Insurance Liabilities - Undiscounted, Incurred and Paid Losses and Allocated Loss Adjustment Expenses (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) country	Dec. 31, 2022 USD ($)	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 ($)	Dec. 31, 2014 USD ($)
Liability for Claims and Claims Adjustment Expense [Line Items]
2023 Prior Year Development Excluding the Impact of ADC	$ (392)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(234)
U.S. Workers' Compensation (before discount)
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	8,589
2023 Prior Year Development Excluding the Impact of ADC	(267)
Incurred Impact of ADC	(4,301)
2023 (Net of Impact of ADC)	7,802
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	4,727
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	4,327
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	8,189
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(114)
Paid Impact of ADC	$ (118)
Year 1 (as a percent)	11.90%
Year 2 (as a percent)	17.20%
Year 3 (as a percent)	11.00%
Year 4 (as a percent)	7.20%
Year 5 (as a percent)	4.80%
Year 6 (as a percent)	3.20%
Year 7 (as a percent)	2.00%
Year 8 (as a percent)	1.70%
Year 9 (as a percent)	1.50%
Year 10 (as a percent)	1.20%
U.S. Workers' Compensation (before discount) | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 118
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(3,632)
Unallocated loss adjustment expense prior year development	32
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	153
U.S. Workers' Compensation (before discount) | 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,589	$ 1,614	$ 1,637	$ 1,679	$ 1,709	$ 1,794	$ 1,862	$ 1,866	$ 1,764	$ 1,729
2023 Prior Year Development Excluding the Impact of ADC	(25)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 172
Cumulative Number of Reported Claims | country	41,529
Incurred Impact of ADC	$ (349)
IBNR Impact of ADC	(143)
2023 (Net of Impact of ADC)	1,240	1,243	1,171	1,223	1,329	1,309	1,310	1,311
Total of IBNR Liabilities Net of Impact of ADC	29
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,226	1,207	1,180	1,137	1,096	1,030	930	786	558	231
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(3)
Paid Impact of ADC	(64)
U.S. Workers' Compensation (before discount) | 2014 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(349)	(371)	(466)	(456)	(380)	(485)	(552)	(555)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	22
U.S. Workers' Compensation (before discount) | 2015
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,592	1,612	1,634	1,675	1,722	1,814	1,866	1,864	1,708
2023 Prior Year Development Excluding the Impact of ADC	(20)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 355
Cumulative Number of Reported Claims | country	37,109
Incurred Impact of ADC	$ (438)
IBNR Impact of ADC	(228)
2023 (Net of Impact of ADC)	1,154	1,092	1,041	1,105	1,134	1,318	1,279	1,279
Total of IBNR Liabilities Net of Impact of ADC	127
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,058	1,038	1,013	979	925	854	725	524	234
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	62
Paid Impact of ADC	(54)
U.S. Workers' Compensation (before discount) | 2015 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(438)	(520)	(593)	(570)	(588)	(496)	(587)	(585)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	82
U.S. Workers' Compensation (before discount) | 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,025	1,036	1,075	1,090	1,140	1,318	1,346	1,299
2023 Prior Year Development Excluding the Impact of ADC	(11)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 224
Cumulative Number of Reported Claims | country	31,868
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,025	1,036	1,075	1,090	1,140	1,318	1,346	1,299
Total of IBNR Liabilities Net of Impact of ADC	224
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	694	686	662	630	584	521	378	147
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(11)
Paid Impact of ADC	0
U.S. Workers' Compensation (before discount) | 2016 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Workers' Compensation (before discount) | 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	705	712	731	763	776	850	789
2023 Prior Year Development Excluding the Impact of ADC	(7)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 218
Cumulative Number of Reported Claims | country	27,695
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	705	712	731	763	776	850	789
Total of IBNR Liabilities Net of Impact of ADC	218
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	395	389	367	333	294	224	93
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(7)
Paid Impact of ADC	0
U.S. Workers' Compensation (before discount) | 2017 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Workers' Compensation (before discount) | 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	875	896	911	961	1,021	998
2023 Prior Year Development Excluding the Impact of ADC	(21)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 385
Cumulative Number of Reported Claims | country	22,222
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	875	896	911	961	1,021	998
Total of IBNR Liabilities Net of Impact of ADC	385
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	409	388	359	296	215	85
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(21)
Paid Impact of ADC	0
U.S. Workers' Compensation (before discount) | 2018 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Workers' Compensation (before discount) | 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	788	801	812	873	887
2023 Prior Year Development Excluding the Impact of ADC	(13)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 285
Cumulative Number of Reported Claims | country	17,000
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	788	801	812	873	887
Total of IBNR Liabilities Net of Impact of ADC	285
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	389	347	301	219	93
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(13)
Paid Impact of ADC	0
U.S. Workers' Compensation (before discount) | 2019 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Workers' Compensation (before discount) | 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	477	521	573	597
2023 Prior Year Development Excluding the Impact of ADC	(44)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 106
Cumulative Number of Reported Claims | country	13,839
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	477	521	573	597
Total of IBNR Liabilities Net of Impact of ADC	106
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	245	205	159	64
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(44)
Paid Impact of ADC	0
U.S. Workers' Compensation (before discount) | 2020 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Workers' Compensation (before discount) | 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	545	570	597
2023 Prior Year Development Excluding the Impact of ADC	(25)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 274
Cumulative Number of Reported Claims | country	10,982
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	545	570	597
Total of IBNR Liabilities Net of Impact of ADC	274
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	171	128	60
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(25)
Paid Impact of ADC	0
U.S. Workers' Compensation (before discount) | 2021 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Workers' Compensation (before discount) | 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	493	523
2023 Prior Year Development Excluding the Impact of ADC	(30)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 296
Cumulative Number of Reported Claims | country	9,339
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	493	523
Total of IBNR Liabilities Net of Impact of ADC	296
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	102	45
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(30)
Paid Impact of ADC	0
U.S. Workers' Compensation (before discount) | 2022 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Workers' Compensation (before discount) | 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	500
2023 Prior Year Development Excluding the Impact of ADC
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 397
Cumulative Number of Reported Claims | country	7,359
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	500
Total of IBNR Liabilities Net of Impact of ADC	397
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	38
Prior Year Development Net of External Reinsurance After ADC Cessions(a)
Paid Impact of ADC	0
U.S. Workers' Compensation (before discount) | 2023 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Workers' Compensation (before discount) | Short Duration Insurance Contracts Last Ten Accident Years
Liability for Claims and Claims Adjustment Expense [Line Items]
2023 Prior Year Development Excluding the Impact of ADC	(196)
Incurred Impact of ADC	(787)
2023 (Net of Impact of ADC)	7,802	7,394	6,911	6,612	6,287	5,793	4,724	3,889
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(92)
U.S. Workers' Compensation (before discount) | Short Duration Insurance Contracts Last Ten Accident Years | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(787)	(891)	(1,059)	(1,026)	(968)	(981)	(1,139)	(1,140)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	104
