Acquisitions - Assets (Liabilities) Acquired (Assumed) at Fair Value (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Assets (liabilities) acquired (assumed) at fair value:
Goodwill	$ 383,676		$ 359,117
Cash paid for acquisition, net of cash acquired	38,608	$ 80,203
2019 Acquisitions
Assets (liabilities) acquired (assumed) at fair value:
Inventory, net	13,895
Prepaid expenses and other assets	96
Property and equipment, net	158
Accounts payable and accrued liabilities	(62)
Other liabilities	(38)
Total tangible net assets acquired	14,049
Goodwill	24,559
Purchase Price	38,608
Cash paid for acquisition, net of cash acquired	38,608
Inventory purchases financed via floor plan	(8,416)
Cash payment net of floor plan financing	$ 30,192
2018 Acquisitions
Assets (liabilities) acquired (assumed) at fair value:
Cash and cash equivalents		2,648
Contracts in Transit		102
Accounts receivable, net		102
Inventory, net		40,150
Prepaid expenses and other assets		98
Property and equipment, net		709
Other assets		48
Accounts payable and accrued liabilities		(1,070)
Other liabilities		(412)
Total tangible net assets acquired		42,375
Intangible assets acquired		318
Goodwill		40,158
Purchase Price		82,851
Cash and cash equivalents acquired		(2,648)
Cash paid for acquisition, net of cash acquired		80,203
Inventory purchases financed via floor plan		(29,365)
Cash payment net of floor plan financing		50,838
2018 Acquisitions | Trademarks and trade names
Assets (liabilities) acquired (assumed) at fair value:
Intangible assets acquired		$ 318
Estimated Life (in years)		15 years