Condensed Consolidated Financial Information Condensed Consolidated Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
REVENUES:	$ 2,920,405	$ 3,012,292	$ 2,672,195	$ 2,518,829	$ 2,673,632	$ 2,823,176	$ 2,782,449	$ 2,608,355	$ 11,123,721	$ 10,887,612	$ 10,632,505
COST OF SALES:									9,478,212	9,292,543	9,098,533
GROSS PROFIT	425,675	431,420	$ 404,892	$ 383,522	389,181	406,668	410,119	389,101	1,645,509	1,595,069	1,533,972
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES									1,226,195	1,170,763	1,120,833
Depreciation and amortization									57,936	51,234	47,239
ASSET IMPAIRMENTS	$ 10,000	$ 9,500			$ 20,000	$ 10,900	$ 1,000	$ 900	19,506	32,838	87,562
INCOME (LOSS) FROM OPERATIONS									341,872	340,234	278,338
Floorplan interest expense									(52,372)	(44,927)	(39,264)
Interest Expense, Other									(70,497)	(67,936)	(56,903)
INCOME (LOSS) BEFORE INCOME TAXES AND EQUITY IN EARNINGS OF SUBSIDIARIES									219,003	227,371	182,171
BENEFIT (PROVISION) FOR INCOME TAXES									(5,561)	(80,306)	(88,172)
EQUITY IN EARNINGS OF SUBSIDIARIES									0	0	0
NET INCOME									213,442	147,065	93,999
COMPREHENSIVE INCOME (LOSS)									23,718	(8,960)	(56,000)
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO PARENT									237,160	138,105	37,999
Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
REVENUES:									0	0	0
COST OF SALES:									0	0	0
GROSS PROFIT									0	0	0
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES									0	0	0
Depreciation and amortization									0	0	0
ASSET IMPAIRMENTS									0	0	0
INCOME (LOSS) FROM OPERATIONS									0	0	0
Floorplan interest expense									0	0	0
Interest Expense, Other									0	0	0
INCOME (LOSS) BEFORE INCOME TAXES AND EQUITY IN EARNINGS OF SUBSIDIARIES									0	0	0
BENEFIT (PROVISION) FOR INCOME TAXES									0	0	0
EQUITY IN EARNINGS OF SUBSIDIARIES									(215,556)	(148,767)	(94,439)
NET INCOME									(215,556)	(148,767)	(94,439)
COMPREHENSIVE INCOME (LOSS)									0		0
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO PARENT									(215,556)	(148,767)	(94,439)
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
REVENUES:									0	0	0
COST OF SALES:									0	0	0
GROSS PROFIT									0	0	0
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES									3,381	2,722	3,024
Depreciation and amortization									0	0	0
ASSET IMPAIRMENTS									0	0	0
INCOME (LOSS) FROM OPERATIONS									(3,381)	(2,722)	(3,024)
Floorplan interest expense									0	0	0
Interest Expense, Other									0	0	2,320
INCOME (LOSS) BEFORE INCOME TAXES AND EQUITY IN EARNINGS OF SUBSIDIARIES									(3,381)	(2,722)	(704)
BENEFIT (PROVISION) FOR INCOME TAXES									1,268	1,020	264
EQUITY IN EARNINGS OF SUBSIDIARIES									215,556	148,767	94,439
NET INCOME									213,443	147,065	93,999
COMPREHENSIVE INCOME (LOSS)									0		0
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO PARENT									213,443	147,065	93,999
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
REVENUES:									8,680,565	8,734,673	8,893,990
COST OF SALES:									7,315,252	7,379,323	7,555,043
GROSS PROFIT									1,365,313	1,355,350	1,338,947
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES									974,413	954,495	950,268
Depreciation and amortization									48,284	43,472	41,220
ASSET IMPAIRMENTS									12,762	21,794	18,899
INCOME (LOSS) FROM OPERATIONS									329,854	335,589	328,560
Floorplan interest expense									(47,222)	(40,444)	(36,063)
Interest Expense, Other									(66,490)	(64,870)	(52,276)
INCOME (LOSS) BEFORE INCOME TAXES AND EQUITY IN EARNINGS OF SUBSIDIARIES									216,142	230,275	240,221
BENEFIT (PROVISION) FOR INCOME TAXES									(6,947)	(83,560)	(89,698)
EQUITY IN EARNINGS OF SUBSIDIARIES									0	0	0
NET INCOME									209,195	146,715	150,523
COMPREHENSIVE INCOME (LOSS)									8,657	10,121	(1,543)
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO PARENT									217,852	156,836	148,980
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
REVENUES:									2,443,156	2,152,939	1,738,515
COST OF SALES:									2,162,960	1,913,220	1,543,490
GROSS PROFIT									280,196	239,719	195,025
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES									248,401	213,546	167,541
Depreciation and amortization									9,652	7,762	6,019
ASSET IMPAIRMENTS									6,744	11,044	68,663
INCOME (LOSS) FROM OPERATIONS									15,399	7,367	(47,198)
Floorplan interest expense									(5,150)	(4,483)	(3,201)
Interest Expense, Other									(4,007)	(3,066)	(6,947)
INCOME (LOSS) BEFORE INCOME TAXES AND EQUITY IN EARNINGS OF SUBSIDIARIES									6,242	(182)	(57,346)
BENEFIT (PROVISION) FOR INCOME TAXES									118	2,234	1,262
EQUITY IN EARNINGS OF SUBSIDIARIES									0	0	0
NET INCOME									6,360	2,052	(56,084)
COMPREHENSIVE INCOME (LOSS)									15,061	(19,081)	(54,457)
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO PARENT									$ 21,421	$ (17,029)	$ (110,541)