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Customer Accounts Receivable and Other Current Assets - Additional Information (Detail) - EUR (€)
€ in Thousands
12 Months Ended
Jul. 04, 2016
Dec. 31, 2017
Dec. 31, 2015
Trade and other receivables [abstract]      
Trade receivables payment terms   Less than one year  
Research tax credit current adjustment € 900 € 113 € (18)