Revenue from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2022	Jan. 01, 2021	Jan. 01, 2020
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 908	$ 852	$ 753
All other revenue	670	1,187	1,230
Total other revenue	1,578	2,039	1,983
Remarketing gains (losses), net	170	344	127
Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	127	129	88
All other revenue	179	122	116
Total other revenue	306	251	204
Remarketing gains (losses), net	170	344	127
Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	669	643	601
All other revenue	354	702	733
Total other revenue	1,023	1,345	1,334
Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
All other revenue	27	94	102
Total other revenue	27	94	102
Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
All other revenue	122	128	45
Total other revenue	122	128	45
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	112	80	64
All other revenue	(12)	141	234
Total other revenue	100	221	298
Noninsurance contracts
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	655	627	584
Noninsurance contracts | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Noninsurance contracts | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	655	627	584
Unearned revenue, remaining performance obligation, amount	3,000	3,100	3,000	$ 3,100	$ 3,000	$ 2,900
Unearned revenue, revenue recognized	939	909	866
Capitalized contract cost, net	1,800	1,900	1,800
Capitalized contract cost, amortization	564	537	498
Noninsurance contracts | Insurance operations | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Disaggregation of Revenue [Line Items]
Unearned revenue, remaining performance obligation, amount	$ 883
Remaining performance obligation, expected timing of satisfaction, period	1 year
Noninsurance contracts | Insurance operations | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Disaggregation of Revenue [Line Items]
Unearned revenue, remaining performance obligation, amount	$ 747
Remaining performance obligation, expected timing of satisfaction, period	1 year
Noninsurance contracts | Insurance operations | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Disaggregation of Revenue [Line Items]
Unearned revenue, remaining performance obligation, amount	$ 565
Remaining performance obligation, expected timing of satisfaction, period	1 year
Noninsurance contracts | Insurance operations | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Disaggregation of Revenue [Line Items]
Unearned revenue, remaining performance obligation, amount	$ 384
Remaining performance obligation, expected timing of satisfaction, period	1 year
Noninsurance contracts | Insurance operations | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-01-01
Disaggregation of Revenue [Line Items]
Unearned revenue, remaining performance obligation, amount	$ 402
Remaining performance obligation, expected timing of satisfaction, period
Noninsurance contracts | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	0	0
Noninsurance contracts | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Noninsurance contracts | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Remarketing fee income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	107	107	73
Remarketing fee income | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	107	107	73
Remarketing fee income | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Remarketing fee income | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Remarketing fee income | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Remarketing fee income | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Brokerage commissions and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	64	58	52
Brokerage commissions and other revenue | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Brokerage commissions and other revenue | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Brokerage commissions and other revenue | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Brokerage commissions and other revenue | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Brokerage commissions and other revenue | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	64	58	52
Banking fees and interchange income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	44	18	12
Customer rewards expense	14	1
Banking fees and interchange income | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Banking fees and interchange income | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Banking fees and interchange income | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Banking fees and interchange income | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Banking fees and interchange income | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	44	18	12
Brokered/agent commissions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14	16	16
Brokered/agent commissions | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Brokered/agent commissions | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	14	16	16
Brokered/agent commissions | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Brokered/agent commissions | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Brokered/agent commissions | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Product and Service, Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	24	26	16
Product and Service, Other | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20	22	15
Product and Service, Other | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	1
Product and Service, Other | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Product and Service, Other | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0
Product and Service, Other | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 4	$ 4	$ 0