Securitizations and Variable Interest Entities (Schedule of Cash Flow Received from and Paid to Nonconsolidated Securitization Entities) (Details) - Consumer Portfolio Segment [Member] - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Automobile Loan [Member]
Cash Flow Received and Paid to Nonconsolidated Securitization Entities [Line Items]
Cash Flows Between Transferor and Transferee, Purchases of Previously Transferred Financial Assets	$ (2)	$ (491)
Cash Flows Between Transferor and Transferee, Servicing Fees	10	18
Cash Flows Between Transferor and Transferee, Beneficial Interest	9	10
Cash Flow Between Transferee and Transferor Representations And Warranties Obligations	0
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers		1,187
Cash Flows Between Transferor and Transferee, Receipts on Transferor's Interest in Transferred Financial Assets, Other		4
Residential Mortgage [Member]
Cash Flow Received and Paid to Nonconsolidated Securitization Entities [Line Items]
Cash Flows Between Transferor and Transferee, Purchases of Previously Transferred Financial Assets	0	0
Cash Flows Between Transferor and Transferee, Servicing Fees	0	0
Cash Flows Between Transferor and Transferee, Beneficial Interest	0	0
Cash Flow Between Transferee and Transferor Representations And Warranties Obligations	$ 2
Cash Flows Between Transferor and Transferee, Proceeds from New Transfers		0
Cash Flows Between Transferor and Transferee, Receipts on Transferor's Interest in Transferred Financial Assets, Other		$ 0