Finance Receivables - Delinquency (Details) - Retail Finance Receivables [Member] - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
2020	$ 6,098
2019	16,138
2018	10,730
2017	5,747
2016	2,502
2015	1,007
Prior	282
Total	$ 42,504	$ 42,268
Percent of portfolio	100.00%
Total	100.00%
Performing Financial Instruments [Member] | Not Past Due [Member]
Financing Receivable, Past Due [Line Items]
2020	$ 6,078
2019	15,716
2018	10,312
2017	5,412
2016	2,277
2015	877
Prior	214
Current, Total	$ 40,886
Percent of portfolio	96.20%
Nonperforming Financial Instruments [Member]
Financing Receivable, Past Due [Line Items]
2020	$ 20
2019	422
2018	418
2017	335
2016	225
2015	130
Prior	68
Financing receivable past due	$ 1,618
Financing receivable past due (percent)	3.80%
Nonperforming Financial Instruments [Member] | 31 to 60 Days [Member]
Financing Receivable, Past Due [Line Items]
2020	$ 19
2019	302
2018	294
2017	241
2016	161
2015	93
Prior	47
Financing receivable past due	$ 1,157
Financing receivable past due (percent)	2.70%
Nonperforming Financial Instruments [Member] | Greater Than 60 Days [Member]
Financing Receivable, Past Due [Line Items]
2020	$ 1
2019	113
2018	118
2017	90
2016	62
2015	36
Prior	21
Financing receivable past due	$ 441
Financing receivable past due (percent)	1.10%
Nonperforming Financial Instruments [Member] | Financing Receivables, Greater than 30 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
2020	$ 20
2019	415
2018	412
2017	331
2016	223
2015	129
Prior	68
Financing receivable past due	$ 1,598
Financing receivable past due (percent)	3.80%
Nonperforming Financial Instruments [Member] | Financing Receivables, In Repossession [Member]
Financing Receivable, Past Due [Line Items]
2020	$ 0
2019	7
2018	6
2017	4
2016	2
2015	1
Prior	0
Financing receivable past due	$ 20
Financing receivable past due (percent)	0.00%