U.S. Workers' Compensation (before discount) | Shortduration Insurance Contracts Accident Years Prior To Current Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	0
U.S. Workers' Compensation (before discount) | Incurred Impact Of Adverse Development Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	118
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(3,632)
U.S. Workers' Compensation (before discount) | Short Duration Insurance Contracts Accident Years Prior To2012
Liability for Claims and Claims Adjustment Expense [Line Items]
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(65)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(48)
U.S. Workers' Compensation (before discount) | Short Duration Insurance Contracts Accident Years Prior To2012 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	17
U.S. Workers' Compensation (before discount) | Net Of Impact Of Adverse Development Reinsurance Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	4,609
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	695
Unallocated loss adjustment expense prior year development	26
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	3,888
U.S. Workers' Compensation (before discount) | Unallocated To Accident Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Unallocated loss adjustment expense prior year development	(6)
U.S. Excess Casualty
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	8,084
2023 Prior Year Development Excluding the Impact of ADC	(32)
Incurred Impact of ADC	(2,083)
2023 (Net of Impact of ADC)	7,238
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	4,724
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	2,044
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	5,404
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	18
Paid Impact of ADC	$ (251)
Year 1 (as a percent)	1.20%
Year 2 (as a percent)	8.50%
Year 3 (as a percent)	9.20%
Year 4 (as a percent)	18.10%
Year 5 (as a percent)	10.50%
Year 6 (as a percent)	7.90%
Year 7 (as a percent)	7.40%
Year 8 (as a percent)	6.60%
Year 9 (as a percent)	2.70%
Year 10 (as a percent)	1.90%
U.S. Excess Casualty | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 251
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(1,488)
Unallocated loss adjustment expense prior year development	30
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	50
U.S. Excess Casualty | 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,245	1,259	1,269	1,248	1,283	1,339	1,260	1,275	1,069	938
2023 Prior Year Development Excluding the Impact of ADC	(14)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 277
Cumulative Number of Reported Claims | country	2,985
Incurred Impact of ADC	$ (384)
IBNR Impact of ADC	(144)
2023 (Net of Impact of ADC)	861	869	949	912	844	915	905	902
Total of IBNR Liabilities Net of Impact of ADC	133
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	902	878	839	815	703	590	444	240	77	3
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(8)
Paid Impact of ADC	(80)
U.S. Excess Casualty | 2014 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(384)	(390)	(320)	(336)	(439)	(424)	(355)	(373)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	6
U.S. Excess Casualty | 2015
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,658	1,686	1,721	1,694	1,656	1,603	1,440	1,463	989
2023 Prior Year Development Excluding the Impact of ADC	(28)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 258
Cumulative Number of Reported Claims | country	3,142
Incurred Impact of ADC	$ (462)
IBNR Impact of ADC	(116)
2023 (Net of Impact of ADC)	1,196	1,174	1,231	1,211	1,163	1,139	1,015	1,027
Total of IBNR Liabilities Net of Impact of ADC	142
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,291	1,253	1,124	1,061	935	718	391	210	9
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	22
Paid Impact of ADC	(171)
U.S. Excess Casualty | 2015 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(462)	(512)	(490)	(483)	(493)	(464)	(425)	(436)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	50
U.S. Excess Casualty | 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,276	1,263	1,250	1,274	1,171	1,162	1,146	898
2023 Prior Year Development Excluding the Impact of ADC	13
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 314
Cumulative Number of Reported Claims | country	2,813
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,276	1,263	1,250	1,274	1,171	1,162	1,146	898
Total of IBNR Liabilities Net of Impact of ADC	314
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	798	670	566	502	388	204	80	28
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	13
Paid Impact of ADC	0
U.S. Excess Casualty | 2016 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Excess Casualty | 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,182	1,200	1,157	1,153	1,097	1,002	856
2023 Prior Year Development Excluding the Impact of ADC	(18)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 264
Cumulative Number of Reported Claims | country	2,079
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,182	1,200	1,157	1,153	1,097	1,002	856
Total of IBNR Liabilities Net of Impact of ADC	264
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	781	676	585	505	156	45	1
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(18)
Paid Impact of ADC	0
U.S. Excess Casualty | 2017 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Excess Casualty | 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	779	769	769	721	646	648
2023 Prior Year Development Excluding the Impact of ADC	10
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 155
Cumulative Number of Reported Claims | country	1,461
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	779	769	769	721	646	648
Total of IBNR Liabilities Net of Impact of ADC	155
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	494	414	315	227	125	1
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	10
Paid Impact of ADC	0
U.S. Excess Casualty | 2018 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Excess Casualty | 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	600	612	597	583	577
2023 Prior Year Development Excluding the Impact of ADC	(12)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 301
Cumulative Number of Reported Claims | country	1,347
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	600	612	597	583	577
Total of IBNR Liabilities Net of Impact of ADC	301
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	216	157	79	43	7
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(12)
Paid Impact of ADC	0
U.S. Excess Casualty | 2019 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Excess Casualty | 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	420	410	413	406
2023 Prior Year Development Excluding the Impact of ADC	10
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 238
Cumulative Number of Reported Claims | country	1,284
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	420	410	413	406
Total of IBNR Liabilities Net of Impact of ADC	238
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	128	33	15	4
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	10
Paid Impact of ADC	0
U.S. Excess Casualty | 2020 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Excess Casualty | 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	274	277	278
2023 Prior Year Development Excluding the Impact of ADC	(3)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 100
Cumulative Number of Reported Claims | country	855
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	274	277	278
Total of IBNR Liabilities Net of Impact of ADC	100
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	62	43	4
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(3)
Paid Impact of ADC	0
U.S. Excess Casualty | 2021 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Excess Casualty | 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	305	305
2023 Prior Year Development Excluding the Impact of ADC	0
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 189
Cumulative Number of Reported Claims | country	490
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	305	305
Total of IBNR Liabilities Net of Impact of ADC	189
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	51	14
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
Paid Impact of ADC	0
U.S. Excess Casualty | 2022 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Excess Casualty | 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	345
2023 Prior Year Development Excluding the Impact of ADC
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 326
Cumulative Number of Reported Claims | country	303
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	345
Total of IBNR Liabilities Net of Impact of ADC	326
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1
Prior Year Development Net of External Reinsurance After ADC Cessions(a)
Paid Impact of ADC	0
U.S. Excess Casualty | 2023 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Excess Casualty | Short Duration Insurance Contracts Last Ten Accident Years
Liability for Claims and Claims Adjustment Expense [Line Items]
2023 Prior Year Development Excluding the Impact of ADC	(42)
Incurred Impact of ADC	(846)
2023 (Net of Impact of ADC)	7,238	6,879	6,644	6,260	5,498	4,866	3,922	2,827
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	14
