| Calculation standard | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | IFRS | |
| Years | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004 |
| Subscribed capital, EUR million | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 83.0 | 71.0 |
| Earnings per share (euros) (EPS)* | 2.36 | 2.35 | 2.37 | 2.34 | 2.19 | 2,05 | 1,90 | 1,98 | 2,11 | 1,61 | 1,52 | 1,41 | 1,25 | 1,33 | 1,29 | 0,96 | 1,13 | 1,12 | 1,38 | 0,97 | 1,22 | 1,10 |
| Shareholders' equity/share (euros) | 7.80 | 8,05 | 8,05 | 7,78 | 7,48 | 7,39 | 7,19 | 7,06 | 6,52 | 6,08 | 5,80 | 5,51 | 5,41 | 5,37 | 5,36 | 5,33 | 5,78 | 5,61 | 6,53 | 8,07 | 8,06 | 6,23 |
| Dividend per share, EUR** | 2.40 | 2,35 | 2,25 | 2,15 | 2,05 | 1,95 | 1,85 | 1,75 | 1,65 | 1,50 | 1,40 | 1,32 | 1,30 | 1,30 | 1,30 | 1,30 | 1,42 | 1,00 | 1,80 | 1,50 | 0.70 | 0.80 |
| Effective dividend yield, %*** | 6.4 % | 5.6 % | 5.4 % | 4.3 % | 3.8 % | 4.3 % | 3.8 % | 4.9 % | 5.0 % | 4.8 % | 4.0 % | 5.8 % | 6.7 % | 7.8 % | 8.1 % | 8.0 % | 8.9 % | 8.1 % | 8.6 % | 7.2 % | 4.5 % | 6.7 % |
| Price/Earnings Ratio (P/E) | 16.0 | 17.8 | 17.7 | 21.1 | 24.7 | 21.9 | 25.9 | 18.2 | 15.5 | 19.2 | 22.9 | 16.0 | 15.4 | 12.6 | 12.5 | 16.9 | 14.1 | 11.0 | 15.2 | 21.4 | 12.8 | 10.8 |
| Share price at year‑end, EUR | 37.74 | 41.80 | 41,87 | 49,46 | 54,12 | 44,87 | 49,25 | 36,08 | 32,72 | 30,97 | 34,79 | 22,61 | 19,26 | 16,73 | 16,13 | 16,27 | 15,96 | 12,30 | 21,00 | 20,75 | 15,65 | 11,86 |
| Middle price, EUR | 43.11 | 43,23 | 48,86 | 51,99 | 51,00 | 51,09 | 42,28 | 36,33 | 33,74 | 32,27 | 28,37 | 20,93 | 16,15 | 16,61 | 15,41 | 15,39 | 12,01 | 15,02 | 21,31 | 17,06 | 13,95 | 11,36 |
| Lowest price, EUR | 48.16 | 40,18 | 39,41 | 45,57 | 45,10 | 42,13 | 35,91 | 31,90 | 30,42 | 28,40 | 22,10 | 18,19 | 13,37 | 14,84 | 12,70 | 12,67 | 9,69 | 9,85 | 18,63 | 14,00 | 10,56 | 8,80 |
| Highest price, EUR | 36.46 | 49,08 | 56,52 | 56,90 | 56,18 | 58,64 | 49,63 | 41,85 | 36,94 | 35,80 | 35,99 | 24,04 | 19,49 | 17,97 | 17,00 | 17,43 | 15,99 | 22,18 | 24,41 | 20,76 | 16,79 | 14,50 |
| Market capitalisation, EUR million | 6315 | 6995 | 7006 | 8276 | 9056 | 7508 | 8241 | 6037 | 5475 | 5176 | 5822 | 3603 | 3069 | 2625 | 2520 | 2534 | 2484 | 1914 | 3323 | 3360 | 2596 | 1682 |
* Comparable
** Board of Directors proposal
*** Effective dividend yield: Dividend per share / Closing price of the financial year