Claim and Claim Adjustment Expense Reserves - Net Liability for Unpaid Claim and Claim Adjustment Expenses (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Net Liability for Unpaid Claim and Claim Adjustment Expenses [Abstract]
Net claim and claim adjustment expenses	$ 20,617	$ 19,263	$ 18,163	$ 16,929
Total reinsurance receivables	5,982	5,713	5,141	5,191
Total gross liability for unpaid claims and claims adjustment expenses	26,599	24,976	$ 23,304	$ 22,120
Property and casualty
Net Liability for Unpaid Claim and Claim Adjustment Expenses [Abstract]
Net claim and claim adjustment expenses	19,725	18,334
Total reinsurance receivables	3,684
Other insurance
Net Liability for Unpaid Claim and Claim Adjustment Expenses [Abstract]
Net claim and claim adjustment expenses	892	$ 929
Total reinsurance receivables	$ 2,298