,000 € 15,000,000