Finance Receivables and Loans, Net (Troubled Debt Restructurings) (Details) $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Financing Receivable, Troubled Debt Restructuring
Financing receivable, modifications, gross carrying value	$ 1,100		$ 867
Loans and leases receivable, impaired, commitment to lend	$ 10		$ 17
Financing receivable, modifications, number of loans	22,843	7,454,000,000
Financing receivable, modifications, pre-modification gross carrying value	$ 355	$ 173
Financing receivable, modifications, post-modification gross carrying value	$ 333	$ 155
Consumer portfolio segment
Financing Receivable, Troubled Debt Restructuring
Financing receivable, modifications, number of loans	22,842	7,448,000,000
Financing receivable, modifications, pre-modification gross carrying value	$ 348	$ 132
Financing receivable, modifications, post-modification gross carrying value	$ 326	$ 114
Consumer portfolio segment \| Automotive loan
Financing Receivable, Troubled Debt Restructuring
Financing receivable, modifications, number of loans	22,800	7,427,000,000
Financing receivable, modifications, pre-modification gross carrying value	$ 340	$ 129
Financing receivable, modifications, post-modification gross carrying value	$ 318	$ 111
Loans modified as a result of COVID-19	16,767
Pre and post modification amount of loans modified as a result of COVID-19	$ 238
Consumer portfolio segment \| Real estate-backed loan
Financing Receivable, Troubled Debt Restructuring
Financing receivable, modifications, number of loans	42	21,000,000
Financing receivable, modifications, pre-modification gross carrying value	$ 8	$ 3
Financing receivable, modifications, post-modification gross carrying value	$ 8	$ 3
Consumer portfolio segment \| Mortgage Finance operations
Financing Receivable, Troubled Debt Restructuring
Financing receivable, modifications, number of loans	10	1,000,000
Financing receivable, modifications, pre-modification gross carrying value	$ 4	$ 0
Financing receivable, modifications, post-modification gross carrying value	$ 4	$ 0
Loans modified as a result of COVID-19	8
Pre and post modification amount of loans modified as a result of COVID-19	$ 3
Consumer portfolio segment \| Mortgage - Legacy
Financing Receivable, Troubled Debt Restructuring
Financing receivable, modifications, number of loans	32	20,000,000
Financing receivable, modifications, pre-modification gross carrying value	$ 4	$ 3
Financing receivable, modifications, post-modification gross carrying value	$ 4	$ 3
Loans modified as a result of COVID-19	15
Pre and post modification amount of loans modified as a result of COVID-19	$ 2
Commercial portfolio segment
Financing Receivable, Troubled Debt Restructuring
Financing receivable, modifications, number of loans	1	6,000,000
Financing receivable, modifications, pre-modification gross carrying value	$ 7	$ 41
Financing receivable, modifications, post-modification gross carrying value	$ 7	$ 41
Commercial portfolio segment \| Automotive loan
Financing Receivable, Troubled Debt Restructuring
Financing receivable, modifications, number of loans	1	6,000,000
Financing receivable, modifications, pre-modification gross carrying value	$ 7	$ 41
Financing receivable, modifications, post-modification gross carrying value	$ 7	$ 41

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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