Finance Receivables and Loans, Net (Schedule of Financing Receivables, Non Accrual Status) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	$ 903	$ 792
Consumer portfolio segment | Consumer loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	719	720
Consumer portfolio segment | Automobile loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	620	603
Consumer portfolio segment | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	99	117
Consumer portfolio segment | Mortgage Finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	18	25
Consumer portfolio segment | Mortgage - Legacy
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	81	92
Commercial portfolio segment | Commercial loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	184	72
Commercial portfolio segment | Commercial and industrial automotive
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	78	27
Commercial portfolio segment | Commercial and industrial other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	99	44
Commercial portfolio segment | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, recorded investment, nonaccrual status	$ 7	$ 1