Insurance Liabilities - Net loss reserve discount benefit (charge) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Net Loss Reserve Discount Benefit (Charge) [Line Items]
Current accident year	$ 24	$ 12	$ 48	$ 26
Accretion and other adjustments to prior year discount	(38)	(34)	(42)	(16)
Net reserve discount benefit (charge)	(14)	(22)	6	10
Change in discount on loss reserves ceded under retroactive reinsurance	18	17	57	56
Net change in total reserve discount	4	(5)	63	66
United Kingdom
Net Loss Reserve Discount Benefit (Charge) [Line Items]
Net change in total reserve discount	$ 7	$ (2)	$ 5	$ (9)