Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators Consumer) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	$ 118,028	$ 128,231	$ 128,609
Consumer portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	90,160	89,924
Consumer portfolio segment | Excludes fair value option elected other loans
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	24,513
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	24,966
Financing Receivable, Originated Two Years before Latest Fiscal Year	16,443
Financing Receivable, Originated Three Years before Latest Fiscal Year	11,287
Financing Receivable, Originated Four Years before Latest Fiscal Year	5,857
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	6,710
Financing Receivable, Revolving	272
Converted to term loans	104
Finance receivables and loans, net	90,152	89,913
Consumer portfolio segment | Automotive loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	21,421
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	22,101
Financing Receivable, Originated Two Years before Latest Fiscal Year	14,384
Financing Receivable, Originated Three Years before Latest Fiscal Year	8,649
Financing Receivable, Originated Four Years before Latest Fiscal Year	4,705
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	2,501
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	73,761	72,390	73,071
Consumer portfolio segment | Real estate-backed loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	2,872
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2,789
Financing Receivable, Originated Two Years before Latest Fiscal Year	2,042
Financing Receivable, Originated Three Years before Latest Fiscal Year	2,633
Financing Receivable, Originated Four Years before Latest Fiscal Year	1,151
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	4,209
Financing Receivable, Revolving	272
Converted to term loans	104
Finance receivables and loans, net	16,072	17,322	$ 17,010
Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	2,872
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2,789
Financing Receivable, Originated Two Years before Latest Fiscal Year	2,042
Financing Receivable, Originated Three Years before Latest Fiscal Year	2,633
Financing Receivable, Originated Four Years before Latest Fiscal Year	1,151
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3,678
Financing Receivable, Revolving	0
Converted to term loans	3
Finance receivables and loans, net	15,168	16,181
Consumer portfolio segment | Mortgage - Legacy
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	531
Financing Receivable, Revolving	272
Converted to term loans	101
Finance receivables and loans, net	904	1,141
Consumer portfolio segment | Other loan
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	327	212
Loans receivable, fair value	8	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	220
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	76
Financing Receivable, Originated Two Years before Latest Fiscal Year	17
Financing Receivable, Originated Three Years before Latest Fiscal Year	5
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
Converted to term loans	0
Finance receivables and loans, net	319	$ 201
Current period | Consumer portfolio segment | Automotive loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	21,216
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	21,433
Financing Receivable, Originated Two Years before Latest Fiscal Year	13,802
Financing Receivable, Originated Three Years before Latest Fiscal Year	8,233
Financing Receivable, Originated Four Years before Latest Fiscal Year	4,433
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	2,327
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	71,444
Current period | Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	2,811
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	2,758
Financing Receivable, Originated Two Years before Latest Fiscal Year	2,014
Financing Receivable, Originated Three Years before Latest Fiscal Year	2,609
Financing Receivable, Originated Four Years before Latest Fiscal Year	1,141
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3,629
Financing Receivable, Revolving	0
Converted to term loans	3
Finance receivables and loans, net	14,965
Current period | Consumer portfolio segment | Mortgage - Legacy
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	498
Financing Receivable, Revolving	265
Converted to term loans	99
Finance receivables and loans, net	862
Current period | Consumer portfolio segment | Other loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	216
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	73
Financing Receivable, Originated Two Years before Latest Fiscal Year	17
Financing Receivable, Originated Three Years before Latest Fiscal Year	5
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
Converted to term loans	0
Finance receivables and loans, net	312
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	156
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	435
Financing Receivable, Originated Two Years before Latest Fiscal Year	366
Financing Receivable, Originated Three Years before Latest Fiscal Year	261
Financing Receivable, Originated Four Years before Latest Fiscal Year	171
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	106
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	1,495
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	56
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	29
Financing Receivable, Originated Two Years before Latest Fiscal Year	18
Financing Receivable, Originated Three Years before Latest Fiscal Year	14
Financing Receivable, Originated Four Years before Latest Fiscal Year	7
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	33
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	157
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
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	9
Financing Receivable, Revolving	2
Converted to term loans	0
Finance receivables and loans, net	11
Financing receivables, 30 to 59 days past due | Consumer portfolio segment | Other loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	2
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	0
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	4
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	34
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	131
Financing Receivable, Originated Two Years before Latest Fiscal Year	111
Financing Receivable, Originated Three Years before Latest Fiscal Year	77
Financing Receivable, Originated Four Years before Latest Fiscal Year	47
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	30
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	430
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	5
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1
Financing Receivable, Originated Two Years before Latest Fiscal Year	5
Financing Receivable, Originated Three Years before Latest Fiscal Year	4
Financing Receivable, Originated Four Years before Latest Fiscal Year	0
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	18
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
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	5
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	5
Financing receivables, 60 to 89 days past due | Consumer portfolio segment | Other loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	1
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1
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	0
Converted to term loans	0
Finance receivables and loans, net	2
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	15
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	102
Financing Receivable, Originated Two Years before Latest Fiscal Year	105
Financing Receivable, Originated Three Years before Latest Fiscal Year	78
Financing Receivable, Originated Four Years before Latest Fiscal Year	54
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	38
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	392
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
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1
Financing Receivable, Originated Two Years before Latest Fiscal Year	5
Financing Receivable, Originated Three Years before Latest Fiscal Year	6
Financing Receivable, Originated Four Years before Latest Fiscal Year	3
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	13
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	28
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
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	19
Financing Receivable, Revolving	5
Converted to term loans	2
Finance receivables and loans, net	26
Financing receivables, equal to greater than 90 days past due | Consumer portfolio segment | Other loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	1
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	0
Converted to term loans	0
Finance receivables and loans, net	$ 1