Finance Receivables and Loans, Net - Schedule of Allowance for Credit Losses on Financing Receivables (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance, beginning balance	$ 3,572	$ 3,781	$ 3,587	$ 3,711	$ 3,711
Charge-offs	(744)	(677)	(2,178)	(1,907)	(2,720)
Recoveries	227	221	687	643
Net charge-offs	(517)	(456)	(1,491)	(1,264)
Write-downs from transfers to held-for-sale			(5)
Provision for credit losses	645	512	1,609	1,390
Other	0	0	0	0
Allowance, ending balance	3,700	3,837	3,700	3,837	3,587
Unfunded Loan Commitment
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Provision for credit losses		(4)		(9)
Consumer
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Charge-offs			(2,176)		(2,590)
Consumer | Automotive
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance, beginning balance	3,055	3,064	3,083	3,020	3,020
Charge-offs	(683)	(602)	(1,976)	(1,634)	(2,284)
Recoveries	216	209	654	613
Net charge-offs	(467)	(393)	(1,322)	(1,021)
Write-downs from transfers to held-for-sale			(5)		(41)
Provision for credit losses	578	433	1,410	1,106
Other	0	0	0	(1)
Allowance, ending balance	3,166	3,104	3,166	3,104	3,083
Consumer | Consumer mortgage
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance, beginning balance	19	23	21	27	27
Charge-offs	0	0	(1)	(3)	(3)
Recoveries	1	2	3	7
Net charge-offs	1	2	2	4
Write-downs from transfers to held-for-sale			0
Provision for credit losses	(3)	(4)	(6)	(9)
Other	2	1	2	0
Allowance, ending balance	19	22	19	22	21
Consumer | Consumer other
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance, beginning balance	302	476	293	426	426
Charge-offs	(61)	(74)	(199)	(208)	(303)
Recoveries	9	6	23	18
Net charge-offs	(52)	(68)	(176)	(190)
Write-downs from transfers to held-for-sale			0		(174)
Provision for credit losses	58	68	191	239
Other	(1)	(2)	(1)	(1)
Allowance, ending balance	307	474	307	474	293
Fair value, option, carrying amount, financing receivable, no allowance						$ 3
Commercial
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Allowance, beginning balance	196	218	190	238	238
Charge-offs	0	(1)	(2)	(62)	(130)
Recoveries	1	4	7	5
Net charge-offs	1	3	5	(57)
Write-downs from transfers to held-for-sale			0
Provision for credit losses	12	15	14	54
Other	(1)	1	(1)	2
Allowance, ending balance	$ 208	$ 237	208	$ 237	190
Commercial | Automotive
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Charge-offs			$ (2)		(24)
Commercial | Consumer other
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss [Roll Forward]
Charge-offs					$ (106)