Condensed Consolidated Financial Information Condensed Consolidated Cash Flow (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ 141,047	$ 198,288	$ 52,372
Cash paid in acquisitions, net of cash received	(212,252)	(336,551)	(269,860)
Proceeds from disposition of franchises, property and equipment	41,581	144,597	102,186
Purchases of property and equipment, including real estate	(120,252)	(150,392)	(102,858)
Payments for (Proceeds from) Other Investing Activities	6,421	(4,705)	1,878
Net Cash Provided by (Used in) Investing Activities	(284,502)	(347,051)	(268,654)
Borrowings on credit facility - floorplan line and other	7,557,237	7,832,014	6,379,328
Repayments On Credit Facility Floorplan Line	(7,504,516)	(7,802,719)	(6,153,677)
Borrowings on Credit Facility Acquisition Line	489,548	389,368	60,000
Repayments on Credit Facility Acquisition Line	(557,696)	(379,681)	0
Borrowings On Real Estate Credit Facility	0	200	19,640
Principal Payments On Real Estate Credit Facility	(3,340)	(9,917)	(8,597)
Net borrowings on 5.25% Senior Unsecured Notes	296,250	0	0
Payments of Debt Issuance Costs	(788)	(1,881)	0
Repayments of 3.00% Convertible Notes	0	(260,074)	0
Proceeds from call options and warrants related to 3.00% Notes	0	32,697	0
Repayments of 2.25% Convertible Notes	0	(182,756)	0
Proceeds from Issuance of Other Long-term Debt	59,855	91,137	10,289
Repayments of Other Long-term Debt	(63,769)	(85,905)	(71,170)
Borrowings Of Long Term Debt Related To Real Estate Loans	32,026	111,979	55,345
Principal Payments Of Long Term Debt Related To Real Estate Loans	(68,739)	(50,033)	(36,978)
Net Issuance of Common and Treasury Shares to Employee Stock Compensation Plans	214	(321)	(1,822)
Repurchases of common stock, amounts based on settlement date	(97,473)	(36,802)	(3,553)
Tax effect from excess stock-based compensation	2,142	1,841	2,993
Dividends paid	(19,942)	(17,097)	(15,805)
Borrowings (repayments) with subsidiaries	0	0	0
Change in investment in subsidiaries	0	0	0
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries	0	0	0
Net cash provided by (used in) financing activities	121,009	171,650	235,993
Effect of Exchange Rate on Cash and Cash Equivalents	(5,492)	(2,127)	(4,146)
Cash and Cash Equivalents, Period Increase (Decrease)	(27,938)	20,760	15,565
Cash and Cash Equivalents, at Carrying Value	13,037	40,975	20,215	$ 4,650
Net borrowings on 5.00% Senior Unsecured Notes	0	539,600	0
Parent Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	93,999	(327)	(3,797)
Cash paid in acquisitions, net of cash received	0	0	0
Proceeds from disposition of franchises, property and equipment	0	0	0
Purchases of property and equipment, including real estate	0	0	0
Payments for (Proceeds from) Other Investing Activities	0	0	0
Net Cash Provided by (Used in) Investing Activities	0	0	0
Borrowings on credit facility - floorplan line and other	0	0	0
Repayments On Credit Facility Floorplan Line	0	0	0
Borrowings on Credit Facility Acquisition Line	489,548	389,368	60,000
Repayments on Credit Facility Acquisition Line	(557,696)	(379,681)
Borrowings On Real Estate Credit Facility		0	0
Principal Payments On Real Estate Credit Facility	0	0	0
Net borrowings on 5.25% Senior Unsecured Notes	296,250
Payments of Debt Issuance Costs	0	(1,881)
Repayments of 3.00% Convertible Notes		(260,074)
Proceeds from call options and warrants related to 3.00% Notes		32,697
Repayments of 2.25% Convertible Notes		(182,756)
Proceeds from Issuance of Other Long-term Debt	0	0	0
Repayments of Other Long-term Debt	0	0	0
Borrowings Of Long Term Debt Related To Real Estate Loans	0	0	0
Principal Payments Of Long Term Debt Related To Real Estate Loans	0	0	0
Net Issuance of Common and Treasury Shares to Employee Stock Compensation Plans	214	(321)	(1,822)
Repurchases of common stock, amounts based on settlement date	(97,473)	(36,802)	(3,553)
Tax effect from excess stock-based compensation	0	0	0
Dividends paid	(19,942)	(17,097)	(15,805)
Borrowings (repayments) with subsidiaries	220,281	78,199	50,651
Change in investment in subsidiaries	(425,181)	(160,925)	(85,674)
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries	0	0	0
Net cash provided by (used in) financing activities	(93,999)	327	3,797
Effect of Exchange Rate on Cash and Cash Equivalents	0	0	0
Cash and Cash Equivalents, Period Increase (Decrease)	0	0	0
Cash and Cash Equivalents, at Carrying Value	0	0	0	0
