Condensed Consolidated Financial Information Condensed Consolidated Cash Flow (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	$ 54,685	$ 172,867
Cash paid in acquisitions, net of cash received	(95)	(54,739)
Proceeds from disposition of franchises, property and equipment	2,582	13,985
Purchases of property and equipment, including real estate	(67,266)	(70,272)
Payments for (Proceeds from) Deposits on Real Estate Acquisitions	(57,099)	(193)
Other	2,074	3,349
Net cash used in investing activities	(119,804)	(107,870)
Borrowings on credit facility - floorplan line and other	3,369,580	3,373,126
Repayments on credit facility - floorplan line and other	(3,288,367)	(3,325,917)
Borrowings on credit facility - acquisition line	47,509	150,020
Repayments on credit facility - acquisition line	(15,000)	(140,020)
Borrowings on other debt	5,137	19,653
Principal payments on other debt	(542)	(22,248)
Borrowings Of Long Term Debt Related To Real Estate Loans, Net of Debt Issue Costs	12,901	30,754
Principal payments on debt related to real estate	(13,897)	(12,215)
Net Issuance of Common and Treasury Shares to Employee Stock Compensation Plans	2,487	136
Repurchases of common stock, amounts based on settlement date	(39,025)	(115,246)
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net	0	(85)
Dividends paid	(10,200)	(10,124)
Proceeds from (Payments for) Other Financing Activities	0	(3,159)
Borrowings (repayments) with subsidiaries	0	0
Investment in subsidiaries	0	0
Net cash provided by (used in) financing activities	70,583	(55,325)
Effect of Exchange Rate on Cash and Cash Equivalents	117	2,256
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	5,581	11,928
CASH AND CASH EQUIVALENTS, beginning of period	20,992	13,037
CASH AND CASH EQUIVALENTS, end of period	26,573	24,965
Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	73,072	80,872
Cash paid in acquisitions, net of cash received	0	0
Proceeds from disposition of franchises, property and equipment	0	0
Purchases of property and equipment, including real estate	0	0
Payments for (Proceeds from) Deposits on Real Estate Acquisitions	0	0
Other	0	0
Net cash used in investing activities	0	0
Borrowings on credit facility - floorplan line and other	0	0
Repayments on credit facility - floorplan line and other	0	0
Borrowings on credit facility - acquisition line	47,509	150,020
Repayments on credit facility - acquisition line	(15,000)	(140,020)
Borrowings on other debt	0	0
Principal payments on other debt	0	0
Borrowings Of Long Term Debt Related To Real Estate Loans, Net of Debt Issue Costs	0	0
Principal payments on debt related to real estate	0	0
Net Issuance of Common and Treasury Shares to Employee Stock Compensation Plans	2,487	136
Repurchases of common stock, amounts based on settlement date	(39,025)	(115,246)
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net		(85)
Dividends paid	(10,200)	(10,124)
Proceeds from (Payments for) Other Financing Activities		(2,736)
Borrowings (repayments) with subsidiaries	32,214	233,120
Investment in subsidiaries	(91,057)	(195,937)
Net cash provided by (used in) financing activities	(73,072)	(80,872)
Effect of Exchange Rate on Cash and Cash Equivalents	0	0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	0	0
CASH AND CASH EQUIVALENTS, beginning of period	0	0
CASH AND CASH EQUIVALENTS, end of period	0	0
Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(32,554)	88,538
Cash paid in acquisitions, net of cash received	0	0
Proceeds from disposition of franchises, property and equipment	265	12,728
Purchases of property and equipment, including real estate	(60,594)	(59,894)
Payments for (Proceeds from) Deposits on Real Estate Acquisitions	273	193
Other	2,074	3,200
Net cash used in investing activities	(57,982)	(44,159)
Borrowings on credit facility - floorplan line and other	3,319,971	3,373,126
Repayments on credit facility - floorplan line and other	(3,244,979)	(3,325,917)
Borrowings on credit facility - acquisition line	0	0
Repayments on credit facility - acquisition line	0	0
Borrowings on other debt	0	0
Principal payments on other debt	(542)	(461)
Borrowings Of Long Term Debt Related To Real Estate Loans, Net of Debt Issue Costs		30,754
Principal payments on debt related to real estate	(11,183)	(9,611)
Net Issuance of Common and Treasury Shares to Employee Stock Compensation Plans	0	0
Repurchases of common stock, amounts based on settlement date	0	0
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net		0
Dividends paid	0	0
Proceeds from (Payments for) Other Financing Activities		(423)
Borrowings (repayments) with subsidiaries	(65,909)	(236,314)
Investment in subsidiaries	91,017	123,624
Net cash provided by (used in) financing activities	88,375	(45,222)
Effect of Exchange Rate on Cash and Cash Equivalents	0	0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(2,161)	(843)
CASH AND CASH EQUIVALENTS, beginning of period	8,039	6,338
CASH AND CASH EQUIVALENTS, end of period	5,878	5,495
Non-Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	14,167	3,457
Cash paid in acquisitions, net of cash received	(95)	(54,739)
Proceeds from disposition of franchises, property and equipment	2,317	1,257
Purchases of property and equipment, including real estate	(6,672)	(10,378)
Payments for (Proceeds from) Deposits on Real Estate Acquisitions	(57,372)	0
Other	0	149
Net cash used in investing activities	(61,822)	(63,711)
Borrowings on credit facility - floorplan line and other	49,609	0
Repayments on credit facility - floorplan line and other	(43,388)	0
Borrowings on credit facility - acquisition line	0	0
Repayments on credit facility - acquisition line	0	0
Borrowings on other debt	5,137	19,653
Principal payments on other debt	0	(21,787)
Borrowings Of Long Term Debt Related To Real Estate Loans, Net of Debt Issue Costs	12,901	0
Principal payments on debt related to real estate	(2,714)	(2,604)
Net Issuance of Common and Treasury Shares to Employee Stock Compensation Plans	0	0
Repurchases of common stock, amounts based on settlement date	0	0
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net		0
Dividends paid	0	0
Proceeds from (Payments for) Other Financing Activities		0
Borrowings (repayments) with subsidiaries	33,695	3,194
Investment in subsidiaries	40	72,313
Net cash provided by (used in) financing activities	55,280	70,769
Effect of Exchange Rate on Cash and Cash Equivalents	117	2,256
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	7,742	12,771
CASH AND CASH EQUIVALENTS, beginning of period	12,953	6,699
CASH AND CASH EQUIVALENTS, end of period	$ 20,695	$ 19,470