Reserves for Insurance Losses and Loss Adjustment Expenses - Schedule of Short-duration Insurance Contracts, Claims Development (Details) $ in Millions	Dec. 31, 2024 USD ($) claim	Dec. 31, 2023 USD ($)	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 ($)	Dec. 31, 2015 USD ($)
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	$ 3,230
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	3,112
All outstanding liabilities for loss and allocated loss adjustment expenses before 2015, net of reinsurance	8
Reserves for insurance losses and allocated loss adjustment expenses, net of reinsurance	126	$ 71	$ 44
2015
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	272	272	272	$ 272	$ 272	$ 272	$ 272	$ 272	$ 271	$ 274
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	342,280
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 272	272	272	272	272	272	272	272	272	$ 252
2016
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	328	328	328	328	328	328	328	327	326
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	476,057
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 328	328	328	328	328	328	328	327	$ 302
2017
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	315	315	315	315	315	315	314	310
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	481,750
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 315	315	315	315	315	315	315	$ 289
2018
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	273	272	273	273	272	272	271
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	506,454
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 273	272	273	273	273	273	$ 245
2019
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	305	305	305	305	306	303
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	542,361
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 305	305	305	305	306	$ 278
2020
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	340	339	339	339	343
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	494,524
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 340	340	339	339	$ 313
2021
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	237	237	237	243
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	493,714
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 237	237	236	$ 213
2022
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	269	267	258
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	513,434
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 265	260	$ 225
2023
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	403	385
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 7
Cumulative number of reported claims | claim	602,714
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 387	$ 328
2024
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	488
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 78
Cumulative number of reported claims | claim	621,826
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 390