Insurance Liabilities - Net loss reserve discount benefit (charge) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Net Loss Reserve Discount Benefit (Charge) [Line Items]
Current accident year	$ 47	$ 26	$ 115	$ 74
Accretion and other adjustments to prior year discount	(52)	(36)	(200)	(78)
Net reserve discount benefit (charge)	(5)	(10)	(85)	(4)
Change in discount on loss reserves ceded under retroactive reinsurance	24	17	120	74
Net change in total reserve discount	19	7	35	70
United Kingdom
Net Loss Reserve Discount Benefit (Charge) [Line Items]
Net change in total reserve discount	$ 7	$ 20	$ 15	$ 15