Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	$ 129,210	$ 129,926	$ 125,544
Consumer portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	90,698	87,240
Consumer portfolio segment | Performing Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	89,991	86,497
Consumer portfolio segment | Nonperforming Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	707	743
Consumer portfolio segment | Automotive loan
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	72,898	70,539	70,473
Consumer portfolio segment | Automotive loan | Performing Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	72,256	69,875
Consumer portfolio segment | Automotive loan | Nonperforming Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	642	664
Consumer portfolio segment | Real estate-backed loan
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	17,800	16,701	$ 15,131
Consumer portfolio segment | Real estate-backed loan | Performing Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	17,735	16,622
Consumer portfolio segment | Real estate-backed loan | Nonperforming Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	65	79
Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	16,485	15,155
Consumer portfolio segment | Mortgage Finance operations | Performing Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	16,473	15,146
Consumer portfolio segment | Mortgage Finance operations | Nonperforming Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	12	9
Consumer portfolio segment | Mortgage - Legacy
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	1,315	1,546
Consumer portfolio segment | Mortgage - Legacy | Performing Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	1,262	1,476
Consumer portfolio segment | Mortgage - Legacy | Nonperforming Financial Instruments
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	$ 53	$ 70