Reinsurance and Indemnification - Claims expense, life contract benefits and interest credited to contractholder funds (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Property and casualty insurance claims and claims expense
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ (406)	$ (158)	$ (515)	$ (1,751)
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			44	450
Accident, health and other policy benefits
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred	$ (9)	$ (26)	$ (16)	(55)
Accident, health and other policy benefits | Nationwide Catastrophe Reinsurance Program
Reductions to costs and expenses due to reinsurance ceded amounts
Ceded losses incurred				$ 675