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, 2024 USD ($) claim	Dec. 31, 2023 USD ($)	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 ($)	Dec. 31, 2015 USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 8,296
IBNR	3,215
2015
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	656	$ 639	$ 625	$ 617	$ 602	$ 600	$ 589	$ 574	$ 576	$ 581
IBNR	$ 39
Cumulative Number of Claims | claim	24,309
2016
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 712	704	684	683	673	671	667	659	$ 623
IBNR	$ 27
Cumulative Number of Claims | claim	24,901
2017
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 713	690	652	630	634	632	632	$ 632
IBNR	$ 16
Cumulative Number of Claims | claim	22,544
2018
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 665	679	650	639	646	644	$ 653
IBNR	$ 83
Cumulative Number of Claims | claim	20,553
2019
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 727	720	691	682	682	$ 680
IBNR	$ 129
Cumulative Number of Claims | claim	19,907
2020
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 702	736	726	722	$ 723
IBNR	$ 237
Cumulative Number of Claims | claim	14,964
2021
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 814	793	784	$ 782
IBNR	$ 299
Cumulative Number of Claims | claim	15,952
2022
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 930	928	$ 929
IBNR	$ 515
Cumulative Number of Claims | claim	17,527
2023
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 1,106	$ 1,071
IBNR	$ 726
Cumulative Number of Claims | claim	17,037
2024
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 1,271
IBNR	$ 1,144
Cumulative Number of Claims | claim	14,632