Prepayments and other assets - Schedule of Prepayments (Detail) - EUR (€) € in Thousands  | 
Jun. 30, 2022  | 
Dec. 31, 2021  | 
Dec. 31, 2020  | 
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| Schedule of Prepayments [Abstract] | |||
| Current prepayments and other assets | € 28,694 | € 11,432 | € 8,114 | 
| Total | € 11,432 | € 8,114 | 
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- Definition Schedule of Prepayments. No definition available. 
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- Definition The amount of current prepayments and other current assets. [Refer: Other current assets; Current prepayments] Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition Receivables that represent amounts paid for goods and services before they have been delivered. Reference 1: http://www.xbrl.org/2003/role/exampleRef 
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