Insurance Liabilities - Net Loss Reserve Discount Benefit (Charge) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Net Loss Reserve Discount Benefit (Charge) [Line Items]
Current accident year	$ 30	$ 30
Accretion and other adjustments to prior year discount	(106)	(94)
Net reserve discount benefit (charge)	(76)	(64)
Change in discount on loss reserves ceded under retroactive reinsurance	55	70
Net change in total reserve discount	(21)	6
United Kingdom
Net Loss Reserve Discount Benefit (Charge) [Line Items]
Net change in total reserve discount	$ (2)	$ 4