Supplementary Insurance Information - Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	$ 288	$ 267	$ 244
Reserves for claims and unpaid losses and LAE	11,974	11,074	10,392
Unearned premiums	3,246	3,041	2,803
Net earned premiums	6,085	5,404	5,099
Net investment income	717	730	461
Claims, losses and settlement expenses	3,629	3,157	3,271
Amortization of deferred policy acquisition costs	641	580	615
Other operating expenses	1,647	1,480	1,544
Net written premiums	6,206	5,573	5,013
Property and casualty insurance
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	288	267	244
Reserves for claims and unpaid losses and LAE	11,974	11,074	10,392
Unearned premiums	3,246	3,041	2,803
Net earned premiums	6,085	5,404	5,099
Net investment income	683	663	399
Claims, losses and settlement expenses	3,629	3,157	3,271
Amortization of deferred policy acquisition costs	641	580	615
Other operating expenses	1,091	967	1,036
Net written premiums	6,206	5,573	5,013
Other
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Net investment income	34	67	62
Other operating expenses	$ 556	$ 513	$ 508