Net borrowings on 5.00% Senior Unsecured Notes		539,600
Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	49,710	235,236	47,525
Cash paid in acquisitions, net of cash received	(212,252)	(306,364)	(131,654)
Proceeds from disposition of franchises, property and equipment	40,833	141,147	102,069
Purchases of property and equipment, including real estate	(97,009)	(140,407)	(73,615)
Payments for (Proceeds from) Other Investing Activities	6,421	(4,705)	1,878
Net Cash Provided by (Used in) Investing Activities	(262,007)	(310,329)	(101,322)
Borrowings on credit facility - floorplan line and other	7,557,237	7,832,014	6,379,328
Repayments On Credit Facility Floorplan Line	(7,504,516)	(7,802,719)	(6,153,677)
Borrowings on Credit Facility Acquisition Line	0	0	0
Repayments on Credit Facility Acquisition Line	0	0
Borrowings On Real Estate Credit Facility		200	19,640
Principal Payments On Real Estate Credit Facility	(3,340)	(9,917)	(8,597)
Net borrowings on 5.25% Senior Unsecured Notes	0
Payments of Debt Issuance Costs	(788)	0
Repayments of 3.00% Convertible Notes		0
Proceeds from call options and warrants related to 3.00% Notes		0
Repayments of 2.25% Convertible Notes		0
Proceeds from Issuance of Other Long-term Debt	451	0	0
Repayments of Other Long-term Debt	(1,386)	0	0
Borrowings Of Long Term Debt Related To Real Estate Loans	9,596	86,522	27,925
Principal Payments Of Long Term Debt Related To Real Estate Loans	(64,894)	(33,143)	(21,038)
Net Issuance of Common and Treasury Shares to Employee Stock Compensation Plans	0	0	0
Repurchases of common stock, amounts based on settlement date	0	0	0
Tax effect from excess stock-based compensation	2,142	1,841	2,993
Dividends paid	0	0	0
Borrowings (repayments) with subsidiaries	(211,236)	(141,824)	(278,850)
Change in investment in subsidiaries	409,990	161,073	86,038
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries	0	2,119	0
Net cash provided by (used in) financing activities	193,256	96,166	53,762
Effect of Exchange Rate on Cash and Cash Equivalents	0	0	0
Cash and Cash Equivalents, Period Increase (Decrease)	(19,041)	21,073	(35)
Cash and Cash Equivalents, at Carrying Value	6,338	25,379	4,306	4,341
Net borrowings on 5.00% Senior Unsecured Notes		0
Non-Guarantor Subsidiaries [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	(2,662)	(36,621)	8,644
Cash paid in acquisitions, net of cash received	0	(30,187)	(138,206)
Proceeds from disposition of franchises, property and equipment	748	3,450	117
Purchases of property and equipment, including real estate	(23,243)	(9,985)	(29,243)
Payments for (Proceeds from) Other Investing Activities	0	0	0
Net Cash Provided by (Used in) Investing Activities	(22,495)	(36,722)	(167,332)
Borrowings on credit facility - floorplan line and other	0	0	0
Repayments On Credit Facility Floorplan Line	0	0	0
Borrowings on Credit Facility Acquisition Line	0	0	0
Repayments on Credit Facility Acquisition Line	0	0
Borrowings On Real Estate Credit Facility		0	0
Principal Payments On Real Estate Credit Facility	0	0	0
Net borrowings on 5.25% Senior Unsecured Notes	0
Payments of Debt Issuance Costs	0	0
Repayments of 3.00% Convertible Notes		0
Proceeds from call options and warrants related to 3.00% Notes		0
Repayments of 2.25% Convertible Notes		0
Proceeds from Issuance of Other Long-term Debt	59,404	91,137	10,289
Repayments of Other Long-term Debt	(62,383)	(85,905)	(71,170)
Borrowings Of Long Term Debt Related To Real Estate Loans	22,430	25,457	27,420
Principal Payments Of Long Term Debt Related To Real Estate Loans	(3,845)	(16,890)	(15,940)
Net Issuance of Common and Treasury Shares to Employee Stock Compensation Plans	0	0	0
Repurchases of common stock, amounts based on settlement date	0	0	0
Tax effect from excess stock-based compensation	0	0	0
Dividends paid	0	0	0
Borrowings (repayments) with subsidiaries	(9,045)	63,625	228,199
Change in investment in subsidiaries	15,191	(148)	(364)
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries	0	(2,119)	0
Net cash provided by (used in) financing activities	21,752	75,157	178,434
Effect of Exchange Rate on Cash and Cash Equivalents	(5,492)	(2,127)	(4,146)
Cash and Cash Equivalents, Period Increase (Decrease)	(8,897)	(313)	15,600
Cash and Cash Equivalents, at Carrying Value	$ 6,699	15,596	$ 15,909	$ 309
Net borrowings on 5.00% Senior Unsecured Notes		$ 0