Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators Commercial) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Total finance receivables and loans	$ 112,217	$ 118,534
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	979	2,711
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2,096	2,122
Financing Receivable, Originated Two Years before Latest Fiscal Year	1,942	1,399
Financing Receivable, Originated Three Years before Latest Fiscal Year	1,084	1,272
Financing Receivable, Originated Four Years before Latest Fiscal Year	893	977
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1,479	902
Financing Receivable, Revolving	12,963	19,807
Revolving loans converted to term	132	142
Total finance receivables and loans	21,568	29,332
Automotive loan | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	230	920
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	363	245
Financing Receivable, Originated Two Years before Latest Fiscal Year	224	117
Financing Receivable, Originated Three Years before Latest Fiscal Year	87	143
Financing Receivable, Originated Four Years before Latest Fiscal Year	90	86
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	112	52
Financing Receivable, Revolving	10,197	17,519
Revolving loans converted to term	0	0
Total finance receivables and loans	11,303	19,082
Automotive loan | Pass | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	218	869
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	353	220
Financing Receivable, Originated Two Years before Latest Fiscal Year	201	58
Financing Receivable, Originated Three Years before Latest Fiscal Year	45	91
Financing Receivable, Originated Four Years before Latest Fiscal Year	52	76
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	73	34
Financing Receivable, Revolving	9,261	15,433
Revolving loans converted to term	0	0
Total finance receivables and loans	10,203	16,781
Automotive loan | Special Mention | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	12	48
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	9	23
Financing Receivable, Originated Two Years before Latest Fiscal Year	23	59
Financing Receivable, Originated Three Years before Latest Fiscal Year	41	52
Financing Receivable, Originated Four Years before Latest Fiscal Year	38	9
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	37	18
Financing Receivable, Revolving	887	2,013
Revolving loans converted to term	0	0
Total finance receivables and loans	1,047	2,222
Automotive loan | Substandard | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	3
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1	2
Financing Receivable, Originated Two Years before Latest Fiscal Year	0	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	1	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0	1
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	2	0
Financing Receivable, Revolving	49	72
Revolving loans converted to term	0	0
Total finance receivables and loans	53	78
Automotive loan | Doubtful | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0	0
Financing Receivable, Revolving	0	1
Revolving loans converted to term	0	0
Total finance receivables and loans	0	1
Consumer other | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	297	645
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	564	817
Financing Receivable, Originated Two Years before Latest Fiscal Year	720	367
Financing Receivable, Originated Three Years before Latest Fiscal Year	221	514
Financing Receivable, Originated Four Years before Latest Fiscal Year	315	183
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	434	288
Financing Receivable, Revolving	2,763	2,288
Revolving loans converted to term	128	140
Total finance receivables and loans	5,442	5,242
Consumer other | Pass | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	297	536
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	457	622
Financing Receivable, Originated Two Years before Latest Fiscal Year	556	244
Financing Receivable, Originated Three Years before Latest Fiscal Year	194	210
Financing Receivable, Originated Four Years before Latest Fiscal Year	90	81
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	218	69
Financing Receivable, Revolving	2,675	2,142
Revolving loans converted to term	86	76
Total finance receivables and loans	4,573	3,980
Consumer other | Special Mention | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	76
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	75	169
Financing Receivable, Originated Two Years before Latest Fiscal Year	139	123
Financing Receivable, Originated Three Years before Latest Fiscal Year	27	190
Financing Receivable, Originated Four Years before Latest Fiscal Year	86	102
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	99	115
Financing Receivable, Revolving	71	123
Revolving loans converted to term	17	43
Total finance receivables and loans	514	941
Consumer other | Substandard | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	33
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	32	26
Financing Receivable, Originated Two Years before Latest Fiscal Year	25	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0	108
Financing Receivable, Originated Four Years before Latest Fiscal Year	138	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	90	77
Financing Receivable, Revolving	17	21
Revolving loans converted to term	25	20
Total finance receivables and loans	327	285
Consumer other | Doubtful | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0	6
Financing Receivable, Originated Four Years before Latest Fiscal Year	0	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	27	27
Financing Receivable, Revolving	0	2
Revolving loans converted to term	0	1
Total finance receivables and loans	27	36
Consumer other | Loss | Commercial
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	1
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	0
Financing Receivable, Revolving	0
Revolving loans converted to term	0
Total finance receivables and loans	1
Commercial real estate | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	452	1,146
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1,169	1,060
Financing Receivable, Originated Two Years before Latest Fiscal Year	998	915
Financing Receivable, Originated Three Years before Latest Fiscal Year	776	615
Financing Receivable, Originated Four Years before Latest Fiscal Year	488	708
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	933	562
Financing Receivable, Revolving	3	0
Revolving loans converted to term	4	2
Total finance receivables and loans	4,823	5,008
Commercial real estate | Pass | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	452	1,108
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1,111	928
Financing Receivable, Originated Two Years before Latest Fiscal Year	867	799
Financing Receivable, Originated Three Years before Latest Fiscal Year	731	580
Financing Receivable, Originated Four Years before Latest Fiscal Year	457	651
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	869	512
Financing Receivable, Revolving	3	0
Revolving loans converted to term	4	2
Total finance receivables and loans	4,494	4,580
Commercial real estate | Special Mention | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	38
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	58	132
Financing Receivable, Originated Two Years before Latest Fiscal Year	131	116
Financing Receivable, Originated Three Years before Latest Fiscal Year	45	32
Financing Receivable, Originated Four Years before Latest Fiscal Year	31	49
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	49	43
Financing Receivable, Revolving	0	0
Revolving loans converted to term	0	0
Total finance receivables and loans	314	410
Commercial real estate | Substandard | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0	3
Financing Receivable, Originated Four Years before Latest Fiscal Year	0	6
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	13	7
Financing Receivable, Revolving	0	0
Revolving loans converted to term	0	0
Total finance receivables and loans	13	16
Commercial real estate | Doubtful | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0	0
Financing Receivable, Originated Four Years before Latest Fiscal Year	0	2
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	2	0
Financing Receivable, Revolving	0	0
Revolving loans converted to term	0	0
Total finance receivables and loans	$ 2	$ 2