U.S. Excess Casualty | Short Duration Insurance Contracts Last Ten Accident Years | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(846)	(902)	(810)	(819)	(932)	(888)	(780)	(809)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	56
U.S. Excess Casualty | Shortduration Insurance Contracts Accident Years Prior To Current Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	0
U.S. Excess Casualty | Incurred Impact Of Adverse Development Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	251
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(1,488)
U.S. Excess Casualty | Short Duration Insurance Contracts Accident Years Prior To2012
Liability for Claims and Claims Adjustment Expense [Line Items]
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(75)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(111)
U.S. Excess Casualty | Short Duration Insurance Contracts Accident Years Prior To2012 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(36)
U.S. Excess Casualty | Net Of Impact Of Adverse Development Reinsurance Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	(4,473)
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	556
Unallocated loss adjustment expense prior year development	115
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	3,321
U.S. Excess Casualty | Unallocated To Accident Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Unallocated loss adjustment expense prior year development	85
U.S. Other Casualty
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	10,583
2023 Prior Year Development Excluding the Impact of ADC	(133)
Incurred Impact of ADC	(1,251)
2023 (Net of Impact of ADC)	10,087
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	6,668
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	1,448
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	5,363
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(133)
Paid Impact of ADC	$ (298)
Year 1 (as a percent)	5.80%
Year 2 (as a percent)	11.30%
Year 3 (as a percent)	14.20%
Year 4 (as a percent)	14.40%
Year 5 (as a percent)	13.70%
Year 6 (as a percent)	9.40%
Year 7 (as a percent)	6.70%
Year 8 (as a percent)	4.00%
Year 9 (as a percent)	2.80%
Year 10 (as a percent)	0.50%
U.S. Other Casualty | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 298
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(1,053)
Unallocated loss adjustment expense prior year development	24
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Other Casualty | 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,905	1,944	1,935	1,946	1,916	1,910	2,009	1,963	1,721	1,751
2023 Prior Year Development Excluding the Impact of ADC	(39)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 46
Cumulative Number of Reported Claims | country	38,546
Incurred Impact of ADC	$ (214)
IBNR Impact of ADC	(29)
2023 (Net of Impact of ADC)	1,691	1,718	1,722	1,701	1,694	1,634	1,678	1,667
Total of IBNR Liabilities Net of Impact of ADC	17
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,805	1,795	1,719	1,653	1,572	1,392	1,150	868	620	210
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(27)
Paid Impact of ADC	(122)
U.S. Other Casualty | 2014 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(214)	(226)	(213)	(245)	(222)	(276)	(331)	(296)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	12
U.S. Other Casualty | 2015
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,796	1,815	1,824	1,834	1,794	1,736	1,829	1,762	1,329
2023 Prior Year Development Excluding the Impact of ADC	(19)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 23
Cumulative Number of Reported Claims | country	35,754
Incurred Impact of ADC	$ (282)
IBNR Impact of ADC	(8)
2023 (Net of Impact of ADC)	1,514	1,563	1,562	1,553	1,493	1,423	1,373	1,361
Total of IBNR Liabilities Net of Impact of ADC	15
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,707	1,680	1,603	1,485	1,351	1,087	769	309	105
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(49)
Paid Impact of ADC	(176)
U.S. Other Casualty | 2015 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(282)	(252)	(262)	(281)	(301)	(313)	(456)	(401)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(30)
U.S. Other Casualty | 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,297	1,293	1,323	1,340	1,391	1,321	1,343	1,339
2023 Prior Year Development Excluding the Impact of ADC	4
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 162
Cumulative Number of Reported Claims | country	29,191
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,297	1,293	1,323	1,340	1,391	1,321	1,343	1,339
Total of IBNR Liabilities Net of Impact of ADC	162
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,074	1,018	938	846	703	489	298	77
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	4
Paid Impact of ADC	0
U.S. Other Casualty | 2016 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Other Casualty | 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	654	643	668	674	738	629	602
2023 Prior Year Development Excluding the Impact of ADC	11
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 21
Cumulative Number of Reported Claims | country	21,266
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	654	643	668	674	738	629	602
Total of IBNR Liabilities Net of Impact of ADC	21
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	592	527	455	314	216	111	51
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	11
Paid Impact of ADC	0
U.S. Other Casualty | 2017 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Other Casualty | 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	810	824	870	837	845	802
2023 Prior Year Development Excluding the Impact of ADC	(14)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 148
Cumulative Number of Reported Claims | country	16,967
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	810	824	870	837	845	802
Total of IBNR Liabilities Net of Impact of ADC	148
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	565	470	360	227	122	43
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(14)
Paid Impact of ADC	0
U.S. Other Casualty | 2018 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Other Casualty | 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,039	1,062	1,053	1,058	1,059
2023 Prior Year Development Excluding the Impact of ADC	(23)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 526
Cumulative Number of Reported Claims | country	21,036
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,039	1,062	1,053	1,058	1,059
Total of IBNR Liabilities Net of Impact of ADC	526
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	410	321	226	138	53
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(23)
Paid Impact of ADC	0
U.S. Other Casualty | 2019 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Other Casualty | 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	540	538	576	524
2023 Prior Year Development Excluding the Impact of ADC	2
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 277
Cumulative Number of Reported Claims | country	11,318
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	540	538	576	524
Total of IBNR Liabilities Net of Impact of ADC	277
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	198	139	73	26
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	2
Paid Impact of ADC	0
U.S. Other Casualty | 2020 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Other Casualty | 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	790	793	795
2023 Prior Year Development Excluding the Impact of ADC	(3)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 519
Cumulative Number of Reported Claims | country	10,572
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	790	793	795
Total of IBNR Liabilities Net of Impact of ADC	519
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	169	87	32
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(3)
Paid Impact of ADC	0
U.S. Other Casualty | 2021 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Other Casualty | 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	819	793
2023 Prior Year Development Excluding the Impact of ADC	26
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 617
Cumulative Number of Reported Claims | country	12,457
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	819	793
Total of IBNR Liabilities Net of Impact of ADC	617
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	112	38
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	26
Paid Impact of ADC	0
U.S. Other Casualty | 2022 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Other Casualty | 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	933
2023 Prior Year Development Excluding the Impact of ADC
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 848
Cumulative Number of Reported Claims | country	10,401
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	933
Total of IBNR Liabilities Net of Impact of ADC	848
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	36
Prior Year Development Net of External Reinsurance After ADC Cessions(a)
Paid Impact of ADC	0
U.S. Other Casualty | 2023 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Other Casualty | Short Duration Insurance Contracts Last Ten Accident Years
Liability for Claims and Claims Adjustment Expense [Line Items]
2023 Prior Year Development Excluding the Impact of ADC	(55)
Incurred Impact of ADC	(496)
2023 (Net of Impact of ADC)	10,087	9,227	8,569	7,687	7,220	5,809	4,996	4,367
