Loans and Related Allowance for Credit Losses (Credit Quality Indicators for Automobile, Credit Card, Education and Other Consumer Loan Classes) (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2023	Dec. 31, 2022
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total loans, net	[1]	$ 321,761	$ 326,025
Updated FICO scores
Gross charge-offs
Year two		10
Year three		12
Year four		9
Year five		17
Prior		13
Total		61
Updated FICO scores | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		3,384	5,139
Year two		4,353	4,424
Year three		3,621	2,054
Year four		1,575	2,067
Year five		1,475	878
Prior		657	274
Total loans, net		15,065	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		1,706	2,390
Year two		1,907	2,162
Year three		1,846	922
Year four		728	760
Year five		554	241
Prior		180	75
Total loans, net		6,921	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		1,066	1,702
Year two		1,426	1,312
Year three		1,005	561
Year four		411	538
Year five		374	222
Prior		160	69
Total loans, net		4,442	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		538	854
Year two		766	660
Year three		510	341
Year four		251	401
Year five		275	187
Prior		137	56
Total loans, net		2,477	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		74	193
Year two		254	290
Year three		260	230
Year four		185	368
Year five		272	228
Prior		180	74
Total loans, net		1,225	1,383
Credit card
Gross charge-offs
Revolving Loans		141
Revolving Loans Converted to Term		13
Total		154
Credit card | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving Loans		7,032	7,010
Revolving Loans Converted to Term		60	59
Total loans, net		7,092	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		1,954	1,954
Revolving Loans Converted to Term		1	2
Total loans, net		1,955	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		2,022	1,994
Revolving Loans Converted to Term		5	6
Total loans, net		2,027	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		1,967	1,957
Revolving Loans Converted to Term		13	13
Total loans, net		1,980	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		983	1,001
Revolving Loans Converted to Term		38	35
Total loans, net		1,021	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		106	104
Revolving Loans Converted to Term		3	3
Total loans, net		109	107
Education
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		40	126
Year two		170	97
Year three		89	88
Year four		79	105
Year five		95	85
Prior		1,585	1,672
Total loans, net		2,058	2,173
Gross charge-offs
Year four		1
Year five		1
Prior		7
Total		9
Education | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		40	126
Year two		170	97
Year three		89	88
Year four		79	105
Year five		95	85
Prior		603	584
Total loans, net		1,076	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		15	42
Year two		94	53
Year three		50	48
Year four		44	61
Year five		56	51
Prior		373	357
Total loans, net		632	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		14	39
Year two		51	27
Year three		26	24
Year four		22	30
Year five		27	24
Prior		147	143
Total loans, net		287	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		6	21
Year two		16	8
Year three		7	8
Year four		7	9
Year five		8	8
Prior		59	59
Total loans, net		103	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		1	4
Year two		3	1
Year three		1	1
Year four		1	2
Year five		2	2
Prior		23	24
Total loans, net		31	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		4	20
Year two		6	8
Year three		5	7
Year four		5	3
Year five		2
Prior		1	1
Total loans, net		23	39
Education | Other internal credit metrics
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Prior		982	1,088
Total loans, net		982	1,088
Other consumer
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		418	912
Year two		738	420
Year three		304	266
Year four		165	248
Year five		200	89
Prior		97	76
Revolving Loans		2,611	2,995
Revolving Loans Converted to Term		22	20
Total loans, net		4,555	5,026
Gross charge-offs
Year one		32
Year two		9
Year three		10
Year four		8
Year five		9
Prior		5
Revolving Loans		6
Revolving Loans Converted to Term		1
Total		80
Other consumer | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		397	787
Year two		622	377
Year three		273	226
Year four		146	214
Year five		126	82
Prior		71	47
Revolving Loans		253	275
Revolving Loans Converted to Term		7	8
Total loans, net		1,895	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		136	224
Year two		183	97
Year three		69	53
Year four		34	46
Year five		27	14
Prior		19	18
Revolving Loans		41	47
Revolving Loans Converted to Term		2	2
Total loans, net		511	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		186	302
Year two		224	122
Year three		85	68
Year four		41	62
Year five		35	20
Prior		19	15
Revolving Loans		82	89
Revolving Loans Converted to Term		1	2
Total loans, net		673	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		70	229
Year two		166	110
Year three		80	68
Year four		45	66
Year five		39	28
Prior		19	8
Revolving Loans		88	95
Revolving Loans Converted to Term		2	2
Total loans, net		509	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		5	32
Year two		49	48
Year three		39	37
Year four		26	40
Year five		25	20
Prior		14	6
Revolving Loans		42	44
Revolving Loans Converted to Term		2	2
Total loans, net		202	229
Other consumer | Other internal credit metrics
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		21	125
Year two		116	43
Year three		31	40
Year four		19	34
Year five		74	7
Prior		26	29
Revolving Loans		2,358	2,720
Revolving Loans Converted to Term		15	12
Total loans, net		$ 2,660	$ 3,010

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $0.8 billion, Loans held for investment of $1.3 billion and Other assets of $0.1 billion at June 30, 2023. Comparable amounts at December 31, 2022 were $0.9 billion, $1.3 billion and $0.1 billion, respectively.