Securitizations and Variable Interest Entities (Schedule of Cash Flow Received from and Paid to Nonconsolidated Securitization Entities) (Details) - Consumer Portfolio Segment [Member] - Automobile Loan [Member] - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash Flow Received and Paid to Nonconsolidated Securitization Entities [Line Items]
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers	$ 1,187	$ 1,659
Cash Flows Between Transferor and Transferee, Purchases of Previously Transferred Financial Assets	(491)
Cash Flows Between Transferor and Transferee, Servicing Fees	25	27
Cash Flows Between Transferor and Transferee, Beneficial Interest	16
Cash Flows Between Transferor and Transferee, Receipts on Transferor's Interest in Transferred Financial Assets, Other	$ 4	$ 6