Loans and Related Allowance for Credit Losses (Credit Quality Indicators for Automobile, Credit Card, Education and Other Consumer Loan Classes) (Details) - USD ($) $ in Millions		Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans	[1]	$ 294,457	$ 288,372
Automobile | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		1,493	6,612
Year two		5,958	3,403
Year three		3,000	3,765
Year four		3,246	1,874
Year five		1,569	738
Prior		735	243
Total loans		16,001	16,635
Automobile | Greater than or equal to 780 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		920	3,247
Year two		2,682	1,496
Year three		1,302	1,380
Year four		1,160	533
Year five		432	226
Prior		215	79
Total loans		6,711	6,961
Automobile | 720 to 779 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		405	2,119
Year two		1,984	983
Year three		856	1,030
Year four		879	499
Year five		410	195
Prior		193	62
Total loans		4,727	4,888
Automobile | 660 to 719 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		159	969
Year two		974	609
Year three		536	772
Year four		671	413
Year five		347	155
Prior		151	44
Total loans		2,838	2,962
Automobile | Less than 660 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		9	277
Year two		318	315
Year three		306	583
Year four		536	429
Year five		380	162
Prior		176	58
Total loans		1,725	1,824
Credit card | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans		6,403	6,564
Revolving Loans Converted to Term		61	62
Total loans		6,464	6,626
Credit card | Greater than or equal to 780 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans		1,797	1,815
Revolving Loans Converted to Term		2	2
Total loans		1,799	1,817
Credit card | 720 to 779 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans		1,779	1,836
Revolving Loans Converted to Term		8	9
Total loans		1,787	1,845
Credit card | 660 to 719 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans		1,793	1,856
Revolving Loans Converted to Term		18	19
Total loans		1,811	1,875
Credit card | Less than 660 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans		918	943
Revolving Loans Converted to Term		30	29
Total loans		948	972
Credit card | No FICO score available or required | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans		116	114
Revolving Loans Converted to Term		3	3
Total loans		119	117
Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		14	76
Year two		104	109
Year three		104	134
Year four		124	107
Year five		100	78
Prior		1,995	2,029
Total loans		2,441	2,533
Education | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		14	76
Year two		104	109
Year three		104	134
Year four		124	107
Year five		100	78
Prior		684	651
Total loans		1,130	1,155
Education | Greater than or equal to 780 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		1	37
Year two		56	60
Year three		55	77
Year four		69	62
Year five		57	48
Prior		404	392
Total loans		642	676
Education | 720 to 779 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		4	20
Year two		29	29
Year three		29	37
Year four		36	30
Year five		29	21
Prior		176	160
Total loans		303	297
Education | 660 to 719 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		4	7
Year two		9	9
Year three		9	11
Year four		11	11
Year five		10	7
Prior		75	73
Total loans		118	118
Education | Less than 660 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		1	1
Year two		1	1
Year three		2	2
Year four		2	2
Year five		2	2
Prior		28	25
Total loans		36	33
Education | No FICO score available or required | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		4	11
Year two		9	10
Year three		9	7
Year four		6	2
Year five		2
Prior		1	1
Total loans		31	31
Education | Other internal credit metrics
Financing Receivable, Credit Quality Indicator [Line Items]
Prior		1,311	1,378
Total loans		1,311	1,378
Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		204	776
Year two		654	541
Year three		441	575
Year four		472	274
Year five		209	75
Prior		153	116
Revolving Loans		3,377	3,347
Revolving Loans Converted to Term		29	23
Total loans		5,539	5,727
Other consumer | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		177	689
Year two		600	510
Year three		417	540
Year four		430	251
Year five		193	53
Prior		93	68
Revolving Loans		339	392
Revolving Loans Converted to Term			2
Total loans		2,249	2,505
Other consumer | Greater than or equal to 780 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		49	199
Year two		166	131
Year three		102	123
Year four		94	47
Year five		34	12
Prior		34	32
Revolving Loans		76	95
Revolving Loans Converted to Term			1
Total loans		555	640
Other consumer | 720 to 779 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		64	250
Year two		214	172
Year three		136	167
Year four		129	68
Year five		51	15
Prior		27	19
Revolving Loans		109	125
Total loans		730	816
Other consumer | 660 to 719 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		64	190
Year two		164	145
Year three		123	165
Year four		136	82
Year five		65	16
Prior		20	11
Revolving Loans		107	122
Total loans		679	731
Other consumer | Less than 660 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one			50
Year two		56	62
Year three		56	85
Year four		71	54
Year five		43	10
Prior		12	6
Revolving Loans		47	50
Revolving Loans Converted to Term			1
Total loans		285	318
Other consumer | Other internal credit metrics
Financing Receivable, Credit Quality Indicator [Line Items]
Year one		27	87
Year two		54	31
Year three		24	35
Year four		42	23
Year five		16	22
Prior		60	48
Revolving Loans		3,038	2,955
Revolving Loans Converted to Term		29	21
Total loans		$ 3,290	$ 3,222

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $1.3 billion, Loans held for investment of $1.4 billion and Other assets of $0.1 billion at March 31, 2022. Comparable amounts at December 31, 2021 were $1.9 billion, $1.5 billion and $0.1 billion, respectively.