Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	$ 128,609	$ 129,926	$ 126,605
Consumer portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	90,081	87,240
Consumer portfolio segment | Performing Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	89,331	86,497
Consumer portfolio segment | Nonperforming Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	750	743
Consumer portfolio segment | Automotive loan
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	73,071	70,539	69,995
Consumer portfolio segment | Automotive loan | Performing Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	72,379	69,875
Consumer portfolio segment | Automotive loan | Nonperforming Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	692	664
Consumer portfolio segment | Real estate-backed loan
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	17,010	16,701	$ 16,506
Consumer portfolio segment | Real estate-backed loan | Performing Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	16,952	16,622
Consumer portfolio segment | Real estate-backed loan | Nonperforming Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	58	79
Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	15,782	15,155
Consumer portfolio segment | Mortgage Finance operations | Performing Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	15,767	15,146
Consumer portfolio segment | Mortgage Finance operations | Nonperforming Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	15	9
Consumer portfolio segment | Mortgage - Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	1,228	1,546
Consumer portfolio segment | Mortgage - Legacy | Performing Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	1,185	1,476
Consumer portfolio segment | Mortgage - Legacy | Nonperforming Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	$ 43	$ 70