Segment Information Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
New vehicle retail sales									$ 6,001,306	$ 5,741,619	$ 5,224,921
Used vehicle retail sales									2,638,969	2,324,868	2,039,428
Used vehicle wholesale sales									397,251	379,143	332,185
Parts and service									1,186,193	1,125,694	1,010,685
Finance and insurance									408,786	366,565	311,362
Total revenues	$ 2,672,602	$ 2,800,569	$ 2,726,480	$ 2,432,854	$ 2,538,940	$ 2,626,448	$ 2,511,638	$ 2,260,863	10,632,505	9,937,889	8,918,581
Gross profit	380,133	398,382	391,573	$ 363,884	365,959	374,709	369,148	$ 338,122	1,533,972	1,447,938	1,292,546
Selling, general and administrative expense									1,120,833	1,061,964	976,856
Depreciation and amortization									47,239	42,344	35,826
ASSET IMPAIRMENTS	85,700	$ 900	$ 1,000		30,400	9,400	1,700		87,562	41,520	6,542
Floorplan interest expense									(39,264)	(41,614)	(41,667)
Other interest expense, net									(56,903)	(49,693)	(38,971)
Other Expenses									0	0	(789)
Gains (Losses) on Extinguishment of Debt									0	(46,403)	0
Income before income taxes									182,171	164,400	191,895
Provision for income taxes									(88,172)	(71,396)	(77,903)
Net income									93,999	93,004	113,992
Capital expenditures									107,232	97,709	69,216
Total assets	4,414,929				4,141,492				4,414,929	4,141,492
U.S. [Member]
Segment Reporting Information [Line Items]
New vehicle retail sales									4,989,290	4,669,512	4,220,913
Used vehicle retail sales									2,204,728	1,923,740	1,728,072
Used vehicle wholesale sales									289,580	279,074	236,995
Parts and service									1,032,960	966,672	878,951
Finance and insurance									377,432	336,243	288,409
Total revenues									8,893,990	8,175,241	7,353,340
Gross profit									1,338,947	1,245,907	1,116,415
Selling, general and administrative expense									958,608	891,693	830,275
Depreciation and amortization									41,220	36,701	31,671
ASSET IMPAIRMENTS									18,983	15,570	6,542
Floorplan interest expense									(36,062)	(34,060)	(33,789)
Other interest expense, net									(52,277)	(46,516)	(37,982)
Other Expenses											0
Gains (Losses) on Extinguishment of Debt						$ 22,800	$ 23,600			(46,403)
Income before income taxes									231,797	174,964	176,156
Provision for income taxes									(89,433)	(77,715)	(70,815)
Net income									142,364	97,249	105,340
Capital expenditures									97,504	88,774	64,442
Goodwill and intangible franchise rights	1,095,434				958,144				1,095,434	958,144
Total assets	3,940,926				3,529,643				3,940,926	3,529,643
U.K. [Member]
Segment Reporting Information [Line Items]
New vehicle retail sales									641,888	519,137	441,537
Used vehicle retail sales									351,311	283,147	221,590
Used vehicle wholesale sales									100,706	82,235	66,077
Parts and service									102,183	83,747	67,557
Finance and insurance									24,117	18,986	14,028
Total revenues									1,220,205	987,252	810,789
Gross profit									137,646	115,393	93,221
Selling, general and administrative expense									108,719	90,427	74,777
Depreciation and amortization									4,307	3,403	2,573
ASSET IMPAIRMENTS									330	0	0
Floorplan interest expense									(2,276)	(1,662)	(1,589)
Other interest expense, net									(3,135)	(2,065)	(1,158)
Other Expenses											0
Gains (Losses) on Extinguishment of Debt										0
Income before income taxes									18,879	17,836	13,124
Provision for income taxes									(3,655)	(3,561)	(3,064)
Net income									15,224	14,275	10,061
Capital expenditures									9,395	3,679	1,489
Goodwill and intangible franchise rights	43,093				43,295				43,093	43,295
Total assets	358,476				327,644				358,476	327,644
Brazil [Member]
Segment Reporting Information [Line Items]
Goodwill and intangible franchise rights					132,885					132,885
Total assets					284,205					284,205
Brazil [Member]
Segment Reporting Information [Line Items]
New vehicle retail sales									370,128	552,970	562,471
Used vehicle retail sales									82,930	117,981	89,766
Used vehicle wholesale sales									6,965	17,834	29,113
Parts and service									51,050	75,275	64,177
Finance and insurance									7,237	11,336	8,925
Total revenues									518,310	775,396	754,452
Gross profit									57,379	86,638	82,910
Selling, general and administrative expense									53,506	79,844	71,804
Depreciation and amortization									1,712	2,240	1,582
ASSET IMPAIRMENTS									68,249	25,950	0
Floorplan interest expense									(926)	(5,892)	(6,289)
Other interest expense, net									(1,491)	(1,112)	169
Other Expenses											(789)
Gains (Losses) on Extinguishment of Debt										0
Income before income taxes									(68,505)	(28,400)	2,615
Provision for income taxes									4,916	9,880	(4,024)
Net income									(63,589)	(18,520)	(1,409)
Capital expenditures									333	5,256	3,285
Goodwill and intangible franchise rights	23,976								23,976
Total assets	115,527								115,527
Consolidated Entities [Member]
Segment Reporting Information [Line Items]
Goodwill and intangible franchise rights	1,162,503				1,134,324				1,162,503	1,134,324
Total assets	$ 4,414,929				$ 4,141,492				4,414,929	$ 4,141,492
Net of taxes [Member] | U.S. [Member]
Segment Reporting Information [Line Items]
ASSET IMPAIRMENTS									12,000		$ 4,000
Net of taxes [Member] | Brazil [Member]
Segment Reporting Information [Line Items]
ASSET IMPAIRMENTS									$ 62,400