Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Jan. 01, 2023	Dec. 31, 2022	Jan. 01, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 243	$ 221
All other revenue	255	221
Total other revenue	498	442
Remarketing gains (losses), net	47	50
Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	38	32
All other revenue	39	36
Total other revenue	77	68
Remarketing gains (losses), net	47	50
Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	172	166
All other revenue	209	104
Total other revenue	381	270
Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
All other revenue	4	14
Total other revenue	4	14
Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
All other revenue	29	24
Total other revenue	29	24
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	33	23
All other revenue	(26)	43
Total other revenue	7	66
Noninsurance contracts
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	169	162
Noninsurance contracts | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Noninsurance contracts | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	169	162
Unearned revenue, remaining performance obligation, amount	3,000	3,000	$ 3,000		$ 3,100
Unearned revenue, revenue recognized	241	231
Capitalized contract cost, net	1,800	1,800		$ 1,800		$ 1,900
Capitalized contract cost, amortization	144	137
Noninsurance contracts | Insurance operations | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-04-01
Disaggregation of Revenue [Line Items]
Unearned revenue, remaining performance obligation, amount	$ 680
Remaining performance obligation, expected timing of satisfaction, period	9 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	$ 779
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	$ 604
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	$ 423
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	$ 481
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
Noninsurance contracts | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Noninsurance contracts | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Remarketing fee income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	33	27
Remarketing fee income | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	33	27
Remarketing fee income | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Remarketing fee income | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Remarketing fee income | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Remarketing fee income | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokerage commissions and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23	11
Brokerage commissions and other revenue | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokerage commissions and other revenue | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokerage commissions and other revenue | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokerage commissions and other revenue | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokerage commissions and other revenue | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23	11
Banking fees and interchange income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10	11
Customer rewards expense	4	3
Banking fees and interchange income | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Banking fees and interchange income | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Banking fees and interchange income | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Banking fees and interchange income | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Banking fees and interchange income | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	10	11
Brokered/agent commissions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	4
Brokered/agent commissions | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokered/agent commissions | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3	4
Brokered/agent commissions | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokered/agent commissions | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokered/agent commissions | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Product and Service, Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5	6
Product and Service, Other | Automotive Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5	5
Product and Service, Other | Insurance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Product and Service, Other | Mortgage Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Product and Service, Other | Corporate Finance operations
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Product and Service, Other | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 1