Finance Receivables and Loans, Net (Financing Receivable Credit Quality Indicators Consumer) (Details) $ in Millions	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	$ 128,139	$ 128,231	$ 130,055
Consumer portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	8,718
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	29,414
Financing Receivable, Originated Two Years before Latest Fiscal Year	20,348
Financing Receivable, Originated Three Years before Latest Fiscal Year	14,523
Financing Receivable, Originated Four Years before Latest Fiscal Year	7,602
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	8,946
Financing Receivable, Revolving	372
Converted to term loans	133
Finance receivables and loans, net	90,066	89,924
Consumer portfolio segment | Fair value | Finance receivables and loans, net
Financing Receivable, Credit Quality Indicator [Line Items]
Loans receivable, fair value	10	11
Consumer portfolio segment | Excludes fair value option elected other loans
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	90,056	89,913
Consumer portfolio segment | Automotive loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	8,122
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	26,050
Financing Receivable, Originated Two Years before Latest Fiscal Year	17,545
Financing Receivable, Originated Three Years before Latest Fiscal Year	10,999
Financing Receivable, Originated Four Years before Latest Fiscal Year	6,264
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3,852
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	72,832	72,390	71,553
Consumer portfolio segment | Real estate-backed loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	538
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	3,253
Financing Receivable, Originated Two Years before Latest Fiscal Year	2,769
Financing Receivable, Originated Three Years before Latest Fiscal Year	3,515
Financing Receivable, Originated Four Years before Latest Fiscal Year	1,336
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	5,094
Financing Receivable, Revolving	372
Converted to term loans	133
Finance receivables and loans, net	17,010	17,322	$ 17,658
Consumer portfolio segment | Mortgage Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	538
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	3,253
Financing Receivable, Originated Two Years before Latest Fiscal Year	2,769
Financing Receivable, Originated Three Years before Latest Fiscal Year	3,515
Financing Receivable, Originated Four Years before Latest Fiscal Year	1,336
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	4,538
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	15,949	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	556
Financing Receivable, Revolving	372
Converted to term loans	133
Finance receivables and loans, net	1,061	1,141
Consumer portfolio segment | Other loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	58
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	111
Financing Receivable, Originated Two Years before Latest Fiscal Year	34
Financing Receivable, Originated Three Years before Latest Fiscal Year	9
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	224	212
Consumer portfolio segment | Other loan | Excludes fair value option elected other loans
Financing Receivable, Credit Quality Indicator [Line Items]
Finance receivables and loans, net	214	$ 201
Current period | Consumer portfolio segment | Automotive loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	8,101
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	25,291
Financing Receivable, Originated Two Years before Latest Fiscal Year	16,702
Financing Receivable, Originated Three Years before Latest Fiscal Year	10,336
Financing Receivable, Originated Four Years before Latest Fiscal Year	5,784
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3,499
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	69,713
Current period | Consumer portfolio segment | Mortgage Finance operations
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	3,245
Financing Receivable, Originated Two Years before Latest Fiscal Year	2,757
Financing Receivable, Originated Three Years before Latest Fiscal Year	3,498
Financing Receivable, Originated Four Years before Latest Fiscal Year	1,329
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	4,496
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	15,861
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	518
Financing Receivable, Revolving	360
Converted to term loans	130
Finance receivables and loans, net	1,008
Current period | Consumer portfolio segment | Other loan
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Originated in Current Fiscal Year	58
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	108
Financing Receivable, Originated Two Years before Latest Fiscal Year	32
Financing Receivable, Originated Three Years before Latest Fiscal Year	8
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	208
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	20
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	539
Financing Receivable, Originated Two Years before Latest Fiscal Year	563
Financing Receivable, Originated Three Years before Latest Fiscal Year	443
Financing Receivable, Originated Four Years before Latest Fiscal Year	319
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	234
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	2,118
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	2
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	8
Financing Receivable, Originated Two Years before Latest Fiscal Year	8
Financing Receivable, Originated Three Years before Latest Fiscal Year	13
Financing Receivable, Originated Four Years before Latest Fiscal Year	5
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	31
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	67
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	16
Financing Receivable, Revolving	4
Converted to term loans	1
Finance receivables and loans, net	21
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	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1
Financing Receivable, Originated Two Years before Latest Fiscal Year	1
Financing Receivable, Originated Three Years before Latest Fiscal Year	1
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	3
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
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	136
Financing Receivable, Originated Two Years before Latest Fiscal Year	160
Financing Receivable, Originated Three Years before Latest Fiscal Year	125
Financing Receivable, Originated Four Years before Latest Fiscal Year	88
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	63
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	573
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
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	2
Financing Receivable, Originated Three Years before Latest Fiscal Year	1
Financing Receivable, Originated Four Years before Latest Fiscal Year	1
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	6
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	10
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	4
Financing Receivable, Revolving	1
Converted to term loans	1
Finance receivables and loans, net	6
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	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	1
Financing Receivable, Originated Two Years before Latest Fiscal Year	1
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	0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	84
Financing Receivable, Originated Two Years before Latest Fiscal Year	120
Financing Receivable, Originated Three Years before Latest Fiscal Year	95
Financing Receivable, Originated Four Years before Latest Fiscal Year	73
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	56
Financing Receivable, Revolving	0
Converted to term loans	0
Finance receivables and loans, net	428
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	0
Financing Receivable, Originated Two Years before Latest Fiscal Year	2
Financing Receivable, Originated Three Years before Latest Fiscal Year	3
Financing Receivable, Originated Four Years before Latest Fiscal Year	1
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	11
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	18
Financing Receivable, Revolving	7
Converted to term loans	1
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	0
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	$ 1
Operating Segments | Automotive Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Percent of customers electing deferral considered current at time of enrollment	92.00%
Percent of customers electing 120 day deferral	71.00%
Operating Segments | Automotive Finance operations | Consumer portfolio segment
Financing Receivable, Credit Quality Indicator [Line Items]
Customers enrolled in loan program	716,000
Percent of customers enrolling in program	18.00%
Operating Segments | Mortgage Finance operations
Financing Receivable, Credit Quality Indicator [Line Items]
Customers enrolled in loan program	1,200
Percent of customers enrolling in program	3.00%
Percent of customers electing deferral considered current at time of enrollment	92.00%
Corporate and Other
Financing Receivable, Credit Quality Indicator [Line Items]
Customers enrolled in loan program	900
Percent of customers enrolling in program	1.00%