Insurance Liabilities - Net Loss Reserve Discount Benefit (Charge) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Net Loss Reserve Discount Benefit (Charge) [Line Items]
Current accident year	$ 33	$ 36	$ 56	$ 66
Accretion and other adjustments to prior year discount	(45)	(62)	(85)	(168)
Net reserve discount benefit (charge)	(12)	(26)	(29)	(102)
Change in discount on loss reserves ceded under retroactive reinsurance	19	23	20	78
Net change in total reserve discount	7	(3)	(9)	(24)
United Kingdom
Net Loss Reserve Discount Benefit (Charge) [Line Items]
Net change in total reserve discount	$ 11	$ 2	$ 17	$ 0