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Income Taxes - Operating and capital loss carryforwards available (Details) - Dec. 31, 2024 £ in Millions, $ in Millions | USD ($) | GBP (£)
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U.S. | Expiring 2025 - 2041 |  |
Operating and capital loss carryforwards [Line Items] |  |
Operating loss carryforwards | $ 8 |
United Kingdom |  |
Operating and capital loss carryforwards [Line Items] |  |
Operating loss carryforwards | $ 35 | £ 28

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