Securitizations and Variable Interest Entities - Schedule of Variable Interest Entities (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Variable Interest Entity [Line Items]
Carrying value of total assets	$ 192,531	$ 196,392	$ 197,241
Carrying value of total liabilities	178,680	182,626
Assets sold to nonconsolidated VIEs	3,385	2,639
Maximum exposure to loss in nonconsolidated VIEs	6,681	5,458
Non-recourse debt	15,979	17,570
Held-to-maturity securities	4,548	4,680
Other assets	9,853	9,395
Equity securities	854	810
On-balance sheet variable interest entities
Variable Interest Entity [Line Items]
Carrying value of total assets	5,255	7,075
Carrying value of total liabilities	1,120	1,513
Non-recourse debt	1,117	1,509
Other assets	363	461
On-balance sheet variable interest entities | Consumer | Automotive
Variable Interest Entity [Line Items]
Carrying value of total assets	13,841	16,415
Carrying value of total liabilities	1,223	1,614
Assets sold to nonconsolidated VIEs	0	0
Maximum exposure to loss in nonconsolidated VIEs	0	0
Assets held-in-trust	8,600	9,300
On-balance sheet variable interest entities | Consumer | Automotive | Nonrecourse
Variable Interest Entity [Line Items]
Non-recourse debt	103	100
Off-balance sheet variable interest entities
Variable Interest Entity [Line Items]
Carrying value of total assets	16,600	19,012
Carrying value of total liabilities	2,250	2,588
Off-balance sheet variable interest entities | Consumer | Automotive
Variable Interest Entity [Line Items]
Carrying value of total assets	115	81
Carrying value of total liabilities	0	0
Assets sold to nonconsolidated VIEs	3,285	2,514
Maximum exposure to loss in nonconsolidated VIEs	3,400	2,595
Held-to-maturity securities	110	78
Other assets	5	3
Off-balance sheet variable interest entities | Consumer | Other
Variable Interest Entity [Line Items]
Carrying value of total assets	0	0
Carrying value of total liabilities	0	0
Assets sold to nonconsolidated VIEs	100	125
Maximum exposure to loss in nonconsolidated VIEs	100	125
Off-balance sheet variable interest entities | Commercial | Other
Variable Interest Entity [Line Items]
Carrying value of total assets	2,644	2,516
Carrying value of total liabilities	1,027	974
Assets sold to nonconsolidated VIEs	0	0
Maximum exposure to loss in nonconsolidated VIEs	3,181	2,738
Equity securities	$ 47	$ 44