Consolidated Balance Sheets - USD ($)	Dec. 31, 2017	Dec. 31, 2016
CURRENT ASSETS:
Cash and cash equivalents	$ 28,787,000	$ 20,992,000
Contracts-in-transit and vehicle receivables, net	306,433,000	269,508,000
Accounts and notes receivable, net	188,611,000	173,364,000
Inventories, net	1,763,293,000	1,651,815,000
Prepaid expenses and other current assets	42,062,000	34,908,000
Total current assets	2,329,186,000	2,150,587,000
PROPERTY AND EQUIPMENT, net	1,318,959,000	1,125,883,000
GOODWILL	913,034,000	876,763,000
INTANGIBLE FRANCHISE RIGHTS	285,632,000	284,876,000
Investment in Subsidiaries	0	0
OTHER ASSETS	24,254,000	23,794,000
Total assets	4,871,065,000	4,461,903,000
CURRENT LIABILITIES:
Floorplan notes payable - credit facility and other	1,240,695,000	1,136,654,000
Offset account related to floorplan notes payable - credit facility	(86,547,000)	(59,626,000)
Floorplan notes payable — manufacturer affiliates	397,183,000	392,661,000
Offset account related to floorplan notes payable - manufacturer affiliates	(22,500,000)	(25,500,000)
Current maturities of long-term debt	77,609,000	72,419,000
Derivative Liability, Current	1,996,000	3,941,000
Accounts payable	412,981,000	356,099,000
Accrued expenses	177,070,000	176,469,000
Total current liabilities	2,198,487,000	2,053,117,000
LONG-TERM DEBT, net of current maturities	1,318,184,000	1,212,809,000
Deferred Tax Liabilities, Net, Noncurrent	124,404,000	161,502,000
LIABILITIES FROM INTEREST RATE RISK MANAGEMENT ACTIVITIES	8,583,000	20,470,000
Other Liabilities, Noncurrent	97,125,000	83,805,000
Commitments and Contingencies	0
Stockholders' Equity Attributable to Parent [Abstract]
Preferred Stock, Value, Issued	0	0
Common Stock, Value, Issued	255,000	257,000
Additional Paid in Capital, Common Stock	291,461,000	290,899,000
Retained Earnings (Accumulated Deficit)	1,246,323,000	1,053,301,000
Accumulated Other Comprehensive Income (Loss), Net of Tax	(123,226,000)	(146,944,000)
Treasury Stock, Value	(290,531,000)	(267,313,000)
Stockholders' Equity Attributable	1,124,282,000	930,200,000
Total liabilities and stockholders' equity	4,871,065,000	4,461,903,000
Consolidation, Eliminations [Member]
CURRENT ASSETS:
Cash and cash equivalents	0	0
Contracts-in-transit and vehicle receivables, net	0	0
Accounts and notes receivable, net	0	0
Inventories, net	0	0
Prepaid expenses and other current assets	0	0
Total current assets	(39,936,000)	(8,929,000)
PROPERTY AND EQUIPMENT, net	0	0
GOODWILL	0	0
INTANGIBLE FRANCHISE RIGHTS	0	0
Investment in Subsidiaries	(2,999,407,000)	(2,787,328,000)
OTHER ASSETS	0	0
Total assets	(3,039,343,000)	(2,796,257,000)
CURRENT LIABILITIES:
Floorplan notes payable - credit facility and other	0	0
Offset account related to floorplan notes payable - credit facility	0	0
Floorplan notes payable — manufacturer affiliates	0	0
Offset account related to floorplan notes payable - manufacturer affiliates	0	0
Current maturities of long-term debt	0	0
Derivative Liability, Current	0	0
Accounts payable	0	0
Accrued expenses	0	0
Total current liabilities	(930,931,000)	(884,591,000)
LONG-TERM DEBT, net of current maturities	0	0
LIABILITIES FROM INTEREST RATE RISK MANAGEMENT ACTIVITIES	0	0
Stockholders' Equity Attributable to Parent [Abstract]
Stockholders' Equity Attributable	(2,999,407,000)	(2,787,328,000)
Total liabilities and stockholders' equity	(3,039,343,000)	(2,796,257,000)
Parent Company [Member]
CURRENT ASSETS:
Cash and cash equivalents	0	0
Contracts-in-transit and vehicle receivables, net	0	0
Accounts and notes receivable, net	0	0
Inventories, net	0	0
Prepaid expenses and other current assets	1,934,000	516,000
Total current assets	28,922,000	516,000
PROPERTY AND EQUIPMENT, net	0	0
GOODWILL	0	0
INTANGIBLE FRANCHISE RIGHTS	0	0
Investment in Subsidiaries	2,999,407,000	2,787,328,000
OTHER ASSETS	0	0
Total assets	3,028,329,000	2,787,844,000
CURRENT LIABILITIES:
Floorplan notes payable - credit facility and other	0	0
Offset account related to floorplan notes payable - credit facility	0	0
Floorplan notes payable — manufacturer affiliates	0	0
Offset account related to floorplan notes payable - manufacturer affiliates	0	0
Current maturities of long-term debt	24,741,000	0
Derivative Liability, Current	0	0
Accounts payable	0	0
Accrued expenses	0	0
Total current liabilities	915,736,000	875,662,000
LONG-TERM DEBT, net of current maturities	865,202,000	836,056,000
LIABILITIES FROM INTEREST RATE RISK MANAGEMENT ACTIVITIES	0	0
Stockholders' Equity Attributable to Parent [Abstract]
Stockholders' Equity Attributable	1,247,508,000	1,077,146,000
Total liabilities and stockholders' equity	$ 3,028,329,000	$ 2,787,844,000