Claim and Claim Adjustment Expense Reserves and Future Policy Benefit Reserves (Commercial - General Liability - Net Incurred Claims and Allocated Claim Adjustment Expenses) (Details) - General Liability - Commercial $ in Millions	Dec. 31, 2022 USD ($) claim	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 7,046
IBNR	2,324
2013
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	629	$ 624	$ 623	$ 620	$ 623	$ 613	$ 655	$ 650	$ 655	$ 650
IBNR	$ 32
Cumulative Number of Claims | claim	33,738
2014
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 676	659	659	658	635	631	654	658	$ 653
IBNR	$ 34
Cumulative Number of Claims | claim	28,131
2015
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 625	617	602	600	589	574	576	$ 581
IBNR	$ 33
Cumulative Number of Claims | claim	24,200
2016
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 684	683	673	671	667	659	$ 623
IBNR	$ 43
Cumulative Number of Claims | claim	24,699
2017
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 652	630	634	632	632	$ 632
IBNR	$ 32
Cumulative Number of Claims | claim	22,359
2018
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 650	639	646	644	$ 653
IBNR	$ 127
Cumulative Number of Claims | claim	20,242
2019
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 691	682	682	$ 680
IBNR	$ 227
Cumulative Number of Claims | claim	19,265
2020
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 726	722	$ 723
IBNR	$ 434
Cumulative Number of Claims | claim	13,998
2021
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 784	$ 782
IBNR	$ 527
Cumulative Number of Claims | claim	13,775
2022
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 929
IBNR	$ 835
Cumulative Number of Claims | claim	10,572