Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators Commercial) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	$ 118,534	$ 128,231
Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	2,711
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2,122
Financing Receivable, Originated Two Years before Latest Fiscal Year	1,399
Financing Receivable, Originated Three Years before Latest Fiscal Year	1,272
Financing Receivable, Originated Four Years before Latest Fiscal Year	977
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	902
Financing Receivable, Revolving	19,807
Converted to term loans	142
Finance receivables and loans, net	29,332	38,307
Pass | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net		34,080
Automotive loan | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	920
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	245
Financing Receivable, Originated Two Years before Latest Fiscal Year	117
Financing Receivable, Originated Three Years before Latest Fiscal Year	143
Financing Receivable, Originated Four Years before Latest Fiscal Year	86
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	52
Financing Receivable, Revolving	17,519
Converted to term loans	0
Finance receivables and loans, net	19,082	28,332
Automotive loan | Pass | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	869
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	220
Financing Receivable, Originated Two Years before Latest Fiscal Year	58
Financing Receivable, Originated Three Years before Latest Fiscal Year	91
Financing Receivable, Originated Four Years before Latest Fiscal Year	76
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	34
Financing Receivable, Revolving	15,433
Converted to term loans	0
Finance receivables and loans, net	16,781	25,235
Automotive loan | Special Mention | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	48
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	23
Financing Receivable, Originated Two Years before Latest Fiscal Year	59
Financing Receivable, Originated Three Years before Latest Fiscal Year	52
Financing Receivable, Originated Four Years before Latest Fiscal Year	9
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	18
Financing Receivable, Revolving	2,013
Converted to term loans	0
Finance receivables and loans, net	2,222
Automotive loan | Substandard | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	3
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	1
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0
Financing Receivable, Revolving	72
Converted to term loans	0
Finance receivables and loans, net	78
Automotive loan | Doubtful | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0
Financing Receivable, Revolving	1
Converted to term loans	0
Finance receivables and loans, net	1
Other loan | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	645
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	817
Financing Receivable, Originated Two Years before Latest Fiscal Year	367
Financing Receivable, Originated Three Years before Latest Fiscal Year	514
Financing Receivable, Originated Four Years before Latest Fiscal Year	183
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	288
Financing Receivable, Revolving	2,288
Converted to term loans	140
Finance receivables and loans, net	5,242	5,014
Other loan | Pass | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	536
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	622
Financing Receivable, Originated Two Years before Latest Fiscal Year	244
Financing Receivable, Originated Three Years before Latest Fiscal Year	210
Financing Receivable, Originated Four Years before Latest Fiscal Year	81
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	69
Financing Receivable, Revolving	2,142
Converted to term loans	76
Finance receivables and loans, net	3,980	4,225
Other loan | Special Mention | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	76
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	169
Financing Receivable, Originated Two Years before Latest Fiscal Year	123
Financing Receivable, Originated Three Years before Latest Fiscal Year	190
Financing Receivable, Originated Four Years before Latest Fiscal Year	102
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	115
Financing Receivable, Revolving	123
Converted to term loans	43
Finance receivables and loans, net	941
Other loan | Substandard | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	33
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	26
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	108
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	77
Financing Receivable, Revolving	21
Converted to term loans	20
Finance receivables and loans, net	285
Other loan | Doubtful | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	6
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	27
Financing Receivable, Revolving	2
Converted to term loans	1
Finance receivables and loans, net	36
Real estate-backed loan | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	1,146
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1,060
Financing Receivable, Originated Two Years before Latest Fiscal Year	915
Financing Receivable, Originated Three Years before Latest Fiscal Year	615
Financing Receivable, Originated Four Years before Latest Fiscal Year	708
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	562
Financing Receivable, Revolving	0
Converted to term loans	2
Finance receivables and loans, net	5,008	4,961
Real estate-backed loan | Pass | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	1,108
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	928
Financing Receivable, Originated Two Years before Latest Fiscal Year	799
Financing Receivable, Originated Three Years before Latest Fiscal Year	580
Financing Receivable, Originated Four Years before Latest Fiscal Year	651
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	512
Financing Receivable, Revolving	0
Converted to term loans	2
Finance receivables and loans, net	4,580	$ 4,620
Real estate-backed loan | Special Mention | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	38
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	132
Financing Receivable, Originated Two Years before Latest Fiscal Year	116
Financing Receivable, Originated Three Years before Latest Fiscal Year	32
Financing Receivable, Originated Four Years before Latest Fiscal Year	49
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	43
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	410
Real estate-backed loan | Substandard | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	3
Financing Receivable, Originated Four Years before Latest Fiscal Year	6
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	7
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	16
Real estate-backed loan | Doubtful | Commercial portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	2
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	$ 2