Claim and Claim Adjustment Expense Reserves and Future Policy Benefit Reserves - Net Liability for Unpaid Claim and Claim Adjustment Expenses (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net Liability for Unpaid Claim and Claim Adjustment Expenses [Abstract]
Net claim and claim adjustment expenses	$ 19,908	$ 19,205	$ 18,701	$ 17,885
Total reinsurance receivables	5,191	4,969	4,005	3,835
Total gross liability for unpaid claims and claims adjustment expenses	25,099	24,174	$ 22,706	$ 21,720
Property and casualty
Net Liability for Unpaid Claim and Claim Adjustment Expenses [Abstract]
Net claim and claim adjustment expenses	15,996	15,270
Total reinsurance receivables	2,680
Other insurance
Net Liability for Unpaid Claim and Claim Adjustment Expenses [Abstract]
Net claim and claim adjustment expenses	3,912	$ 3,935
Total reinsurance receivables	$ 2,511