| Key figures in a multi-year comparison |  | 2024 |  | 2023 |  | 2022 |  | 2021 |  | 2020 |  | 
|  |  | Konzern IFRS |  | Konzern IFRS |  | Konzern IFRS |  | Konzern IFRS |  | Konzern IFRS |  | 
| Yield data |  | 
| Sales revenue (in Mio. EUR) |  | 476.0 |  | 479.3 |  | 487.1 |  | 440.1 |  | 383.6 |  | 
| Sales growth (in % compared to previous year) |  | -0.7 |  | -1.6 |  | 10.7 |  | 14.7 |  | 3.0 |  | 
| Earnings before interest and taxes (EBIT) (in EUR million) |  | 42.8 |  | 34.5 |  | 36.3 |  | 47.5 |  | 40.1 |  | 
| EBIT margin (in %) |  | 9.0 |  | 7.2 |  | 7.5 |  | 10.8 |  | 10.5 |  | 
| Result after taxes (in EUR million) |  | 29.5 |  | 22.6 |  | 26.1 |  | 33.7 |  | 29.5 |  | 
| Financial data |  | 
| Investments (in EUR million) |  | 14.7 |  | 20.4 |  | 41.1 |  | 35.8 |  | 15.6 |  | 
| Depreciation and amortization (in EUR million) |  | 21.5 |  | 18.7 |  | 17.2 |  | 15.6 |  | 14.8 |  | 
| Cash flow from operating activities (in EUR million) |  | 53.1 |  | 48.7 |  | 7.2 |  | 42.4 |  | 56.0 |  | 
| Balance sheet data |  | 
| Balance sheet total (in EUR million) |  | 431.0 |  | 420.0 |  | 412.6 |  | 365.4 |  | 319.2 |  | 
| Trade receivables (in EUR million) |  | 33.4 |  | 36.6 |  | 35.1 |  | 34.3 |  | 28.6 |  | 
| Inventories (in EUR million) |  | 69.1 |  | 69.9 |  | 89.7 |  | 63.6 |  | 48.4 |  | 
| Fixed assets (incl. investment properties) (in EUR million) |  | 258.9 |  | 254.9 |  | 247.3 |  | 216.6 |  | 192.8 |  | 
| Trade payables (in EUR million) |  | 16.1 |  | 16.0 |  | 18.7 |  | 22.4 |  | 15.0 |  | 
| Non-current and current liabilities (in EUR million) |  | 150.7 |  | 162.7 |  | 168.6 |  | 141.9 |  | 127.9 |  | 
| Equity (incl. non-controlling interests) (in EUR million) |  | 280.3 |  | 257.3 |  | 244.0 |  | 223.5 |  | 191.3 |  | 
| Return on equity (in %) |  | 16.6 |  | 14.1 |  | 16.3 |  | 24.8 |  | 23.5 |  | 
| Equity ratio (in %) |  | 65.0 |  | 61.3 |  | 59.1 |  | 61.2 |  | 59.9 |  | 
| Net gearing ratio (in years) |  | 0.6 |  | 1.1 |  | 1.3 |  | 0.4 |  | 0.4 |  | 
| Employees (average) |  | 1,490 |  | 1,480 |  | 1,466 |  | 1,395 |  | 1,335 |  |