Securitizations and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Variable Interest Entity [Line Items]
Securitization or Asset-backed Financing Arrangement, Financial Asset for which Transfer is Accounted as Sale, Gain (Loss) on Sale	$ 0	$ 0	$ 0	$ 0
Total assets	184,061	$ 180,448	184,061	$ 180,448	$ 180,644
Liabilities	170,235		170,235		166,228
Held-to-maturity securities	1,390		1,390		1,568
Other assets	6,721		6,721		6,073
On-balance sheet variable interest entities
Variable Interest Entity [Line Items]
Total assets	16,622		16,622		19,344
Liabilities	6,499		6,499		9,098
Other assets	893		893		787
On-balance sheet variable interest entities | Consumer Automotive Industry Sector
Variable Interest Entity [Line Items]
Total assets	19,760		19,760		20,376
Liabilities	4,431		4,431		6,070
Assets Held-in-trust	9,400		9,400		9,000
Non-Recourse Debt	82		82		21
On-balance sheet variable interest entities | Commercial Automotive Industry Sector
Variable Interest Entity [Line Items]
Total assets	6,257		6,257		8,009
Liabilities	2,150		2,150		3,049
Off-balance sheet variable interest entities
Variable Interest Entity [Line Items]
Total assets	27,202		27,202		29,487
Liabilities	6,983		6,983		9,497
Assets sold to nonconsolidated VIEs	276		276		417
Variable interest entity, maximum loss exposure	1,768		1,768		1,837
Off-balance sheet variable interest entities | Consumer Automotive Industry Sector
Variable Interest Entity [Line Items]
Total assets	15		15		23
Liabilities	0		0		0
Assets sold to nonconsolidated VIEs	276		276		417
Variable interest entity, maximum loss exposure	290		290		440
Held-to-maturity securities	13		13		21
Other assets	2		2		2
Off-balance sheet variable interest entities | Commercial Other Industry Sector
Variable Interest Entity [Line Items]
Total assets	1,170		1,170		1,079
Liabilities	402		402		378
Assets sold to nonconsolidated VIEs	0		0		0
Variable interest entity, maximum loss exposure	$ 1,478		$ 1,478		1,397
Amount reconsolidated during the period
Variable Interest Entity [Line Items]
Assets of nonconsolidated variable interest entity					45
Amount reconsolidated during the period | Consumer Automotive Industry Sector
Variable Interest Entity [Line Items]
Assets of nonconsolidated variable interest entity					$ 48