Acquisitions - Purchase Price (Details) - Assets Or Stock Of Multiple Dealership Locations Acquired - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Acquisitions
Purchase Price	$ 75,448	$ 60,251
Inventory purchases financed via floor plan	(16,805)	(22,265)
Cash payment net of holdback and floor plan financing	58,643	37,986
Goodwill for tax purposes	$ 45,800	$ 33,500