Revenue from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 228	$ 207	$ 675	$ 640
All other revenue	69	184	376	854
Total other revenue	297	391	1,051	1,494
Remarketing gains (losses), net	39	86	139	278
Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	31	31	98	97
All other revenue	43	30	116	87
Total other revenue	74	61	214	184
Remarketing gains (losses), net	39	86	139	278
Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	167	161	500	482
All other revenue	69	122	164	524
Total other revenue	236	283	664	1,006
Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
All other revenue	7	19	25	81
Total other revenue	7	19	25	81
Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
All other revenue	54	16	97	75
Total other revenue	54	16	97	75
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	30	15	77	61
All other revenue	(104)	(3)	(26)	87
Total other revenue	(74)	12	51	148
Noninsurance contracts
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	164	157	489	470
Noninsurance contracts | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Noninsurance contracts | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	164	157	489	470
Unearned revenue, remaining performance obligation, amount	3,000	3,100	3,000	3,100	$ 3,000	$ 3,100	$ 3,100	$ 3,000
Unearned revenue, revenue recognized	236	228	701	681
Capitalized contract cost, net	1,800	1,900	1,800	1,900	$ 1,800	$ 1,900	$ 1,900	$ 1,800
Capitalized contract cost, amortization	143	135	420	400
Noninsurance contracts | Insurance operations | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Disaggregation of Revenue [Line Items]
Unearned revenue, remaining performance obligation, amount	$ 227		$ 227
Remaining performance obligation, expected timing of satisfaction, period	3 months		3 months
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	$ 853		$ 853
Remaining performance obligation, expected timing of satisfaction, period	1 year		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	$ 715		$ 715
Remaining performance obligation, expected timing of satisfaction, period	1 year		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	$ 527		$ 527
Remaining performance obligation, expected timing of satisfaction, period	1 year		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	$ 682		$ 682
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	0
Noninsurance contracts | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Noninsurance contracts | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Remarketing fee income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	26	26	82	80
Remarketing fee income | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	26	26	82	80
Remarketing fee income | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Remarketing fee income | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Remarketing fee income | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Remarketing fee income | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Brokerage commissions and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	18	12	42	45
Brokerage commissions and other revenue | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Brokerage commissions and other revenue | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Brokerage commissions and other revenue | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Brokerage commissions and other revenue | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Brokerage commissions and other revenue | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	18	12	42	45
Banking fees and interchange income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	2	32	13
Customer rewards expense	4		10
Banking fees and interchange income | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Banking fees and interchange income | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Banking fees and interchange income | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Banking fees and interchange income | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Banking fees and interchange income | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	2	32	13
Brokered/agent commissions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	4	11	12
Brokered/agent commissions | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Brokered/agent commissions | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	4	11	12
Brokered/agent commissions | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Brokered/agent commissions | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Brokered/agent commissions | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Product and Service, Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6	6	19	20
Product and Service, Other | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5	5	16	17
Product and Service, Other | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Product and Service, Other | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Product and Service, Other | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Product and Service, Other | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1	$ 1	$ 3	$ 3