Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators Commercial) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total finance receivables and loans	$ 114,471	$ 118,534
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	1,596	2,711
Year two, originated, fiscal year before current fiscal year	1,984	2,122
Year three, originated, two years before current fiscal year	1,853	1,399
Year four, originated, three years before current fiscal year	927	1,272
Year five, originated, four years before current fiscal year	780	977
Originated, more than five years before current fiscal year	1,258	902
Revolving loans	10,880	19,807
Revolving loans converted to term	141	142
Total finance receivables and loans	19,419	29,332
Automotive loan | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	287	920
Year two, originated, fiscal year before current fiscal year	252	245
Year three, originated, two years before current fiscal year	199	117
Year four, originated, three years before current fiscal year	76	143
Year five, originated, four years before current fiscal year	65	86
Originated, more than five years before current fiscal year	93	52
Revolving loans	7,800	17,519
Revolving loans converted to term	0	0
Total finance receivables and loans	8,772	19,082
Automotive loan | Pass | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	278	869
Year two, originated, fiscal year before current fiscal year	247	220
Year three, originated, two years before current fiscal year	182	58
Year four, originated, three years before current fiscal year	49	91
Year five, originated, four years before current fiscal year	32	76
Originated, more than five years before current fiscal year	64	34
Revolving loans	7,232	15,433
Revolving loans converted to term	0	0
Total finance receivables and loans	8,084	16,781
Automotive loan | Special Mention | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	9	48
Year two, originated, fiscal year before current fiscal year	4	23
Year three, originated, two years before current fiscal year	17	59
Year four, originated, three years before current fiscal year	26	52
Year five, originated, four years before current fiscal year	33	9
Originated, more than five years before current fiscal year	29	18
Revolving loans	525	2,013
Revolving loans converted to term	0	0
Total finance receivables and loans	643	2,222
Automotive loan | Substandard | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	0	3
Year two, originated, fiscal year before current fiscal year	1	2
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	1	0
Year five, originated, four years before current fiscal year	0	1
Originated, more than five years before current fiscal year	0	0
Revolving loans	43	72
Revolving loans converted to term	0	0
Total finance receivables and loans	45	78
Automotive loan | Doubtful | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year		0
Year two, originated, fiscal year before current fiscal year		0
Year three, originated, two years before current fiscal year		0
Year four, originated, three years before current fiscal year		0
Year five, originated, four years before current fiscal year		0
Originated, more than five years before current fiscal year		0
Revolving loans		1
Revolving loans converted to term		0
Total finance receivables and loans		1
Other | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	519	645
Year two, originated, fiscal year before current fiscal year	574	817
Year three, originated, two years before current fiscal year	699	367
Year four, originated, three years before current fiscal year	146	514
Year five, originated, four years before current fiscal year	298	183
Originated, more than five years before current fiscal year	410	288
Revolving loans	3,077	2,288
Revolving loans converted to term	136	140
Total finance receivables and loans	5,859	5,242
Other | Pass | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	519	536
Year two, originated, fiscal year before current fiscal year	468	622
Year three, originated, two years before current fiscal year	489	244
Year four, originated, three years before current fiscal year	125	210
Year five, originated, four years before current fiscal year	138	81
Originated, more than five years before current fiscal year	155	69
Revolving loans	2,948	2,142
Revolving loans converted to term	96	76
Total finance receivables and loans	4,938	3,980
Other | Special Mention | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	0	76
Year two, originated, fiscal year before current fiscal year	75	169
Year three, originated, two years before current fiscal year	114	123
Year four, originated, three years before current fiscal year	21	190
Year five, originated, four years before current fiscal year	21	102
Originated, more than five years before current fiscal year	138	115
Revolving loans	115	123
Revolving loans converted to term	15	43
Total finance receivables and loans	499	941
Other | Substandard | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	0	33
Year two, originated, fiscal year before current fiscal year	24	26
Year three, originated, two years before current fiscal year	96	0
Year four, originated, three years before current fiscal year	0	108
Year five, originated, four years before current fiscal year	139	0
Originated, more than five years before current fiscal year	90	77
Revolving loans	10	21
Revolving loans converted to term	25	20
Total finance receivables and loans	384	285
Other | Doubtful | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	0	0
Year two, originated, fiscal year before current fiscal year	7	0
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	0	6
Year five, originated, four years before current fiscal year	0	0
Originated, more than five years before current fiscal year	27	27
Revolving loans	4	2
Revolving loans converted to term	0	1
Total finance receivables and loans	38	36
Commercial real estate | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	790	1,146
Year two, originated, fiscal year before current fiscal year	1,158	1,060
Year three, originated, two years before current fiscal year	955	915
Year four, originated, three years before current fiscal year	705	615
Year five, originated, four years before current fiscal year	417	708
Originated, more than five years before current fiscal year	755	562
Revolving loans	3	0
Revolving loans converted to term	5	2
Total finance receivables and loans	4,788	5,008
Commercial real estate | Pass | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	784	1,108
Year two, originated, fiscal year before current fiscal year	1,153	928
Year three, originated, two years before current fiscal year	837	799
Year four, originated, three years before current fiscal year	698	580
Year five, originated, four years before current fiscal year	398	651
Originated, more than five years before current fiscal year	721	512
Revolving loans	3	0
Revolving loans converted to term	5	2
Total finance receivables and loans	4,599	4,580
Commercial real estate | Special Mention | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	6	38
Year two, originated, fiscal year before current fiscal year	5	132
Year three, originated, two years before current fiscal year	118	116
Year four, originated, three years before current fiscal year	7	32
Year five, originated, four years before current fiscal year	19	49
Originated, more than five years before current fiscal year	24	43
Revolving loans	0	0
Revolving loans converted to term	0	0
Total finance receivables and loans	179	410
Commercial real estate | Substandard | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year	0	0
Year two, originated, fiscal year before current fiscal year	0	0
Year three, originated, two years before current fiscal year	0	0
Year four, originated, three years before current fiscal year	0	3
Year five, originated, four years before current fiscal year	0	6
Originated, more than five years before current fiscal year	10	7
Revolving loans	0	0
Revolving loans converted to term	0	0
Total finance receivables and loans	$ 10	16
Commercial real estate | Doubtful | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Year one, originated, current fiscal year		0
Year two, originated, fiscal year before current fiscal year		0
Year three, originated, two years before current fiscal year		0
Year four, originated, three years before current fiscal year		0
Year five, originated, four years before current fiscal year		2
Originated, more than five years before current fiscal year		0
Revolving loans		0
Revolving loans converted to term		0
Total finance receivables and loans		$ 2