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	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flow Received and Paid to Nonconsolidated Securitization Entities [Line Items]
Cash Flows Between Transferor and Transferee, Purchases of Previously Transferred Financial Assets	$ 1
Cash Flows Between Transferor and Transferee, Servicing Fees	5	$ 9
Cash Flows Between Transferor and Transferee, Beneficial Interest	$ 5
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers		1,138
Cash Flows Between Transferor and Transferee, Receipts on Transferor's Interest in Transferred Financial Assets, Other		$ 2