Revenue from Contracts with Customers (Disaggregation of Revenue) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 221	$ 218
All other revenue	221	347
Total other revenue	442	565
Remarketing gains (losses), net	50	64
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	23	26
All other revenue	43	32
Total other revenue	66	58
Automotive Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	32	33
All other revenue	36	29
Total other revenue	68	62
Remarketing gains (losses), net	50	64
Insurance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	166	159
All other revenue	104	220
Total other revenue	270	379
Mortgage Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
All other revenue	14	40
Total other revenue	14	40
Corporate Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
All other revenue	24	26
Total other revenue	24	26
Noninsurance contracts
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	162	155
Noninsurance contracts | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Noninsurance contracts | Automotive Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Noninsurance contracts | Insurance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	162	155
Unearned revenue, remaining performance obligation, amount	3,000	3,000	$ 3,100	$ 3,000
Unearned revenue, revenue recognized	231	225
Capitalized contract cost, net	1,800	1,800	$ 1,900	$ 1,800
Capitalized contract cost, amortization	137	132
Noninsurance contracts | Insurance operations | Operating Segments | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-04-01
Disaggregation of Revenue [Line Items]
Unearned revenue, remaining performance obligation, amount	$ 648
Remaining performance obligation, expected timing of satisfaction, period	9 months
Noninsurance contracts | Insurance operations | Operating Segments | 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	$ 794
Remaining performance obligation, expected timing of satisfaction, period	1 year
Noninsurance contracts | Insurance operations | Operating Segments | 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	$ 644
Remaining performance obligation, expected timing of satisfaction, period	1 year
Noninsurance contracts | Insurance operations | Operating Segments | 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	$ 448
Remaining performance obligation, expected timing of satisfaction, period	1 year
Noninsurance contracts | Insurance operations | Operating Segments | 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	$ 490
Remaining performance obligation, expected timing of satisfaction, period
Noninsurance contracts | Mortgage Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	0
Noninsurance contracts | Corporate Finance operations | Operating Segments
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	27	27
Remarketing fee income | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Remarketing fee income | Automotive Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	27	27
Remarketing fee income | Insurance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Remarketing fee income | Mortgage Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Remarketing fee income | Corporate Finance operations | Operating Segments
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	11	20
Brokerage commissions and other revenue | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	20
Brokerage commissions and other revenue | Automotive Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokerage commissions and other revenue | Insurance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokerage commissions and other revenue | Mortgage Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokerage commissions and other revenue | Corporate Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Banking fees and interchange income
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	6
Customer rewards expense	3
Banking fees and interchange income | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	11	6
Banking fees and interchange income | Automotive Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Banking fees and interchange income | Insurance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Banking fees and interchange income | Mortgage Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Banking fees and interchange income | Corporate Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokered/agent commissions
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	4
Brokered/agent commissions | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokered/agent commissions | Automotive Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokered/agent commissions | Insurance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4	4
Brokered/agent commissions | Mortgage Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Brokered/agent commissions | Corporate Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6	6
Other | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1	0
Other | Automotive Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5	6
Other | Insurance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Other | Mortgage Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0
Other | Corporate Finance operations | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 0	$ 0