Finance Receivables - Credit Risk Profile by Dealer (Details) - Commercial Finance Receivables [Member] - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving	$ 11,322
2020	101
2019	270
2018	146
2017	175
2016	141
2015	95
Prior	32
Total	$ 12,282	$ 12,149
Percent of portfolio	100.00%
Floorplan Advances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of revolving balance	98.00%
Group I - Performing accounts with strong to acceptable financial metrics [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving	$ 10,351
2020	101
2019	253
2018	124
2017	128
2016	118
2015	77
Prior	9
Total	$ 11,161
Percent of portfolio	90.90%
Group II - Performing accounts experiencing potential weakness in financial metrics [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving	$ 632
2020	0
2019	9
2018	12
2017	33
2016	23
2015	13
Prior	23
Total	$ 745
Percent of portfolio	6.10%
Group III - Non-Performing accounts with inadequate paying capacity for current obligations [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving	$ 325
2020	0
2019	8
2018	10
2017	14
2016	0
2015	1
Prior	0
Total	$ 358
Percent of portfolio	2.90%
Group IV - Non-Performing accounts with inadequate paying capacity for current obligations and inherent weaknesses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving	$ 14
2020	0
2019	0
2018	0
2017	0
2016	0
2015	4
Prior	0
Total	$ 18
Percent of portfolio	0.10%