Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 245	$ 226	$ 488	$ 447
All other revenue	261	86	516	307
Total other revenue	506	312	1,004	754
Remarketing gains (losses), net	70	50	117	100
Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	36	35	74	67
All other revenue	47	37	86	73
Total other revenue	83	72	160	140
Remarketing gains (losses), net	70	50	117	100
Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	175	167	347	333
All other revenue	162	(9)	371	95
Total other revenue	337	158	718	428
Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
All other revenue	5	4	9	18
Total other revenue	5	4	9	18
Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
All other revenue	28	19	57	43
Total other revenue	28	19	57	43
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	34	24	67	47
All other revenue	19	35	(7)	78
Total other revenue	53	59	60	125
Noninsurance contracts
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	171	163	340	325
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	171	163	340	325
Unearned revenue, remaining performance obligation, amount	3,000	3,000	3,000	3,000	$ 3,000	$ 3,000	$ 3,000	$ 3,100
Unearned revenue, revenue recognized	243	234	484	465
Capitalized contract cost, net	1,800	1,800	1,800	1,800	$ 1,800	$ 1,800	$ 1,800	$ 1,900
Capitalized contract cost, amortization	144	140	288	277
Noninsurance contracts | Insurance operations | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-07-01
Disaggregation of Revenue [Line Items]
Unearned revenue, remaining performance obligation, amount	$ 464		$ 464
Remaining performance obligation, expected timing of satisfaction, period	6 months		6 months
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	$ 812		$ 812
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	$ 644		$ 644
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	$ 467		$ 467
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]: 2027-01-01
Disaggregation of Revenue [Line Items]
Unearned revenue, remaining performance obligation, amount	$ 582		$ 582
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	31	29	64	56
Remarketing fee income | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	31	29	64	56
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	23	13	46	24
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	23	13	46	24
Banking fees and interchange income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	10	21	21
Customer rewards expense	5	3	9	6
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	10	21	21
Brokered/agent commissions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	4	7	8
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	4	4	7	8
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	5	7	10	13
Product and Service, Other | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5	6	10	11
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	$ 0	$ 1	$ 0	$ 2