Finance Receivables and Loans, Net (Schedule of Purchases of Financing Receivables and Loans) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables and loans, significant purchases	$ 2,008	$ 1,266	$ 4,556	$ 3,081
Consumer portfolio segment | Automobile loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables and loans, significant purchases	251	83	652	762
Consumer portfolio segment | Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables and loans, significant purchases	1,743	1,183	3,890	2,319
Commercial portfolio segment | Commercial loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables and loans, significant purchases	$ 14	$ 0	$ 14	$ 0