Loans and Related Allowance for Credit Losses (Credit Quality Indicators for Automobile, Credit Card, Education and Other Consumer Loan Classes) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total loans, net	[1]	$ 326,475	$ 326,025
Updated FICO scores
Gross charge-offs
Year two		5
Year three		6
Year four		5
Year five		10
Prior		7
Total		33
Updated FICO scores | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		1,672	5,139
Year two		4,778	4,424
Year three		4,022	2,054
Year four		1,808	2,067
Year five		1,761	878
Prior		882	274
Total loans, net		14,923	14,836
Updated FICO scores | Greater than or equal to 780 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		971	2,390
Year two		1,982	2,162
Year three		1,953	922
Year four		800	760
Year five		634	241
Prior		234	75
Total loans, net		6,574	6,550
Updated FICO scores | 720 to 779 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		474	1,702
Year two		1,647	1,312
Year three		1,176	561
Year four		491	538
Year five		457	222
Prior		218	69
Total loans, net		4,463	4,404
Updated FICO scores | 660 to 719 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		212	854
Year two		890	660
Year three		600	341
Year four		303	401
Year five		340	187
Prior		186	56
Total loans, net		2,531	2,499
Updated FICO scores | Less than 660 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		15	193
Year two		259	290
Year three		293	230
Year four		214	368
Year five		330	228
Prior		244	74
Total loans, net		1,355	1,383
Credit card
Gross charge-offs
Revolving Loans		67
Revolving Loans Converted to Term		7
Total		74
Credit card | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving Loans		6,904	7,010
Revolving Loans Converted to Term		57	59
Total loans, net		6,961	7,069
Credit card | Greater than or equal to 780 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving Loans		1,876	1,954
Revolving Loans Converted to Term		1	2
Total loans, net		1,877	1,956
Credit card | 720 to 779 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving Loans		1,913	1,994
Revolving Loans Converted to Term		5	6
Total loans, net		1,918	2,000
Credit card | 660 to 719 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving Loans		1,985	1,957
Revolving Loans Converted to Term		13	13
Total loans, net		1,998	1,970
Credit card | Less than 660 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving Loans		1,021	1,001
Revolving Loans Converted to Term		35	35
Total loans, net		1,056	1,036
Credit card | No FICO score available or required | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving Loans		109	104
Revolving Loans Converted to Term		3	3
Total loans, net		112	107
Education
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		25	126
Year two		171	97
Year three		93	88
Year four		83	105
Year five		99	85
Prior		1,660	1,672
Total loans, net		2,131	2,173
Gross charge-offs
Year five		1
Prior		3
Total		4
Education | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		25	126
Year two		171	97
Year three		93	88
Year four		83	105
Year five		99	85
Prior		637	584
Total loans, net		1,108	1,085
Education | Greater than or equal to 780 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		2	42
Year two		87	53
Year three		51	48
Year four		46	61
Year five		57	51
Prior		385	357
Total loans, net		628	612
Education | 720 to 779 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		9	39
Year two		55	27
Year three		27	24
Year four		23	30
Year five		29	24
Prior		161	143
Total loans, net		304	287
Education | 660 to 719 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		7	21
Year two		19	8
Year three		8	8
Year four		8	9
Year five		9	8
Prior		65	59
Total loans, net		116	113
Education | Less than 660 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		2	4
Year two		2	1
Year three		1	1
Year four		1	2
Year five		2	2
Prior		25	24
Total loans, net		33	34
Education | No FICO score available or required | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		5	20
Year two		8	8
Year three		6	7
Year four		5	3
Year five		2
Prior		1	1
Total loans, net		27	39
Education | Other internal credit metrics
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Prior		1,023	1,088
Total loans, net		1,023	1,088
Other consumer
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		218	912
Year two		831	420
Year three		356	266
Year four		219	248
Year five		241	89
Prior		125	76
Revolving Loans		2,759	2,995
Revolving Loans Converted to Term		29	20
Total loans, net		4,778	5,026
Gross charge-offs
Year one		16
Year two		3
Year three		5
Year four		4
Year five		6
Prior		4
Revolving Loans		4
Total		42
Other consumer | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		212	787
Year two		705	377
Year three		320	226
Year four		183	214
Year five		166	82
Prior		96	47
Revolving Loans		257	275
Revolving Loans Converted to Term		8	8
Total loans, net		1,947	2,016
Other consumer | Greater than or equal to 780 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		57	224
Year two		203	97
Year three		78	53
Year four		41	46
Year five		34	14
Prior		24	18
Revolving Loans		41	47
Revolving Loans Converted to Term		2	2
Total loans, net		480	501
Other consumer | 720 to 779 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		93	302
Year two		263	122
Year three		101	68
Year four		53	62
Year five		47	20
Prior		25	15
Revolving Loans		82	89
Revolving Loans Converted to Term		2	2
Total loans, net		666	680
Other consumer | 660 to 719 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		62	229
Year two		191	110
Year three		96	68
Year four		56	66
Year five		51	28
Prior		27	8
Revolving Loans		90	95
Revolving Loans Converted to Term		2	2
Total loans, net		575	606
Other consumer | Less than 660 | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one			32
Year two		48	48
Year three		45	37
Year four		33	40
Year five		34	20
Prior		20	6
Revolving Loans		44	44
Revolving Loans Converted to Term		2	2
Total loans, net		226	229
Other consumer | Other internal credit metrics
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		6	125
Year two		126	43
Year three		36	40
Year four		36	34
Year five		75	7
Prior		29	29
Revolving Loans		2,502	2,720
Revolving Loans Converted to Term		21	12
Total loans, net		$ 2,831	$ 3,010

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $0.9 billion, Loans held for investment of $1.3 billion and Other assets of $0.1 billion at both March 31, 2023 and December 31, 2022.