Claim and Claim Adjustment Expense Reserves (International - Excluding Hardy - Net Incurred Claims and Allocated Claim Adjustment Expenses) (Details) - Excluding Hardy - International $ in Millions	Dec. 31, 2023 USD ($) claim	Dec. 31, 2022 USD ($)	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 ($)	Dec. 31, 2014 USD ($)
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 3,682
IBNR	1,073
2014
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	288	$ 286	$ 283	$ 290	$ 289	$ 272	$ 279	$ 291	$ 291	$ 276
IBNR	$ 15
Cumulative Number of Claims | claim	25,130
2015
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 281	285	285	283	280	286	303	304	$ 289
IBNR	$ 19
Cumulative Number of Claims | claim	23,608
2016
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 309	292	290	276	285	288	302	$ 284
IBNR	$ 36
Cumulative Number of Claims | claim	18,079
2017
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 393	360	371	376	383	363	$ 299
IBNR	$ 39
Cumulative Number of Claims | claim	18,841
2018
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 411	401	388	389	385	$ 367
IBNR	$ 48
Cumulative Number of Claims | claim	21,327
2019
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 362	360	352	355	$ 342
IBNR	$ 61
Cumulative Number of Claims | claim	18,993
2020
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 347	362	372	$ 381
IBNR	$ 107
Cumulative Number of Claims | claim	15,744
2021
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 375	397	$ 408
IBNR	$ 162
Cumulative Number of Claims | claim	15,136
2022
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 438	$ 428
IBNR	$ 227
Cumulative Number of Claims | claim	11,899
2023
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items]
Incurred claims and allocated claim adjustment expense, net	$ 478
IBNR	$ 359
Cumulative Number of Claims | claim	7,869