Reinsurance and Indemnification - Claims expense, life contract benefits and interest credited to contractholder funds (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Property and casualty insurance claims and claims expense
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ (925)	$ (1,458)	$ (1,300)	$ (3,209)
Property and casualty insurance claims and claims expense | Michigan Catastrophic Claim Association
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred			100	525
Property and casualty insurance claims and claims expense | Florida Excess Catastrophe Reinsurance Program
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	305		305
Accident, health and other policy benefits
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ (5)	$ (13)	$ (21)	(68)
Accident, health and other policy benefits | Nationwide Catastrophe Reinsurance Program
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred				1,400
Accident, health and other policy benefits | National Flood Insurance Program
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred				$ 185