| Geographic and segmental information - Long lived assets (Details) - USD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023 | 
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| Revenues from External Customers and Long-Lived Assets [Line Items] | ||
| Long-lived assets | $ 51,218 | $ 71,708 | 
| UK | ||
| Revenues from External Customers and Long-Lived Assets [Line Items] | ||
| Long-lived assets | 24,264 | 40,988 | 
| US | ||
| Revenues from External Customers and Long-Lived Assets [Line Items] | ||
| Long-lived assets | $ 26,954 | $ 30,720 | 
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- Definition Long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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