Supplementary Insurance Information - Table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	$ 267	$ 244	$ 322
Reserves for claims and unpaid losses and LAE	11,074	10,392	10,232
Unearned premiums	3,041	2,803	2,830
Net earned premiums	5,404	5,099	5,185
Net investment income	730	461	532
Claims, losses and settlement expenses	3,157	3,271	3,271
Amortization of deferred policy acquisition costs	580	615	721
Other operating expenses	1,480	1,544	1,587
Net written premiums	5,573	5,013	5,342
Property and casualty insurance
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	267	244	322
Reserves for claims and unpaid losses and LAE	11,074	10,392	10,232
Unearned premiums	3,041	2,803	2,830
Net earned premiums	5,404	5,099	5,185
Net investment income	663	399	472
Claims, losses and settlement expenses	3,157	3,271	3,271
Amortization of deferred policy acquisition costs	580	615	721
Other operating expenses	967	1,036	1,027
Net written premiums	5,573	5,013	5,342
Other
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Net investment income	67	62	60
Other operating expenses	$ 513	$ 508	$ 560