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(73)
U.S. Other Casualty | Short Duration Insurance Contracts Last Ten Accident Years | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(496)	(478)	(475)	(526)	(523)	(589)	(787)	(697)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(18)
U.S. Other Casualty | Shortduration Insurance Contracts Accident Years Prior To Current Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	0
U.S. Other Casualty | Incurred Impact Of Adverse Development Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	298
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(1,053)
U.S. Other Casualty | Short Duration Insurance Contracts Accident Years Prior To2012
Liability for Claims and Claims Adjustment Expense [Line Items]
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(67)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(73)
U.S. Other Casualty | Short Duration Insurance Contracts Accident Years Prior To2012 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(6)
U.S. Other Casualty | Net Of Impact Of Adverse Development Reinsurance Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	(6,370)
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	395
Unallocated loss adjustment expense prior year development	13
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	4,112
U.S. Other Casualty | Unallocated To Accident Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Unallocated loss adjustment expense prior year development	(11)
U.S. Financial Lines
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	17,560
2023 Prior Year Development Excluding the Impact of ADC	94
Incurred Impact of ADC	(514)
2023 (Net of Impact of ADC)	16,768
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	11,645
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	271
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	6,186
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	50
Paid Impact of ADC	$ (501)
Year 1 (as a percent)	3.70%
Year 2 (as a percent)	14.60%
Year 3 (as a percent)	18.20%
Year 4 (as a percent)	15.60%
Year 5 (as a percent)	12.50%
Year 6 (as a percent)	8.10%
Year 7 (as a percent)	6.10%
Year 8 (as a percent)	5.80%
Year 9 (as a percent)	3.90%
Year 10 (as a percent)	1.40%
U.S. Financial Lines | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 501
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(223)
Unallocated loss adjustment expense prior year development	4
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(44)
U.S. Financial Lines | 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,017	2,014	2,057	2,000	1,981	1,960	1,927	1,892	1,777	1,812
2023 Prior Year Development Excluding the Impact of ADC	3
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 91
Cumulative Number of Reported Claims | country	17,650
Incurred Impact of ADC	$ (297)
IBNR Impact of ADC	(68)
2023 (Net of Impact of ADC)	1,720	1,738	1,761	1,759	1,741	1,753	1,729	1,733
Total of IBNR Liabilities Net of Impact of ADC	23
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,849	1,820	1,758	1,658	1,573	1,387	1,158	849	366	66
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(18)
Paid Impact of ADC	(147)
U.S. Financial Lines | 2014 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(297)	(276)	(296)	(241)	(240)	(207)	(198)	(159)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(21)
U.S. Financial Lines | 2015
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,048	2,044	1,959	1,874	1,830	1,788	1,743	1,762	1,737
2023 Prior Year Development Excluding the Impact of ADC	4
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 78
Cumulative Number of Reported Claims | country	16,253
Incurred Impact of ADC	$ (495)
IBNR Impact of ADC	(63)
2023 (Net of Impact of ADC)	1,553	1,605	1,595	1,550	1,552	1,462	1,430	1,429
Total of IBNR Liabilities Net of Impact of ADC	15
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,914	1,818	1,686	1,488	1,282	1,055	791	390	63
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(52)
Paid Impact of ADC	(354)
U.S. Financial Lines | 2015 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(495)	(439)	(364)	(324)	(278)	(326)	(313)	(333)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(56)
U.S. Financial Lines | 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,308	2,325	2,281	2,139	2,064	1,993	1,855	1,605
2023 Prior Year Development Excluding the Impact of ADC	(17)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 133
Cumulative Number of Reported Claims | country	16,127
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	2,308	2,325	2,281	2,139	2,064	1,993	1,855	1,605
Total of IBNR Liabilities Net of Impact of ADC	133
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	2,039	1,903	1,826	1,659	1,358	1,002	499	73
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(17)
Paid Impact of ADC	0
U.S. Financial Lines | 2016 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Financial Lines | 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,957	1,987	1,898	1,846	1,756	1,675	1,564
2023 Prior Year Development Excluding the Impact of ADC	(30)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 130
Cumulative Number of Reported Claims | country	15,269
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,957	1,987	1,898	1,846	1,756	1,675	1,564
Total of IBNR Liabilities Net of Impact of ADC	130
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,653	1,515	1,396	1,118	761	391	64
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(30)
Paid Impact of ADC	0
U.S. Financial Lines | 2017 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Financial Lines | 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,322	2,225	2,063	1,882	1,766	1,640
2023 Prior Year Development Excluding the Impact of ADC	97
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 498
Cumulative Number of Reported Claims | country	14,833
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	2,322	2,225	2,063	1,882	1,766	1,640
Total of IBNR Liabilities Net of Impact of ADC	498
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,601	1,415	1,126	835	486	86
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	97
Paid Impact of ADC	0
U.S. Financial Lines | 2018 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Financial Lines | 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,912	1,926	1,627	1,536	1,503
2023 Prior Year Development Excluding the Impact of ADC	(14)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 513
Cumulative Number of Reported Claims | country	13,319
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,912	1,926	1,627	1,536	1,503
Total of IBNR Liabilities Net of Impact of ADC	513
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,204	953	642	367	94
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(14)
Paid Impact of ADC	0
U.S. Financial Lines | 2019 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Financial Lines | 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,457	1,408	1,252	1,213
2023 Prior Year Development Excluding the Impact of ADC	49
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 331
Cumulative Number of Reported Claims | country	10,390
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,457	1,408	1,252	1,213
Total of IBNR Liabilities Net of Impact of ADC	331
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	915	648	356	84
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	49
Paid Impact of ADC	0
U.S. Financial Lines | 2020 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Financial Lines | 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,388	1,408	1,430
2023 Prior Year Development Excluding the Impact of ADC	(20)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 894
Cumulative Number of Reported Claims | country	7,117
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,388	1,408	1,430
Total of IBNR Liabilities Net of Impact of ADC	894
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	315	151	43
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(20)
Paid Impact of ADC	0
U.S. Financial Lines | 2021 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Financial Lines | 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,108	1,130
2023 Prior Year Development Excluding the Impact of ADC	(22)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 948
Cumulative Number of Reported Claims | country	5,809
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,108	1,130
Total of IBNR Liabilities Net of Impact of ADC	948
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	109	30
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(22)
Paid Impact of ADC	0
U.S. Financial Lines | 2022 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Financial Lines | 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,043
2023 Prior Year Development Excluding the Impact of ADC
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 950
Cumulative Number of Reported Claims | country	6,467
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,043
Total of IBNR Liabilities Net of Impact of ADC	950
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	46
Prior Year Development Net of External Reinsurance After ADC Cessions(a)
Paid Impact of ADC	0
U.S. Financial Lines | 2023 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Financial Lines | Short Duration Insurance Contracts Last Ten Accident Years
