Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net income	$ 65,581	$ 230,692	$ 198,476
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	49,322	31,545	24,695
Equity-based compensation	14,088	5,109	1,597
Loss on debt restructure	1,676	462	5,052
Goodwill impairment	40,046
Loss (gain) on sale of assets	2,810	(133)	(564)
Provision for losses on accounts receivable	2,444	839	1,332
Accretion of original debt issuance discount	1,034	942	1,127
Non-cash interest	5,068	4,360	4,543
Deferred income taxes	11,364	130,966	3,658
Tax Receivable Agreement liability adjustment	1,324	(100,758)
Change in assets and liabilities, net of acquisitions:
Receivables and contracts in transit	(16,550)	(38,019)	(10,932)
Inventories	(99,610)	(342,780)	(30,964)
Prepaid expenses and other assets	(8,290)	(20,244)	(4,625)
Checks in excess of bank balance	3,942	6,585	(7,478)
Accounts payable and other accrued expenses	45,230	52,155	13,915
Payment pursuant to Tax Receivable Agreement	(8,914)	(203)
Accrued rent for cease-use locations	(488)	(91)	945
Deferred revenue and gains	12,448	12,943	6,143
Other, net	13,767	9,315	8,855
Net cash provided by (used in) operating activities	136,292	(16,315)	215,775
Investing activities
Purchases of property and equipment	(133,557)	(59,559)	(39,866)
Purchase of real property	(120,802)	(21,212)	(17,077)
Proceeds from the sale of real property	56,932	6,000	15,892
Purchases of businesses, net of cash acquired	(99,240)	(392,956)	(78,606)
Proceeds from sale of property and equipment	3,978	795	3,870
Purchase of intangible assets		(1,523)
Net cash used in investing activities	(292,689)	(468,455)	(115,787)
Financing activities
Proceeds from long-term debt	329,775	299,246	188,137
Payments on long-term debt	(82,820)	(7,916)	(288,520)
Net (payments) borrowings on notes payable - floor plan, net	(85,446)	358,478	34,785
Borrowings on revolving line of credit	45,164		12,000
Payments on revolver	(6,425)		(12,000)
Payments of principal on capital lease obligations	(844)	(1,198)	(1,465)
Payments of principal on right to use liability	(161)	(150)	(200)
Payment of debt issuance costs	(3,345)	(4,604)	(7,085)
Dividends on Class A common stock	(22,697)	(22,241)	(1,515)
Proceeds from exercise of stock options	153	1,728
RSU shares withheld for tax	(1,365)	(368)
Disgorgement of short-swing profits by Section 16 officer	557
Members' distributions	(101,755)	(149,633)	(236,145)
Net cash (used in) provided by financing activities	70,791	594,737	(77,817)
Increase (decrease) in cash and cash equivalents	(85,606)	109,967	22,171
Cash and cash equivalents at beginning of the period	224,163	114,196	92,025
Cash and cash equivalents at end of period	138,557	224,163	114,196
Class A common stock
Operating activities
Net income	$ 65,581	230,692	11,113
Financing activities
Proceeds from issuance of Class A common stock sold in an initial public offering net of underwriter discounts and commissions			234,185
Proceeds from issuance of Class A common stock sold in a public offering net of underwriter discounts, commissions and offering expenses		$ 121,395	$ 6