Financial risk management - Summary of Sensitivity Analysis of Fair Value Measurement to Changes in Unobservable Inputs, Liabilities (Detail) - Interest rate, measurement input [member] - Interest rate risk [member] - EUR (€) € in Thousands  | 
12 Months Ended | |||
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Dec. 31, 2021  | 
Dec. 31, 2020  | 
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| Disclosure of sensitivity analysis of fair value measurement to changes in unobservable inputs, liabilities [line items] | ||||
| Interest rates – increase by 10 basis points | [1] | € 76 | € 23 | |
| Interest rates – decrease by 10 basis points | [1] | € (68) | € (16) | |
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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table. No definition available. 
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- Definition The amount of increase (decrease) in the fair value measurement of liabilities, recognised in profit or loss after tax, due to a reasonably possible decrease in an unobservable input. [Refer: Tax income (expense)] Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition The amount of increase (decrease) in the fair value measurement of liabilities, recognised in profit or loss after tax, due to a reasonably possible increase in an unobservable input. [Refer: Tax income (expense)] Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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