Claim and Claim Adjustment Expense Reserves - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Loss from catastrophes, net of reinsurance	$ 37	$ 54	$ 57	$ 179
Pretax favorable development	(27)	(29)	(15)	(14)
Commercial Property And Casualty Operations
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Pretax favorable development	$ 37	$ 11	$ 49	$ 26