Commitments and Contingencies (Details Textual) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) dealerships
Manufacturer [Line Items]
Payments for Legal Settlements	$ 1,210
Volkswagen legal claims	$ 14,700
Number of Volkswagen dealers	652
Proceeds from Legal Settlements	$ 0
Volkswagen [Member]
Manufacturer [Line Items]
New vehicle retail unit sales	2.60%
Number Of Dealerships | dealerships	7
TotalNumberOfInstallments	18
NumberOfInstallmentsReceived	11,000