Taxation (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Tax Examination [Line Items]
Income Taxes Receivable, Current	$ 246	$ 266
Taxes Payable, Current	376	330
Deferred Tax Asset, Debt Securities, Trading, Unrealized Loss	787	662
Valuation allowance	1,081	716
Loss carry-forwards	146	149
Unrecognized Tax Benefits	130	73	$ 67
Income Tax Credits and Adjustments	18	19
Unrecognized tax benefits that would affect the effective tax rate	112	54
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	6	7	$ 4
Liabilities recorded for tax-related interest and penalties	30	$ 25
Investments
Income Tax Examination [Line Items]
Valuation allowance	633
Domestic Tax Authority [Member]
Income Tax Examination [Line Items]
Net operating loss carry-forwards	500
Loss carry-forwards	$ 26
SWITZERLAND
Income Tax Examination [Line Items]
Applicable income tax rates	19.70%
Bermuda
Income Tax Examination [Line Items]
Applicable income tax rates	0.00%
UNITED STATES
Income Tax Examination [Line Items]
Applicable income tax rates	21.00%
UNITED KINGDOM
Income Tax Examination [Line Items]
Applicable income tax rates	25.00%

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible capital loss carryforwards.

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Carrying amount due within one year of the balance sheet date (or one operating cycle, if longer) from tax authorities as of the balance sheet date representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes.

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