Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators Consumer) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	$ 113,076	$ 118,534
Consumer portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	87,391	89,202
Consumer portfolio segment | Excludes fair value option elected other loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	9,846	31,399
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	28,507	22,426
Financing Receivable, Originated Two Years before Latest Fiscal Year	19,709	14,509
Financing Receivable, Originated Three Years before Latest Fiscal Year	12,506	9,765
Financing Receivable, Originated Four Years before Latest Fiscal Year	8,101	5,143
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	8,386	5,604
Financing Receivable, Revolving	294	310
Converted to term loans	34	38
Finance receivables and loans, net	87,383	89,194
Consumer portfolio segment | Automotive loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	8,910	27,634
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	25,140	19,943
Financing Receivable, Originated Two Years before Latest Fiscal Year	17,852	12,730
Financing Receivable, Originated Three Years before Latest Fiscal Year	11,143	7,483
Financing Receivable, Originated Four Years before Latest Fiscal Year	6,353	3,953
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	4,600	1,925
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	73,998	73,668
Consumer portfolio segment | Real estate-backed loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	762	3,444
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	3,113	2,425
Financing Receivable, Originated Two Years before Latest Fiscal Year	1,817	1,765
Financing Receivable, Originated Three Years before Latest Fiscal Year	1,353	2,277
Financing Receivable, Originated Four Years before Latest Fiscal Year	1,745	1,189
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3,785	3,679
Financing Receivable, Revolving	294	310
Converted to term loans	34	38
Finance receivables and loans, net	12,903	15,127
Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	762	3,444
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	3,113	2,425
Financing Receivable, Originated Two Years before Latest Fiscal Year	1,817	1,765
Financing Receivable, Originated Three Years before Latest Fiscal Year	1,353	2,277
Financing Receivable, Originated Four Years before Latest Fiscal Year	1,745	1,189
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3,655	3,532
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	12,445	14,632
Consumer portfolio segment | Mortgage - Legacy
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	130	147
Financing Receivable, Revolving	294	310
Converted to term loans	34	38
Finance receivables and loans, net	458	495
Consumer portfolio segment | Other loan
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	490	407
Loans receivable, fair value	8	8	$ 10	$ 11
Consumer portfolio segment | Other loan | Excludes fair value option elected other loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	174	321
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	254	58
Financing Receivable, Originated Two Years before Latest Fiscal Year	40	14
Financing Receivable, Originated Three Years before Latest Fiscal Year	10	5
Financing Receivable, Originated Four Years before Latest Fiscal Year	3	1
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1	0
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	482	399
Current period | Consumer portfolio segment | Automotive loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	8,900	27,255
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	24,842	19,204
Financing Receivable, Originated Two Years before Latest Fiscal Year	17,404	12,129
Financing Receivable, Originated Three Years before Latest Fiscal Year	10,794	7,060
Financing Receivable, Originated Four Years before Latest Fiscal Year	6,114	3,678
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	4,362	1,766
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	72,416	71,092
Current period | Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	762	3,432
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	3,099	2,410
Financing Receivable, Originated Two Years before Latest Fiscal Year	1,805	1,744
Financing Receivable, Originated Three Years before Latest Fiscal Year	1,333	2,254
Financing Receivable, Originated Four Years before Latest Fiscal Year	1,733	1,177
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3,611	3,492
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	12,343	14,509
Current period | Consumer portfolio segment | Mortgage - Legacy
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	109	121
Financing Receivable, Revolving	286	303
Converted to term loans	31	36
Finance receivables and loans, net	426	460
Current period | Consumer portfolio segment | Other loan | Excludes fair value option elected other loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	173	306
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	248	53
Financing Receivable, Originated Two Years before Latest Fiscal Year	39	13
Financing Receivable, Originated Three Years before Latest Fiscal Year	10	4
Financing Receivable, Originated Four Years before Latest Fiscal Year	3	1
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1	0
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	474	377
Financing receivables, 30 to 59 days past due | Consumer portfolio segment | Automotive loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	9	281
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	205	466
Financing Receivable, Originated Two Years before Latest Fiscal Year	285	376
Financing Receivable, Originated Three Years before Latest Fiscal Year	223	264
Financing Receivable, Originated Four Years before Latest Fiscal Year	153	174
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	146	97
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	1,021	1,658
Financing receivables, 30 to 59 days past due | Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	10
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	11	9
Financing Receivable, Originated Two Years before Latest Fiscal Year	6	10
Financing Receivable, Originated Three Years before Latest Fiscal Year	7	11
Financing Receivable, Originated Four Years before Latest Fiscal Year	6	7
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	14	16
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	44	63
Financing receivables, 30 to 59 days past due | Consumer portfolio segment | Mortgage - Legacy
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	2	4
Financing Receivable, Revolving	2	2
Converted to term loans	1	0
Finance receivables and loans, net	5	6
Financing receivables, 30 to 59 days past due | Consumer portfolio segment | Other loan | Excludes fair value option elected other loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	1	9
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2	3
Financing Receivable, Originated Two Years before Latest Fiscal Year	1	1
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	0
Converted to term loans	0	0
Finance receivables and loans, net	4	13
Financing receivables, 60 to 89 days past due | Consumer portfolio segment | Automotive loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	1	66
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	59	165
Financing Receivable, Originated Two Years before Latest Fiscal Year	92	129
Financing Receivable, Originated Three Years before Latest Fiscal Year	67	88
Financing Receivable, Originated Four Years before Latest Fiscal Year	44	55
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	42	32
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	305	535
Financing receivables, 60 to 89 days past due | Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	1
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2	1
Financing Receivable, Originated Two Years before Latest Fiscal Year	1	3
Financing Receivable, Originated Three Years before Latest Fiscal Year	4	2
Financing Receivable, Originated Four Years before Latest Fiscal Year	2	1
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	5	3
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	14	11
Financing receivables, 60 to 89 days past due | Consumer portfolio segment | Mortgage - Legacy
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	2	2
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	2	2
Financing receivables, 60 to 89 days past due | Consumer portfolio segment | Other loan | Excludes fair value option elected other loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	4
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2	1
Financing Receivable, Originated Two Years before Latest Fiscal Year	0	0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0	1
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	0
Converted to term loans	0	0
Finance receivables and loans, net	2	6
Financing receivables, equal to greater than 90 days past due | Consumer portfolio segment | Automotive loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	32
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	34	108
Financing Receivable, Originated Two Years before Latest Fiscal Year	71	96
Financing Receivable, Originated Three Years before Latest Fiscal Year	59	71
Financing Receivable, Originated Four Years before Latest Fiscal Year	42	46
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	50	30
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	256	383
Financing receivables, equal to greater than 90 days past due | Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	1
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1	5
Financing Receivable, Originated Two Years before Latest Fiscal Year	5	8
Financing Receivable, Originated Three Years before Latest Fiscal Year	9	10
Financing Receivable, Originated Four Years before Latest Fiscal Year	4	4
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	25	21
Financing Receivable, Revolving	0	0
Converted to term loans	0	0
Finance receivables and loans, net	44	49
Financing receivables, equal to greater than 90 days past due | Consumer portfolio segment | Mortgage - Legacy
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	17	20
Financing Receivable, Revolving	6	5
Converted to term loans	2	2
Finance receivables and loans, net	25	27
Financing receivables, equal to greater than 90 days past due | Consumer portfolio segment | Other loan | Excludes fair value option elected other loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	0	2
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2	1
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	0
Converted to term loans	0	0
Finance receivables and loans, net	$ 2	$ 3