Loans and Related Allowance for Credit Losses (Credit Quality Indicators for Automobile, Credit Card, Education and Other Consumer Loan Classes) (Details) - USD ($) $ in Millions	Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net	$ 288,372	[1]	$ 241,928	[1]	$ 239,843
Automobile | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	6,612		3,714
Year two	3,403		5,494
Year three	3,765		2,878
Year four	1,874		1,361
Year five	738		609
Prior	243		162
Total loans, net	16,635		14,218
Automobile | FICO Score, Greater Than Or Equal To 780 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	3,247		1,807
Year two	1,496		1,915
Year three	1,380		807
Year four	533		452
Year five	226		246
Prior	79		58
Total loans, net	6,961		5,285
Automobile | FICO Score, 720 to 779 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	2,119		1,098
Year two	983		1,581
Year three	1,030		789
Year four	499		381
Year five	195		167
Prior	62		44
Total loans, net	4,888		4,060
Automobile | FICO Score, 660 to 719 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	969		617
Year two	609		1,222
Year three	772		684
Year four	413		288
Year five	155		109
Prior	44		31
Total loans, net	2,962		2,951
Automobile | FICO Score, Less Than 660 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	277		192
Year two	315		776
Year three	583		598
Year four	429		240
Year five	162		87
Prior	58		29
Total loans, net	1,824		1,922
Credit card | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans	6,564		6,120
Revolving Loans Converted to Term	62		95
Total loans, net	6,626		6,215
Credit card | FICO Score, Greater Than Or Equal To 780 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans	1,815		1,635
Revolving Loans Converted to Term	2		3
Total loans, net	1,817		1,638
Credit card | FICO Score, 720 to 779 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans	1,836		1,724
Revolving Loans Converted to Term	9		11
Total loans, net	1,845		1,735
Credit card | FICO Score, 660 to 719 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans	1,856		1,765
Revolving Loans Converted to Term	19		26
Total loans, net	1,875		1,791
Credit card | FICO Score, Less Than 660 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans	943		902
Revolving Loans Converted to Term	29		51
Total loans, net	972		953
Credit card | No FICO Score Available Or Required | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving Loans	114		94
Revolving Loans Converted to Term	3		4
Total loans, net	117		98
Education
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	76		92
Year two	109		163
Year three	134		135
Year four	107		101
Year five	78		78
Prior	2,029		2,377
Total loans, net	2,533		2,946
Education | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	76		92
Year two	109		163
Year three	134		135
Year four	107		101
Year five	78		78
Prior	651		746
Total loans, net	1,155		1,315
Education | FICO Score, Greater Than Or Equal To 780 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	37		34
Year two	60		90
Year three	77		74
Year four	62		59
Year five	48		50
Prior	392		428
Total loans, net	676		735
Education | FICO Score, 720 to 779 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	20		24
Year two	29		46
Year three	37		38
Year four	30		28
Year five	21		20
Prior	160		190
Total loans, net	297		346
Education | FICO Score, 660 to 719 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	7		15
Year two	9		15
Year three	11		14
Year four	11		9
Year five	7		6
Prior	73		90
Total loans, net	118		149
Education | FICO Score, Less Than 660 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	1		3
Year two	1		2
Year three	2		3
Year four	2		2
Year five	2		2
Prior	25		37
Total loans, net	33		49
Education | No FICO Score Available Or Required | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	11		16
Year two	10		10
Year three	7		6
Year four	2		3
Prior	1		1
Total loans, net	31		36
Education | Other Internal Credit Metrics
Financing Receivable, Credit Quality Indicator [Line Items]
Prior	1,378		1,631
Total loans, net	1,378		1,631
Other consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	776		581
Year two	541		763
Year three	575		304
Year four	274		95
Year five	75		75
Prior	116		161
Revolving Loans	3,347		2,713
Revolving Loans Converted to Term	23		6
Total loans, net	5,727		4,698
Other consumer | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	689		514
Year two	510		730
Year three	540		267
Year four	251		69
Year five	53		15
Prior	68		86
Revolving Loans	392		379
Revolving Loans Converted to Term	2		3
Total loans, net	2,505		2,063
Other consumer | FICO Score, Greater Than Or Equal To 780 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	199		162
Year two	131		187
Year three	123		63
Year four	47		21
Year five	12		5
Prior	32		42
Revolving Loans	95		86
Revolving Loans Converted to Term	1		1
Total loans, net	640		567
Other consumer | FICO Score, 720 to 779 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	250		197
Year two	172		247
Year three	167		82
Year four	68		22
Year five	15		5
Prior	19		22
Revolving Loans	125		123
Total loans, net	816		698
Other consumer | FICO Score, 660 to 719 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	190		127
Year two	145		210
Year three	165		81
Year four	82		17
Year five	16		3
Prior	11		14
Revolving Loans	122		117
Revolving Loans Converted to Term			1
Total loans, net	731		570
Other consumer | FICO Score, Less Than 660 | Using FICO Credit Metric
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	50		28
Year two	62		86
Year three	85		41
Year four	54		9
Year five	10		2
Prior	6		8
Revolving Loans	50		53
Revolving Loans Converted to Term	1		1
Total loans, net	318		228
Other consumer | Other Internal Credit Metrics
Financing Receivable, Credit Quality Indicator [Line Items]
Year one	87		67
Year two	31		33
Year three	35		37
Year four	23		26
Year five	22		60
Prior	48		75
Revolving Loans	2,955		2,334
Revolving Loans Converted to Term	21		3
Total loans, net	$ 3,222		$ 2,635

[1] Our consolidated assets included the following for which we have elected the fair value option: Loans held for sale of $1.9 billion, Loans of $1.5 billion and Other assets of $0.1 billion at December 31, 2021 and Loans held for sale of $1.2 billion, Loans of $1.4 billion and Other assets of $0.1 billion at December 31, 2020.