Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	$ 129,926	$ 122,893
Consumer portfolio segment | Consumer loan
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	87,240	81,821
Consumer portfolio segment | Consumer loan | Performing financial instruments
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	86,497	81,101
Consumer portfolio segment | Consumer loan | Nonperforming financial instruments
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	743	720
Consumer portfolio segment | Automobile loan
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	70,539	68,071
Consumer portfolio segment | Automobile loan | Performing financial instruments
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	69,875	67,468
Consumer portfolio segment | Automobile loan | Nonperforming financial instruments
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	664	603
Consumer portfolio segment | Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	16,701	13,750
Consumer portfolio segment | Residential mortgage | Performing financial instruments
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	16,622	13,633
Consumer portfolio segment | Residential mortgage | Nonperforming financial instruments
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	79	117
Consumer portfolio segment | Mortgage Finance
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	15,155	11,657
Consumer portfolio segment | Mortgage Finance | Performing financial instruments
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	15,146	11,632
Consumer portfolio segment | Mortgage Finance | Nonperforming financial instruments
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	9	25
Consumer portfolio segment | Mortgage - Legacy
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	1,546	2,093
Consumer portfolio segment | Mortgage - Legacy | Performing financial instruments
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	1,476	2,001
Consumer portfolio segment | Mortgage - Legacy | Nonperforming financial instruments
Financing Receivable, Recorded Investment [Line Items]
Finance receivables and loans, net	$ 70	$ 92