Claim and Claim Adjustment Expense Reserves (Commercial - General Liability - Net Incurred Claims and Allocated Claim Adjustment Expenses) (Details) - General Liability - Commercial $ in Millions	Dec. 31, 2025 USD ($) claim	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 9,151
IBNR	3,410
2016
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	723	$ 712	$ 704	$ 684	$ 683	$ 673	$ 671	$ 667	$ 659	$ 623
IBNR	$ 23
Cumulative Number of Claims | claim	24,982
2017
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 749	713	690	652	630	634	632	632	$ 632
IBNR	$ 15
Cumulative Number of Claims | claim	22,611
2018
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 663	665	679	650	639	646	644	$ 653
IBNR	$ 63
Cumulative Number of Claims | claim	20,631
2019
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 747	727	720	691	682	682	$ 680
IBNR	$ 98
Cumulative Number of Claims | claim	20,091
2020
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 662	702	736	726	722	$ 723
IBNR	$ 139
Cumulative Number of Claims | claim	15,152
2021
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 833	814	793	784	$ 782
IBNR	$ 189
Cumulative Number of Claims | claim	16,349
2022
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 952	930	928	$ 929
IBNR	$ 316
Cumulative Number of Claims | claim	18,494
2023
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 1,146	1,106	$ 1,071
IBNR	$ 516
Cumulative Number of Claims | claim	18,905
2024
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 1,295	$ 1,271
IBNR	$ 833
Cumulative Number of Claims | claim	20,250
2025
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 1,381
IBNR	$ 1,218
Cumulative Number of Claims | claim	15,771