Condensed Consolidated Financial Information Condensed Consolidated Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Income Statements, Captions [Line Items]
REVENUES:	$ 2,860,026	$ 2,518,829
COST OF SALES:	2,440,263	2,135,307
GROSS PROFIT	419,763	383,522
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	324,347	289,779
DEPRECIATION AND AMORTIZATION EXPENSE	16,342	13,606
ASSET IMPAIRMENTS	0
INCOME FROM OPERATIONS	79,074	80,137
Floorplan interest expense	(14,087)	(11,942)
Interest Expense, Other	(18,820)	(16,999)
INCOME BEFORE INCOME TAXES	46,167	51,196
BENEFIT (PROVISION) FOR INCOME TAXES	10,353	17,257
EQUITY IN EARNINGS OF SUBSIDIARIES	0	0
NET INCOME	35,814	33,939
COMPREHENSIVE LOSS	17,276	6,795
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO PARENT	53,090	40,734
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
REVENUES:	0	0
COST OF SALES:	0	0
GROSS PROFIT	0	0
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	1,768	1,966
DEPRECIATION AND AMORTIZATION EXPENSE	0	0
ASSET IMPAIRMENTS	0
INCOME FROM OPERATIONS	(1,768)	(1,966)
Floorplan interest expense	0	0
Interest Expense, Other	0	0
INCOME BEFORE INCOME TAXES	(1,768)	(1,966)
BENEFIT (PROVISION) FOR INCOME TAXES	(424)	737
EQUITY IN EARNINGS OF SUBSIDIARIES	37,158	35,167
NET INCOME	35,814	33,938
COMPREHENSIVE LOSS	0	0
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO PARENT	35,814	33,938
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
REVENUES:	2,088,487	1,967,718
COST OF SALES:	1,752,802	1,647,123
GROSS PROFIT	335,685	320,595
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	249,165	232,611
DEPRECIATION AND AMORTIZATION EXPENSE	12,881	11,567
ASSET IMPAIRMENTS	0
INCOME FROM OPERATIONS	73,639	76,417
Floorplan interest expense	(12,337)	(10,878)
Interest Expense, Other	(17,017)	16,274
INCOME BEFORE INCOME TAXES	44,285	49,265
BENEFIT (PROVISION) FOR INCOME TAXES	9,780	(17,084)
EQUITY IN EARNINGS OF SUBSIDIARIES	0	0
NET INCOME	34,505	32,181
COMPREHENSIVE LOSS	9,405	2,658
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO PARENT	43,910	34,839
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
REVENUES:	771,539	551,111
COST OF SALES:	687,461	488,184
GROSS PROFIT	84,078	62,927
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	73,414	55,202
DEPRECIATION AND AMORTIZATION EXPENSE	3,461	2,039
ASSET IMPAIRMENTS	0
INCOME FROM OPERATIONS	7,203	5,686
Floorplan interest expense	(1,750)	(1,064)
Interest Expense, Other	(1,803)	725
INCOME BEFORE INCOME TAXES	3,650	3,897
BENEFIT (PROVISION) FOR INCOME TAXES	997	(910)
EQUITY IN EARNINGS OF SUBSIDIARIES	0	0
NET INCOME	2,653	2,987
COMPREHENSIVE LOSS	7,871	4,137
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO PARENT	10,524	7,124
Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
REVENUES:	0	0
COST OF SALES:	0	0
GROSS PROFIT	0	0
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	0	0
DEPRECIATION AND AMORTIZATION EXPENSE	0	0
ASSET IMPAIRMENTS	0
INCOME FROM OPERATIONS	0	0
Floorplan interest expense	0	0
Interest Expense, Other	0	0
INCOME BEFORE INCOME TAXES	0	0
BENEFIT (PROVISION) FOR INCOME TAXES	0	0
EQUITY IN EARNINGS OF SUBSIDIARIES	(37,158)	(35,167)
NET INCOME	(37,158)	(35,167)
COMPREHENSIVE LOSS	0	0
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO PARENT	$ (37,158)	$ (35,167)