Securitizations and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Variable Interest Entity [Line Items]
Carrying value of total assets	$ 180,470	$ 182,165	$ 184,061
Carrying value of total liabilities	162,940	167,462
On-balance sheet variable interest entities
Variable Interest Entity [Line Items]
Carrying value of total assets	9,878	14,196
Carrying value of total liabilities	1,850	4,161
On-balance sheet variable interest entities | Consumer Automotive Industry Sector
Variable Interest Entity [Line Items]
Carrying value of total assets	18,448	17,833
Carrying value of total liabilities	1,964	3,103
Assets held-in-trust	10,900	9,900
Non-recourse debt	114	94
On-balance sheet variable interest entities | Commercial Automotive Industry Sector
Variable Interest Entity [Line Items]
Carrying value of total assets	2,306	6,276
Carrying value of total liabilities	1	1,152
Off-balance sheet variable interest entities
Variable Interest Entity [Line Items]
Carrying value of total assets	22,317	25,404
Carrying value of total liabilities	2,631	4,784
Assets sold to nonconsolidated VIEs	0	0
Maximum exposure to loss in nonconsolidated VIEs	2,040	1,754
Off-balance sheet variable interest entities | Commercial Other Industry Sector
Variable Interest Entity [Line Items]
Carrying value of total assets	1,563	1,295
Carrying value of total liabilities	666	529
Assets sold to nonconsolidated VIEs	0	0
Maximum exposure to loss in nonconsolidated VIEs	$ 2,040	$ 1,754