Securitizations and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 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
Assets	182,527	$ 180,117	$ 180,644
Liabilities	169,008		166,228
Held-to-maturity securities	1,497		1,568
Other assets	7,978		6,073
On-balance sheet variable interest entities
Variable Interest Entity [Line Items]
Assets	19,236		19,344
Liabilities	8,160		9,098
Other assets	871		787
On-balance sheet variable interest entities | Consumer Automotive Industry Sector
Variable Interest Entity [Line Items]
Assets	21,106		20,376
Liabilities	5,161		6,070
Assets Held-in-trust	9,400		9,000
Non-Recourse Debt	51		21
On-balance sheet variable interest entities | Commercial Automotive Industry Sector
Variable Interest Entity [Line Items]
Assets	7,497		8,009
Liabilities	3,050		3,049
Off-balance sheet variable interest entities
Variable Interest Entity [Line Items]
Assets	29,780		29,487
Liabilities	8,625		9,497
Assets sold to nonconsolidated VIEs	340		417
Variable interest entity, maximum loss exposure	1,793		1,837
Off-balance sheet variable interest entities | Consumer Automotive Industry Sector
Variable Interest Entity [Line Items]
Assets	18		23
Liabilities	0		0
Assets sold to nonconsolidated VIEs	340		417
Variable interest entity, maximum loss exposure	358		440
Held-to-maturity securities	17		21
Other assets	1		2
Off-balance sheet variable interest entities | Commercial Other Industry Sector
Variable Interest Entity [Line Items]
Assets	1,159		1,079
Liabilities	414		378
Assets sold to nonconsolidated VIEs	0		0
Variable interest entity, maximum loss exposure	$ 1,435		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