Finance Receivables - Credit Risk Profile by Dealer (Details) - Commercial Finance Receivables [Member] - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving	$ 7,382
2020	401
2019	214
2018	133
2017	130
2016	117
2015	62
Prior	22
Total	$ 8,461	$ 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	$ 6,723
2020	400
2019	198
2018	92
2017	113
2016	93
2015	44
Prior	0
Total	$ 7,663
Percent of portfolio	90.60%
Group II - Performing accounts experiencing potential weakness in financial metrics [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving	$ 428
2020	1
2019	7
2018	12
2017	15
2016	13
2015	13
Prior	22
Total	$ 511
Percent of portfolio	6.00%
Group III - Non-Performing accounts with inadequate paying capacity for current obligations [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving	$ 227
2020	0
2019	9
2018	29
2017	2
2016	11
2015	1
Prior	0
Total	$ 279
Percent of portfolio	3.30%
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	$ 4
2020	0
2019	0
2018	0
2017	0
2016	0
2015	4
Prior	0
Total	$ 8
Percent of portfolio	0.10%