| Share based compensation - Options Exercised (Details) - USD ($) | 12 Months Ended | ||
|---|---|---|---|
| Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | |
| Share based compensation | |||
| Option Exercised (in shares) | 8,976,462 | 14,614,410 | 5,823,534 | 
| Intrinsic value of stock options exercised | $ 1,281,000 | $ 2,527,000 | $ 2,368,000 | 
| Proceeds from exercise of stock options | 77,000 | 256,000 | 50,000 | 
| Tax benefit from stock option exercises | $ 617,000 | $ 541,000 | $ 488,000 | 
| X | ||||||||||
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- Definition Amount of tax benefit from exercise of option under share-based payment arrangement. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Amount of cash inflow from exercise of option under share-based payment arrangement. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- References No definition available. 
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| X | ||||||||||
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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| X | ||||||||||
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- Definition Number of share options (or share units) exercised during the current period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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