Claim and Claim Adjustment Expense Reserves - General Liability (Details) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($) Claim	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2016	$ 4,685	$ 4,096	$ 3,679
Total net liability for unpaid claim and claim adjustment expenses	20,617	19,263	18,163	$ 16,929
General liability
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	9,151
IBNR	3,410
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	4,576
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented	4,575
Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2016	179
Liability for unallocated claim adjustment expenses for accident years presented	83
Total net liability for unpaid claim and claim adjustment expenses	4,837
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	114	75	149
Total net development for the accident years presented above	130	48	134
Total net development for accident years prior to 2016	(30)	27	15
Total unallocated claim adjustment expense development	14	0	0
General liability | Short-duration Insurance Contracts, Accident Year 2016
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	723	712	704	684	$ 683	$ 673	$ 671	$ 667	$ 659	$ 623
IBNR	$ 23
Cumulative number of claims | Claim	24,982
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 681	652	620	582	524	481	407	279	163	$ 32
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	11	8	20	1	10	2	4	8	36
IBNR, Total	100
General liability | Short-duration Insurance Contracts, Accident Year 2017
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	749	713	690	652	630	634	632	632	632
IBNR	$ 15
Cumulative number of claims | Claim	22,611
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 705	657	606	553	471	399	250	118	$ 23
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	36	23	38	22	(4)	2	0	0
IBNR, Total	117
General liability | Short-duration Insurance Contracts, Accident Year 2018
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	663	665	679	650	639	646	644	653
IBNR	$ 63
Cumulative number of claims | Claim	20,631
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 573	546	491	428	307	228	107	$ 33
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	(2)	(14)	29	11	(7)	2	(9)
IBNR, Total	10
General liability | Short-Duration Insurance Contract, Accident Year 2019
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	747	727	720	691	682	682	680
IBNR	$ 98
Cumulative number of claims | Claim	20,091
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 607	532	455	322	181	98	$ 25
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	20	7	29	9	0	2
IBNR, Total	67
General liability | Short-Duration Insurance Contract, Accident Year 2020
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	662	702	736	726	722	723
IBNR	$ 139
Cumulative number of claims | Claim	15,152
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 450	367	280	192	99	$ 23
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	(40)	(34)	10	4	(1)
IBNR, Total	(61)
General liability | Short-Duration Insurance Contract, Accident Year 2021
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	833	814	793	784	782
IBNR	$ 189
Cumulative number of claims | Claim	16,349
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 542	391	262	140	$ 26
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	19	21	9	2
IBNR, Total	51
General liability | Short-Duration Insurance Contract, Accident Year 2022
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	952	930	928	929
IBNR	$ 316
Cumulative number of claims | Claim	18,494
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 439	260	123	$ 29
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	22	2	(1)
IBNR, Total	23
General liability | Short-Duration Insurance Contract, Accident Year 2023
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	1,146	1,106	1,071
IBNR	$ 516
Cumulative number of claims | Claim	18,905
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 356	153	$ 33
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	40	35
IBNR, Total	75
General liability | Short-Duration Insurance Contract, Accident Year 2024
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	1,295	1,271
IBNR	$ 833
Cumulative number of claims | Claim	20,250
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 180	$ 34
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	24
IBNR, Total	24
General liability | Short-Duration Insurance Contract, Accident Year 2025
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	1,381
IBNR	$ 1,218
Cumulative number of claims | Claim	15,771
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 43