Allowance for Expected Credit Losses - Reinsurance recoverables (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Credit Loss [Abstract]
Balance at beginning of period	$ 9,732	$ 8,969	$ 9,526	$ 8,260
Balance at end of period	9,964	9,044	9,964	9,044
Allowance for Expected Credit Losses
Balance at beginning of period	18	17	17	17
Change for provision of expected credit losses	0	2	1	2
Balance at end of period	$ 18	$ 19	$ 18	$ 19

Amount, after valuation allowance, recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, policy benefits and policy reserves. Excludes premiums paid under reinsurance contracts.