Securitizations and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Variable Interest Entity [Line Items]
Carrying value of total assets	$ 179,184	$ 182,165	$ 185,270
Carrying value of total liabilities	161,895	167,462
On-balance sheet variable interest entities
Variable Interest Entity [Line Items]
Carrying value of total assets	8,493	14,196
Carrying value of total liabilities	1,439	4,161
On-balance sheet variable interest entities | Consumer Automotive Industry Sector
Variable Interest Entity [Line Items]
Carrying value of total assets	19,580	17,833
Carrying value of total liabilities	1,563	3,103
Assets held-in-trust	11,100	9,900
Non-recourse debt	124	94
On-balance sheet variable interest entities | Commercial Automotive Industry Sector
Variable Interest Entity [Line Items]
Carrying value of total assets		6,276
Carrying value of total liabilities		1,152
Off-balance sheet variable interest entities
Variable Interest Entity [Line Items]
Carrying value of total assets	21,268	25,404
Carrying value of total liabilities	2,296	4,784
Assets sold to nonconsolidated VIEs	0	0
Maximum exposure to loss in nonconsolidated VIEs	2,234	1,754
Off-balance sheet variable interest entities | Commercial Other Industry Sector
Variable Interest Entity [Line Items]
Carrying value of total assets	1,688	1,295
Carrying value of total liabilities	733	529
Assets sold to nonconsolidated VIEs	0	0
Maximum exposure to loss in nonconsolidated VIEs	$ 2,234	$ 1,754