Liability for Claims and Claims Adjustment Expense [Line Items]
2023 Prior Year Development Excluding the Impact of ADC	50
Incurred Impact of ADC	(792)
2023 (Net of Impact of ADC)	16,768	15,752	13,907	11,925	10,382	8,523	6,578	4,767
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(27)
U.S. Financial Lines | Short Duration Insurance Contracts Last Ten Accident Years | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(792)	(715)	(660)	(565)	(518)	(533)	(511)	(492)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(77)
U.S. Financial Lines | Shortduration Insurance Contracts Accident Years Prior To Current Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	0
U.S. Financial Lines | Incurred Impact Of Adverse Development Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	501
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(223)
U.S. Financial Lines | Short Duration Insurance Contracts Accident Years Prior To2012
Liability for Claims and Claims Adjustment Expense [Line Items]
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	27
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	56
U.S. Financial Lines | Short Duration Insurance Contracts Accident Years Prior To2012 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	29
U.S. Financial Lines | Net Of Impact Of Adverse Development Reinsurance Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	(11,144)
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	48
Unallocated loss adjustment expense prior year development	21
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	5,672
U.S. Financial Lines | Unallocated To Accident Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Unallocated loss adjustment expense prior year development	17
U.S. Property and Special Risks
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	28,412
2023 Prior Year Development Excluding the Impact of ADC	(10)
Incurred Impact of ADC	(211)
2023 (Net of Impact of ADC)	28,260
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	24,207
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	409
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	4,614
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
Paid Impact of ADC	$ (87)
Year 1 (as a percent)	35.20%
Year 2 (as a percent)	32.20%
Year 3 (as a percent)	11.80%
Year 4 (as a percent)	8.10%
Year 5 (as a percent)	4.90%
Year 6 (as a percent)	3.10%
Year 7 (as a percent)	1.80%
Year 8 (as a percent)	1.30%
Year 9 (as a percent)	1.50%
Year 10 (as a percent)	2.30%
U.S. Property and Special Risks | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 87
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(146)
Unallocated loss adjustment expense prior year development	1
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	10
U.S. Property and Special Risks | 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,437	2,440	2,446	2,460	2,477	2,494	2,480	2,490	2,396	2,600
2023 Prior Year Development Excluding the Impact of ADC	(3)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 4
Cumulative Number of Reported Claims | country	60,766
Incurred Impact of ADC	$ (52)
IBNR Impact of ADC	(2)
2023 (Net of Impact of ADC)	2,385	2,364	2,376	2,382	2,401	2,430	2,419	2,423
Total of IBNR Liabilities Net of Impact of ADC	2
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	2,418	2,362	2,352	2,329	2,293	2,207	2,073	1,869	1,545	795
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	21
Paid Impact of ADC	(20)
U.S. Property and Special Risks | 2014 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(52)	(76)	(70)	(78)	(76)	(64)	(61)	(67)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	24
U.S. Property and Special Risks | 2015
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,493	2,490	2,479	2,471	2,466	2,492	2,489	2,506	2,567
2023 Prior Year Development Excluding the Impact of ADC	3
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 4
Cumulative Number of Reported Claims | country	59,513
Incurred Impact of ADC	$ (100)
IBNR Impact of ADC	(1)
2023 (Net of Impact of ADC)	2,393	2,375	2,372	2,372	2,372	2,405	2,391	2,365
Total of IBNR Liabilities Net of Impact of ADC	3
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	2,457	2,391	2,344	2,308	2,240	2,121	1,878	1,572	844
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	18
Paid Impact of ADC	(67)
U.S. Property and Special Risks | 2015 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(100)	(115)	(107)	(99)	(94)	(87)	(98)	(141)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	15
U.S. Property and Special Risks | 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,713	2,700	2,694	2,707	2,697	2,690	2,748	2,674
2023 Prior Year Development Excluding the Impact of ADC	13
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 8
Cumulative Number of Reported Claims | country	54,821
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	2,713	2,700	2,694	2,707	2,697	2,690	2,748	2,674
Total of IBNR Liabilities Net of Impact of ADC	8
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	2,647	2,616	2,539	2,464	2,296	2,076	1,747	821
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	13
Paid Impact of ADC	0
U.S. Property and Special Risks | 2016 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Property and Special Risks | 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	4,175	4,212	4,173	4,153	4,127	4,239	4,673
2023 Prior Year Development Excluding the Impact of ADC	(37)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 15
Cumulative Number of Reported Claims | country	79,764
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	4,175	4,212	4,173	4,153	4,127	4,239	4,673
Total of IBNR Liabilities Net of Impact of ADC	15
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	4,055	3,999	3,897	3,638	3,281	2,625	1,137
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(37)
Paid Impact of ADC	0
U.S. Property and Special Risks | 2017 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Property and Special Risks | 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	3,210	3,201	3,229	2,992	2,993	2,978
2023 Prior Year Development Excluding the Impact of ADC	9
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 112
Cumulative Number of Reported Claims | country	69,922
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	3,210	3,201	3,229	2,992	2,993	2,978
Total of IBNR Liabilities Net of Impact of ADC	112
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	2,994	2,863	2,715	2,509	2,162	977
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	9
Paid Impact of ADC	0
U.S. Property and Special Risks | 2018 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Property and Special Risks | 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,177	2,222	2,211	2,146	2,177
2023 Prior Year Development Excluding the Impact of ADC	(45)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 25
Cumulative Number of Reported Claims | country	78,848
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	2,177	2,222	2,211	2,146	2,177
Total of IBNR Liabilities Net of Impact of ADC	25
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	2,083	2,037	1,906	1,673	1,039
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(45)
Paid Impact of ADC	0
U.S. Property and Special Risks | 2019 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Property and Special Risks | 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	3,238	3,280	3,320	3,391
2023 Prior Year Development Excluding the Impact of ADC	(42)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 761
Cumulative Number of Reported Claims | country	68,644
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	3,238	3,280	3,320	3,391
Total of IBNR Liabilities Net of Impact of ADC	761
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	2,190	1,874	1,613	844
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(42)
Paid Impact of ADC	0
U.S. Property and Special Risks | 2020 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Property and Special Risks | 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,160	2,213	2,339
2023 Prior Year Development Excluding the Impact of ADC	(53)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 101
Cumulative Number of Reported Claims | country	81,795
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	2,160	2,213	2,339
Total of IBNR Liabilities Net of Impact of ADC	101
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,983	1,743	878
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(53)
Paid Impact of ADC	0
U.S. Property and Special Risks | 2021 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Property and Special Risks | 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	3,281	3,171
2023 Prior Year Development Excluding the Impact of ADC	110
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 690
Cumulative Number of Reported Claims | country	85,477
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	3,281	3,171
Total of IBNR Liabilities Net of Impact of ADC	690
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	2,207	1,208
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	110
Paid Impact of ADC	0
U.S. Property and Special Risks | 2022 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Property and Special Risks | 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,528
2023 Prior Year Development Excluding the Impact of ADC
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 777
