Property and Equipment (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property Plant and Equipment (Textual) [Abstract]
Asset impairment charges of property and equipment	$ 200	$ 2,800
Capital expenditures incurred for purchase and construction of assets	98,300	100,600
Capital Expenditures Incurred but Not yet Paid	8,759	15,930	$ 32,720
Depreciation and amortization	57,900	51,200	$ 47,200
Building recorded under capital lease included in property plant equipment before accumulated depreciation	77,400	68,900
Land and Building [Member]
Property Plant and Equipment (Textual) [Abstract]
Acquisition of fixed assets	110,400	28,800
Dealership Acquisitions [Member]
Property Plant and Equipment (Textual) [Abstract]
Acquisition of fixed assets		$ 39,100
Dealership Acquisitions [Member] | Land and Building [Member]
Property Plant and Equipment (Textual) [Abstract]
Acquisition of fixed assets	$ 29,000