Insurance Liabilities - Discounting of reserves (Details) - USD ($)	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Discounting of Reserves [Line Items]
U.S. workers' compensation	$ 2,447,000,000		$ 2,532,000,000
Retroactive reinsurance	(1,134,000,000)		(1,254,000,000)
Total reserve discount	1,313,000,000		1,278,000,000
Fortitude RE
Discounting of Reserves [Line Items]
Total reserve discount	$ 740,000,000		763,000,000
Discount ceded on sale (as a percent)	100.00%	100.00%
United Kingdom
Discounting of Reserves [Line Items]
Total reserve discount	$ 150,000,000		$ 135,000,000