Securitizations and Variable Interest Entities (Schedule of Quantitative Information and Net Credit Losses about Securitized and Other Financial Assets Managed Together) (Details) - Consumer Automotive Industry Sector - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together [Line Items]
Loans managed and securitized, principal amount outstanding	$ 1,188		$ 1,188		$ 1,869
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Delinquent Amount at End of Period	11		11		16
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Net Credit Losses During Period	3	$ 2	5	$ 6
Whole Loan Sales
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together [Line Items]
Loans managed and securitized, principal amount outstanding	392		392		634
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Delinquent Amount at End of Period	2		2		3
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Net Credit Losses During Period	1	0	1	1
Variable Interest Entity, Not Primary Beneficiary [Member]
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together [Line Items]
Loans managed and securitized, principal amount outstanding	796		796		1,235
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Delinquent Amount at End of Period	9		9		$ 13
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Net Credit Losses During Period	$ 2	$ 2	$ 4	$ 5