Claim and Claim Adjustment Expense Reserves - Surety (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
Surety
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	984
IBNR	456
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	492
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented	492
Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2016	13
Liability for unallocated claim adjustment expenses for accident years presented	16
Total net liability for unpaid claim and claim adjustment expenses	521
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	(50)	(68)	(43)
Total net development for the accident years presented above	(40)	(63)	(54)
Total net development for accident years prior to 2016	(7)	(5)	11
Total unallocated claim adjustment expense development	(3)	0	0
Surety | Short-duration Insurance Contracts, Accident Year 2016
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	43	43	43	58	$ 64	$ 67	$ 84	$ 109	$ 124	$ 124
IBNR	$ 3
Cumulative number of claims | Claim	5,590
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 40	40	40	41	43	43	45	45	37	$ 5
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	0	0	(15)	(6)	(3)	(17)	(25)	(15)	0
IBNR, Total	(81)
Surety | Short-duration Insurance Contracts, Accident Year 2017
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	66	67	67	66	71	84	103	115	120
IBNR	$ 3
Cumulative number of claims | Claim	5,928
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 63	63	62	62	49	46	41	37	$ 23
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	(1)	0	1	(5)	(13)	(19)	(12)	(5)
IBNR, Total	(54)
Surety | Short-duration Insurance Contracts, Accident Year 2018
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	58	49	51	56	62	91	108	114
IBNR	$ 2
Cumulative number of claims | Claim	6,322
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 46	41	41	40	39	34	25	$ 5
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	9	(2)	(5)	(6)	(29)	(17)	(6)
IBNR, Total	(56)
Surety | Short-Duration Insurance Contract, Accident Year 2019
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	81	82	82	87	98	112	119
IBNR	$ 6
Cumulative number of claims | Claim	6,286
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 75	74	70	59	44	34	$ 12
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	(1)	0	(5)	(11)	(14)	(7)
IBNR, Total	(38)
Surety | Short-Duration Insurance Contract, Accident Year 2020
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	67	57	67	81	119	128
IBNR	$ 6
Cumulative number of claims | Claim	4,918
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 57	44	33	28	20	$ 4
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	10	(10)	(14)	(38)	(9)
IBNR, Total	(61)
Surety | Short-Duration Insurance Contract, Accident Year 2021
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	74	91	110	129	137
IBNR	$ 12
Cumulative number of claims | Claim	5,003
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 59	42	35	20	$ 5
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	(17)	(19)	(19)	(8)
IBNR, Total	(63)
Surety | Short-Duration Insurance Contract, Accident Year 2022
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	118	132	158	155
IBNR	$ 53
Cumulative number of claims | Claim	5,131
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 59	52	35	$ 12
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	(14)	(26)	3
IBNR, Total	(37)
Surety | Short-Duration Insurance Contract, Accident Year 2023
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	147	169	175
IBNR	$ 92
Cumulative number of claims | Claim	4,889
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 52	27	$ 8
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	(22)	(6)
IBNR, Total	(28)
Surety | Short-Duration Insurance Contract, Accident Year 2024
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	167	171
IBNR	$ 124
Cumulative number of claims | Claim	4,397
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 37	$ 20
Net Strengthening (Releases) of Prior Accident Year Reserves
Total	(4)
IBNR, Total	(4)
Surety | Short-Duration Insurance Contract, Accident Year 2025
Cumulative Net Incurred Claim and Allocated Claim Adjustment Expenses
Total	163
IBNR	$ 155
Cumulative number of claims | Claim	3,143
Cumulative Net Paid Claim and Allocated Claim Adjustment Expenses
Total	$ 4