Cumulative Number of Reported Claims | country	88,129
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	2,528
Total of IBNR Liabilities Net of Impact of ADC	777
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,173
Prior Year Development Net of External Reinsurance After ADC Cessions(a)
Paid Impact of ADC	0
U.S. Property and Special Risks | 2023 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Property and Special Risks | Short Duration Insurance Contracts Last Ten Accident Years
Liability for Claims and Claims Adjustment Expense [Line Items]
2023 Prior Year Development Excluding the Impact of ADC	(45)
Incurred Impact of ADC	(152)
2023 (Net of Impact of ADC)	28,260	25,738	22,714	20,143	16,767	14,742	12,231	7,462
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(6)
U.S. Property and Special Risks | Short Duration Insurance Contracts Last Ten Accident Years | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(152)	(191)	(177)	(177)	(170)	(151)	(159)	(208)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	39
U.S. Property and Special Risks | Shortduration Insurance Contracts Accident Years Prior To Current Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	0
U.S. Property and Special Risks | Incurred Impact Of Adverse Development Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	87
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(146)
U.S. Property and Special Risks | Short Duration Insurance Contracts Accident Years Prior To2012
Liability for Claims and Claims Adjustment Expense [Line Items]
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	39
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	9
U.S. Property and Special Risks | Short Duration Insurance Contracts Accident Years Prior To2012 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(30)
U.S. Property and Special Risks | Net Of Impact Of Adverse Development Reinsurance Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	(24,120)
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	263
Unallocated loss adjustment expense prior year development	(3)
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	4,403
U.S. Property and Special Risks | Unallocated To Accident Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Unallocated loss adjustment expense prior year development	(4)
U.S. Personal Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	12,876
2023 Prior Year Development Excluding the Impact of ADC	(64)
Incurred Impact of ADC	(1)
2023 (Net of Impact of ADC)	12,860
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	12,060
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(48)
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	768
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(65)
Paid Impact of ADC	$ (16)
Year 1 (as a percent)	61.60%
Year 2 (as a percent)	23.80%
Year 3 (as a percent)	5.20%
Year 4 (as a percent)	0.80%
Year 5 (as a percent)	2.40%
Year 6 (as a percent)	0.90%
Year 7 (as a percent)	0.50%
Year 8 (as a percent)	0.30%
Year 9 (as a percent)	0.30%
Year 10 (as a percent)	0.30%
U.S. Personal Insurance | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 16
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(1)
Unallocated loss adjustment expense prior year development	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(1)
U.S. Personal Insurance | 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,592	1,592	1,587	1,588	1,584	1,583	1,572	1,572	1,562	1,552
2023 Prior Year Development Excluding the Impact of ADC	0
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 5
Cumulative Number of Reported Claims | country	275,132
Incurred Impact of ADC	$ (8)
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,584	1,584	1,582	1,584	1,580	1,571	1,564	1,564
Total of IBNR Liabilities Net of Impact of ADC	5
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,584	1,579	1,572	1,568	1,555	1,536	1,507	1,463	1,380	959
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
Paid Impact of ADC	(8)
U.S. Personal Insurance | 2014 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(8)	(8)	(5)	(4)	(4)	(12)	(8)	(8)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Personal Insurance | 2015
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,487	1,488	1,487	1,485	1,482	1,483	1,494	1,498	1,511
2023 Prior Year Development Excluding the Impact of ADC	(1)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 8
Cumulative Number of Reported Claims | country	261,176
Incurred Impact of ADC	$ (8)
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,479	1,481	1,482	1,480	1,476	1,472	1,475	1,476
Total of IBNR Liabilities Net of Impact of ADC	8
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,471	1,468	1,463	1,461	1,455	1,439	1,411	1,320	931
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(2)
Paid Impact of ADC	(8)
U.S. Personal Insurance | 2015 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(8)	(7)	(5)	(5)	(6)	(11)	(19)	(22)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(1)
U.S. Personal Insurance | 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,541	1,544	1,544	1,542	1,540	1,533	1,533	1,536
2023 Prior Year Development Excluding the Impact of ADC	(3)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 12
Cumulative Number of Reported Claims | country	247,479
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,541	1,544	1,544	1,542	1,540	1,533	1,533	1,536
Total of IBNR Liabilities Net of Impact of ADC	12
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,521	1,518	1,512	1,501	1,460	1,422	1,344	857
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(3)
Paid Impact of ADC	0
U.S. Personal Insurance | 2016 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Personal Insurance | 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,896	1,916	1,924	2,057	2,011	2,137	1,878
2023 Prior Year Development Excluding the Impact of ADC	(20)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 15
Cumulative Number of Reported Claims | country	220,038
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,896	1,916	1,924	2,057	2,011	2,137	1,878
Total of IBNR Liabilities Net of Impact of ADC	15
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,861	1,852	1,826	1,789	1,896	1,672	941
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(20)
Paid Impact of ADC	0
U.S. Personal Insurance | 2017 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Personal Insurance | 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,920	1,936	1,937	2,154	2,193	2,188
2023 Prior Year Development Excluding the Impact of ADC	(16)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 33
Cumulative Number of Reported Claims | country	102,256
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,920	1,936	1,937	2,154	2,193	2,188
Total of IBNR Liabilities Net of Impact of ADC	33
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,849	1,832	1,789	1,973	1,939	1,227
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(16)
Paid Impact of ADC	0
U.S. Personal Insurance | 2018 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Personal Insurance | 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,578	1,596	1,646	1,664	1,593
2023 Prior Year Development Excluding the Impact of ADC	(18)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 43
Cumulative Number of Reported Claims | country	93,428
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	1,578	1,596	1,646	1,664	1,593
Total of IBNR Liabilities Net of Impact of ADC	43
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	1,491	1,416	1,379	1,295	884
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(18)
Paid Impact of ADC	0
U.S. Personal Insurance | 2019 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Personal Insurance | 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	894	913	906	954
2023 Prior Year Development Excluding the Impact of ADC	(19)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 51
Cumulative Number of Reported Claims | country	55,101
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	894	913	906	954
Total of IBNR Liabilities Net of Impact of ADC	51
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	824	725	679	667
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(19)
Paid Impact of ADC	0
U.S. Personal Insurance | 2020 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Personal Insurance | 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	762	765	748
2023 Prior Year Development Excluding the Impact of ADC	(3)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 70
Cumulative Number of Reported Claims | country	56,234
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	762	765	748
Total of IBNR Liabilities Net of Impact of ADC	70
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	658	650	488
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(3)
Paid Impact of ADC	0
U.S. Personal Insurance | 2021 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Personal Insurance | 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	529	517
2023 Prior Year Development Excluding the Impact of ADC	12
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 93
Cumulative Number of Reported Claims | country	51,983
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	529	517
Total of IBNR Liabilities Net of Impact of ADC	93
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	401	372
