Reserves for Insurance Losses and Loss Adjustment Expenses (Short-duration Insurance Contracts, Claims Development) (Details) $ in Millions	Dec. 31, 2021 USD ($) claim	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	$ 3,252
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	3,222
All outstanding liabilities for loss and allocated loss adjustment expenses before 2012, net of reinsurance	9
Reserves for insurance losses and allocated loss adjustment expenses, net of reinsurance	39	$ 37	$ 32
Short-duration Insurance Contracts, Accident Year 2012
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	421	421	421	$ 422	$ 422	$ 423	$ 423	$ 423	$ 430	$ 435
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	772,560
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 421	421	421	421	421	419	418	416	412	$ 391
Short-duration Insurance Contracts, Accident Year 2013
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	368	368	368	368	369	370	370	365	376
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	672,279
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 368	368	368	368	368	368	366	364	$ 347
Short-duration Insurance Contracts, Accident Year 2014
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	388	388	388	388	388	388	389	390
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	525,298
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 388	388	388	388	388	388	388	$ 369
Short-duration Insurance Contracts, Accident Year 2015
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	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	$ 252
Short-duration Insurance Contracts, Accident Year 2016
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	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	476,056
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 328	328	328	328	327	$ 302
Short-duration Insurance Contracts, Accident Year 2017
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	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	481,742
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 315	315	315	315	$ 289
Short-duration Insurance Contracts, Accident Year 2018
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	273	272	272	271
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	506,423
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 273	273	273	$ 245
Short-Duration Insurance Contract, Accident Year 2019
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	305	306	303
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	541,936
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 305	306	$ 278
Short-Duration Insurance Contract, Accident Year 2020
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	339	343
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 1
Cumulative number of reported claims | claim	493,097
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 339	$ 313
Short-Duration Insurance Contract, Accident Year 2021
Claims Development [Line Items]
Incurred claims and allocated loss adjustment expenses, net of reinsurance	243
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 24
Cumulative number of reported claims | claim	471,444
Cumulative paid claims and allocated loss adjustment expenses, net of reinsurance	$ 213