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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
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	$ 121		$ 121		$ 624
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Delinquent Amount at End of Period	2		2		8
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Net Credit Losses During Period	0	$ 1	1	$ 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	0		0		207
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Delinquent Amount at End of Period	0		0		2
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Net Credit Losses During Period	0	0	0	1
Off-balance sheet variable interest entities
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	121		121		417
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Delinquent Amount at End of Period	2		2		$ 6
Derecognized Assets, Securitized or Asset-backed Financing Arrangement Assets and any Other Financial Assets Managed Together, Net Credit Losses During Period	$ 0	$ 1	$ 1	$ 5