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	12
Paid Impact of ADC	0
U.S. Personal Insurance | 2022 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Personal Insurance | 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	677
2023 Prior Year Development Excluding the Impact of ADC
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 248
Cumulative Number of Reported Claims | country	32,022
Incurred Impact of ADC	$ 0
IBNR Impact of ADC	0
2023 (Net of Impact of ADC)	677
Total of IBNR Liabilities Net of Impact of ADC	248
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	400
Prior Year Development Net of External Reinsurance After ADC Cessions(a)
Paid Impact of ADC	0
U.S. Personal Insurance | 2023 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	0
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Personal Insurance | Short Duration Insurance Contracts Last Ten Accident Years
Liability for Claims and Claims Adjustment Expense [Line Items]
2023 Prior Year Development Excluding the Impact of ADC	(68)
Incurred Impact of ADC	(16)
2023 (Net of Impact of ADC)	12,860	12,252	11,769	11,435	10,393	8,901	6,450	4,576
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(69)
U.S. Personal Insurance | Short Duration Insurance Contracts Last Ten Accident Years | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred Impact of ADC	(16)	(15)	(10)	(9)	(10)	(23)	(27)	(30)
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	(1)
U.S. Personal Insurance | Shortduration Insurance Contracts Accident Years Prior To Current Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	0
U.S. Personal Insurance | Incurred Impact Of Adverse Development Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	16
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(1)
U.S. Personal Insurance | Short Duration Insurance Contracts Accident Years Prior To2012
Liability for Claims and Claims Adjustment Expense [Line Items]
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	4
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	4
U.S. Personal Insurance | Short Duration Insurance Contracts Accident Years Prior To2012 | Adverse Development Reinsurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	0
U.S. Personal Insurance | Net Of Impact Of Adverse Development Reinsurance Cover
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	(12,044)
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(49)
Unallocated loss adjustment expense prior year development	0
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	767
U.S. Personal Insurance | Unallocated To Accident Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Unallocated loss adjustment expense prior year development	0
UK/Europe Casualty and Financial lines
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	13,695
2023 Prior Year Development Excluding the Impact of ADC	165
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	7,109
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	861
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	7,447
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	$ 165
Year 1 (as a percent)	5.60%
Year 2 (as a percent)	14.30%
Year 3 (as a percent)	12.20%
Year 4 (as a percent)	11.30%
Year 5 (as a percent)	9.30%
Year 6 (as a percent)	10.30%
Year 7 (as a percent)	6.10%
Year 8 (as a percent)	4.90%
Year 9 (as a percent)	3.70%
Year 10 (as a percent)	2.10%
UK/Europe Casualty and Financial lines | 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	$ 1,117	1,111	1,106	1,064	1,122	1,034	1,039	1,032	1,009	1,036
2023 Prior Year Development Excluding the Impact of ADC	6
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 75
Cumulative Number of Reported Claims | country	102,063
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 883	859	818	757	695	629	529	409	258	72
UK/Europe Casualty and Financial lines | 2015
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,266	1,258	1,238	1,234	1,244	1,170	1,262	1,233	1,092
2023 Prior Year Development Excluding the Impact of ADC	8
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 74
Cumulative Number of Reported Claims | country	113,865
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,041	994	949	859	683	568	433	240	71
UK/Europe Casualty and Financial lines | 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,613	1,610	1,597	1,601	1,498	1,497	1,453	1,314
2023 Prior Year Development Excluding the Impact of ADC	3
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 100
Cumulative Number of Reported Claims | country	142,721
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,260	1,168	1,059	930	775	586	379	119
UK/Europe Casualty and Financial lines | 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,408	1,366	1,381	1,321	1,252	1,323	1,343
2023 Prior Year Development Excluding the Impact of ADC	42
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 177
Cumulative Number of Reported Claims | country	149,665
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 964	896	753	602	447	280	96
UK/Europe Casualty and Financial lines | 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,664	1,619	1,521	1,482	1,415	1,343
2023 Prior Year Development Excluding the Impact of ADC	45
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 245
Cumulative Number of Reported Claims | country	151,467
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,128	903	742	572	374	113
UK/Europe Casualty and Financial lines | 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,345	1,351	1,334	1,262	1,005
2023 Prior Year Development Excluding the Impact of ADC	(6)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 292
Cumulative Number of Reported Claims | country	142,426
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 760	658	478	310	98
UK/Europe Casualty and Financial lines | 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,202	1,216	1,271	1,219
2023 Prior Year Development Excluding the Impact of ADC	(14)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 474
Cumulative Number of Reported Claims | country	85,762
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 507	367	228	60
UK/Europe Casualty and Financial lines | 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,347	1,335	1,375
2023 Prior Year Development Excluding the Impact of ADC	12
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 723
Cumulative Number of Reported Claims | country	76,503
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 345	233	51
UK/Europe Casualty and Financial lines | 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,261	1,300
2023 Prior Year Development Excluding the Impact of ADC	(39)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 894
Cumulative Number of Reported Claims | country	71,630
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 185	57
UK/Europe Casualty and Financial lines | 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,472
2023 Prior Year Development Excluding the Impact of ADC
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 1,100
Cumulative Number of Reported Claims | country	57,306
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 36
UK/Europe Casualty and Financial lines | Short Duration Insurance Contracts Last Ten Accident Years
Liability for Claims and Claims Adjustment Expense [Line Items]
2023 Prior Year Development Excluding the Impact of ADC	57
UK/Europe Casualty and Financial lines | Shortduration Insurance Contracts Accident Years Prior To Current Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	0
UK/Europe Casualty and Financial lines | Short Duration Insurance Contracts Accident Years Prior To2012
Liability for Claims and Claims Adjustment Expense [Line Items]
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	108
UK/Europe Casualty and Financial lines | Unallocated To Accident Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Unallocated loss adjustment expense prior year development	0
UK/Europe Property and Special Risks
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	13,306
2023 Prior Year Development Excluding the Impact of ADC	81
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	10,479
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	86
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	2,913
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	$ 81
Year 1 (as a percent)	21.10%
Year 2 (as a percent)	38.70%
Year 3 (as a percent)	16.70%
Year 4 (as a percent)	7.70%
Year 5 (as a percent)	2.70%
Year 6 (as a percent)	2.10%
Year 7 (as a percent)	0.80%
Year 8 (as a percent)	0.20%
Year 9 (as a percent)	0.30%
Year 10 (as a percent)	0.30%
UK/Europe Property and Special Risks | 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	$ 1,349	1,360	1,382	1,387	1,426	1,450	1,460	1,431	1,470	1,439
2023 Prior Year Development Excluding the Impact of ADC	(11)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ (2)
Cumulative Number of Reported Claims | country	48,030
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,354	1,350	1,342	1,329	1,320	1,293	1,255	1,187	912	311
UK/Europe Property and Special Risks | 2015
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,442	1,455	1,421	1,434	1,444	1,463	1,531	1,469	1,552
2023 Prior Year Development Excluding the Impact of ADC	(13)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 7
Cumulative Number of Reported Claims | country	54,639
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,362	1,363	1,362	1,354	1,331	1,295	1,193	920	346
