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		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total loans, net	[1]	$ 318,416		$ 318,416		$ 326,025
Gross charge-offs
Total		233	$ 222	808	$ 668
Updated FICO scores
Gross charge-offs
Year two				18
Year three				18
Year four				13
Year five				23
Prior				19
Total				91
Updated FICO scores | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		4,647		4,647		5,139
Year two		3,980		3,980		4,424
Year three		3,249		3,249		2,054
Year four		1,363		1,363		2,067
Year five		1,223		1,223		878
Prior		478		478		274
Total loans, net		14,940		14,940		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		2,221		2,221		2,390
Year two		1,776		1,776		2,162
Year three		1,653		1,653		922
Year four		624		624		760
Year five		456		456		241
Prior		127		127		75
Total loans, net		6,857		6,857		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		1,454		1,454		1,702
Year two		1,266		1,266		1,312
Year three		892		892		561
Year four		356		356		538
Year five		309		309		222
Prior		115		115		69
Total loans, net		4,392		4,392		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		804		804		854
Year two		677		677		660
Year three		456		456		341
Year four		218		218		401
Year five		228		228		187
Prior		100		100		56
Total loans, net		2,483		2,483		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		168		168		193
Year two		261		261		290
Year three		248		248		230
Year four		165		165		368
Year five		230		230		228
Prior		136		136		74
Total loans, net		1,208		1,208		1,383
Credit card
Gross charge-offs
Revolving Loans				212
Revolving Loans Converted to Term				20
Total				232
Credit card | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving Loans		6,994		6,994		7,010
Revolving Loans Converted to Term		66		66		59
Total loans, net		7,060		7,060		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		1,920		1,920		1,954
Revolving Loans Converted to Term		1		1		2
Total loans, net		1,921		1,921		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		1,967		1,967		1,994
Revolving Loans Converted to Term		5		5		6
Total loans, net		1,972		1,972		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		1,982		1,982		1,957
Revolving Loans Converted to Term		13		13		13
Total loans, net		1,995		1,995		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		1,016		1,016		1,001
Revolving Loans Converted to Term		44		44		35
Total loans, net		1,060		1,060		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		109		104
Revolving Loans Converted to Term		3		3		3
Total loans, net		112		112		107
Education
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		75		75		126
Year two		165		165		97
Year three		86		86		88
Year four		74		74		105
Year five		89		89		85
Prior		1,531		1,531		1,672
Total loans, net		2,020		2,020		2,173
Gross charge-offs
Year three				1
Year four				1
Year five				1
Prior				10
Total				13
Education | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		75		75		126
Year two		165		165		97
Year three		86		86		88
Year four		74		74		105
Year five		89		89		85
Prior		570		570		584
Total loans, net		1,059		1,059		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		7		7		42
Year two		25		25		53
Year three		8		8		48
Year four		11		11		61
Year five		19		19		51
Prior		133		133		357
Total loans, net		203		203		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		20		20		39
Year two		45		45		27
Year three		25		25		24
Year four		25		25		30
Year five		32		32		24
Prior		182		182		143
Total loans, net		329		329		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		19		19		21
Year two		45		45		8
Year three		27		27		8
Year four		23		23		9
Year five		29		29		8
Prior		156		156		59
Total loans, net		299		299		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		9		9		4
Year two		37		37		1
Year three		16		16		1
Year four		8		8		2
Year five		7		7		2
Prior		94		94		24
Total loans, net		171		171		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		20		20		20
Year two		13		13		8
Year three		10		10		7
Year four		7		7		3
Year five		2		2
Prior		5		5		1
Total loans, net		57		57		39
Education | Other internal credit metrics
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Prior		961		961		1,088
Total loans, net		961		961		1,088
Other consumer
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		599		599		912
Year two		653		653		420
Year three		259		259		266
Year four		188		188		248
Year five		165		165		89
Prior		75		75		76
Revolving Loans		2,491		2,491		2,995
Revolving Loans Converted to Term		16		16		20
Total loans, net		4,446		4,446		5,026
Gross charge-offs
Year one				54
Year two				16
Year three				14
Year four				12
Year five				12
Prior				7
Revolving Loans				8
Revolving Loans Converted to Term				1
Total				124
Other consumer | Using FICO Credit Metric
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		567		567		787
Year two		546		546		377
Year three		227		227		226
Year four		115		115		214
Year five		93		93		82
Prior		52		52		47
Revolving Loans		252		252		275
Revolving Loans Converted to Term		6		6		8
Total loans, net		1,858		1,858		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		195		195		224
Year two		151		151		97
Year three		57		57		53
Year four		27		27		46
Year five		20		20		14
Prior		14		14		18
Revolving Loans		40		40		47
Revolving Loans Converted to Term		2		2		2
Total loans, net		506		506		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		244		244		302
Year two		189		189		122
Year three		68		68		68
Year four		32		32		62
Year five		25		25		20
Prior		14		14		15
Revolving Loans		81		81		89
Revolving Loans Converted to Term		1		1		2
Total loans, net		654		654		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		117		117		229
Year two		155		155		110
Year three		68		68		68
Year four		35		35		66
Year five		29		29		28
Prior		14		14		8
Revolving Loans		88		88		95
Revolving Loans Converted to Term		2		2		2
Total loans, net		508		508		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		11		11		32
Year two		51		51		48
Year three		34		34		37
Year four		21		21		40
Year five		19		19		20
Prior		10		10		6
Revolving Loans		43		43		44
Revolving Loans Converted to Term		1		1		2
Total loans, net		190		190		229
Other consumer | Other internal credit metrics
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Year one		32		32		125
Year two		107		107		43
Year three		32		32		40
Year four		73		73		34
Year five		72		72		7
Prior		23		23		29
Revolving Loans		2,239		2,239		2,720
Revolving Loans Converted to Term		10		10		12
Total loans, net		$ 2,588		$ 2,588		$ 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 $1.2 billion and Other assets of $0.1 billion at September 30, 2023. Comparable amounts at December 31, 2022 were $0.9 billion, $1.3 billion and $0.1 billion, respectively.