UK/Europe Property and Special Risks | 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,604	1,609	1,674	1,678	1,682	1,678	1,685	1,536
2023 Prior Year Development Excluding the Impact of ADC	(5)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 10
Cumulative Number of Reported Claims | country	57,287
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,585	1,591	1,574	1,545	1,500	1,367	1,114	456
UK/Europe Property and Special Risks | 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,565	1,566	1,600	1,616	1,609	1,614	1,649
2023 Prior Year Development Excluding the Impact of ADC	(1)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 12
Cumulative Number of Reported Claims | country	53,411
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,472	1,459	1,420	1,364	1,222	940	353
UK/Europe Property and Special Risks | 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,463	1,468	1,520	1,533	1,555	1,505
2023 Prior Year Development Excluding the Impact of ADC	(5)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 8
Cumulative Number of Reported Claims | country	44,183
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,339	1,303	1,289	1,161	978	316
UK/Europe Property and Special Risks | 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,086	1,090	1,101	1,100	1,138
2023 Prior Year Development Excluding the Impact of ADC	(4)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 39
Cumulative Number of Reported Claims | country	33,637
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 944	907	820	649	264
UK/Europe Property and Special Risks | 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,218	1,200	1,241	1,301
2023 Prior Year Development Excluding the Impact of ADC	18
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 136
Cumulative Number of Reported Claims | country	25,822
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 912	819	668	249
UK/Europe Property and Special Risks | 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	932	982	1,019
2023 Prior Year Development Excluding the Impact of ADC	(50)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 64
Cumulative Number of Reported Claims | country	22,306
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 691	504	189
UK/Europe Property and Special Risks | 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,288	1,123
2023 Prior Year Development Excluding the Impact of ADC	165
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 220
Cumulative Number of Reported Claims | country	23,295
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 661	194
UK/Europe Property and Special Risks | 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,359
2023 Prior Year Development Excluding the Impact of ADC
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 539
Cumulative Number of Reported Claims | country	15,946
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 159
UK/Europe Property and Special Risks | Short Duration Insurance Contracts Last Ten Accident Years
Liability for Claims and Claims Adjustment Expense [Line Items]
2023 Prior Year Development Excluding the Impact of ADC	94
UK/Europe Property and Special Risks | Shortduration Insurance Contracts Accident Years Prior To Current Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	0
UK/Europe Property and Special Risks | Short Duration Insurance Contracts Accident Years Prior To2012
Liability for Claims and Claims Adjustment Expense [Line Items]
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	(13)
UK/Europe Property and Special Risks | Unallocated To Accident Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Unallocated loss adjustment expense prior year development	0
UK/Europe and Japan Personal Insurance
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	20,193
2023 Prior Year Development Excluding the Impact of ADC	(57)
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	18,747
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	37
Liabilities for losses and loss adjustment expenses and prior year loss development, net of reinsurance	1,483
Prior Year Development Net of External Reinsurance After ADC Cessions(a)	$ (57)
Year 1 (as a percent)	57.90%
Year 2 (as a percent)	26.20%
Year 3 (as a percent)	7.20%
Year 4 (as a percent)	3.60%
Year 5 (as a percent)	1.80%
Year 6 (as a percent)	1.30%
Year 7 (as a percent)	0.50%
Year 8 (as a percent)	0.40%
Year 9 (as a percent)	0.30%
Year 10 (as a percent)	0.20%
UK/Europe and Japan Personal Insurance | 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	$ 2,224	2,220	2,197	2,199	2,197	2,197	2,204	2,207	2,220	2,210
2023 Prior Year Development Excluding the Impact of ADC	4
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 2
Cumulative Number of Reported Claims | country	1,799,271
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 2,189	2,184	2,179	2,170	2,158	2,137	2,090	1,999	1,817	$ 1,198
UK/Europe and Japan Personal Insurance | 2015
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,257	2,254	2,256	2,255	2,255	2,257	2,265	2,264	2,284
2023 Prior Year Development Excluding the Impact of ADC	3
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 0
Cumulative Number of Reported Claims | country	1,777,699
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 2,244	2,234	2,226	2,209	2,183	2,146	2,046	1,861	$ 1,228
UK/Europe and Japan Personal Insurance | 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,212	2,209	2,216	2,219	2,221	2,226	2,240	2,241
2023 Prior Year Development Excluding the Impact of ADC	3
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 1
Cumulative Number of Reported Claims | country	1,794,987
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 2,195	2,187	2,173	2,147	2,102	2,013	1,830	$ 1,225
UK/Europe and Japan Personal Insurance | 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,108	2,100	2,115	2,099	2,103	2,118	2,196
2023 Prior Year Development Excluding the Impact of ADC	8
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 0
Cumulative Number of Reported Claims | country	1,718,502
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 2,077	2,078	2,056	2,020	1,950	1,791	$ 1,200
UK/Europe and Japan Personal Insurance | 2018
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,448	2,450	2,431	2,458	2,461	2,555
2023 Prior Year Development Excluding the Impact of ADC	(2)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 4
Cumulative Number of Reported Claims | country	1,915,683
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 2,404	2,352	2,309	2,225	2,063	$ 1,520
UK/Europe and Japan Personal Insurance | 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	2,002	2,000	2,015	2,050	2,085
2023 Prior Year Development Excluding the Impact of ADC	2
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 3
Cumulative Number of Reported Claims | country	1,673,976
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,950	1,916	1,854	1,726	$ 1,219
UK/Europe and Japan Personal Insurance | 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,701	1,713	1,771	1,909
2023 Prior Year Development Excluding the Impact of ADC	(12)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 19
Cumulative Number of Reported Claims | country	1,389,704
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,619	1,576	1,470	$ 1,020
UK/Europe and Japan Personal Insurance | 2021
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,689	1,719	1,776
2023 Prior Year Development Excluding the Impact of ADC	(30)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 32
Cumulative Number of Reported Claims | country	1,387,230
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,533	1,423	$ 1,003
UK/Europe and Japan Personal Insurance | 2022
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,854	1,889
2023 Prior Year Development Excluding the Impact of ADC	(35)
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 89
Cumulative Number of Reported Claims | country	2,050,657
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 1,572	$ 1,100
UK/Europe and Japan Personal Insurance | 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Incurred losses and allocated loss adjustment expenses, undiscounted and net of reinsurance	1,698
2023 Prior Year Development Excluding the Impact of ADC
Total of IBNR Liabilities Plus Expected Development on Reported Losses	$ 256
Cumulative Number of Reported Claims | country	1,275,686
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	$ 964
UK/Europe and Japan Personal Insurance | Short Duration Insurance Contracts Last Ten Accident Years
Liability for Claims and Claims Adjustment Expense [Line Items]
2023 Prior Year Development Excluding the Impact of ADC	(59)
UK/Europe and Japan Personal Insurance | Shortduration Insurance Contracts Accident Years Prior To Current Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance from the table below	0
UK/Europe and Japan Personal Insurance | Short Duration Insurance Contracts Accident Years Prior To2012
Liability for Claims and Claims Adjustment Expense [Line Items]
Liabilities for losses and loss adjustment expenses and prior year development before accident year 2014, net of reinsurance	2
UK/Europe and Japan Personal Insurance | Unallocated To Accident Year
Liability for Claims and Claims Adjustment Expense [Line Items]
Unallocated loss adjustment expense prior year development	$ 0