Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
REVENUES	$ 2,943,462	$ 2,672,195	$ 5,803,488	$ 5,191,024
U.S.
Disaggregation of Revenue [Line Items]
REVENUES	2,168,001	2,123,690	4,256,487	4,091,409
U.K.
Disaggregation of Revenue [Line Items]
REVENUES	666,883	437,103	1,327,425	887,430
Brazil
Disaggregation of Revenue [Line Items]
REVENUES	108,578	111,402	219,576	212,185
Total new and used vehicle sales
Disaggregation of Revenue [Line Items]
REVENUES	2,470,277	2,234,094	4,868,466	4,336,391
Total new and used vehicle sales | U.S.
Disaggregation of Revenue [Line Items]
REVENUES	1,781,670	1,746,440	3,489,455	3,357,181
Total new and used vehicle sales | U.K.
Disaggregation of Revenue [Line Items]
REVENUES	593,270	390,269	1,186,408	794,787
Total new and used vehicle sales | Brazil
Disaggregation of Revenue [Line Items]
REVENUES	95,337	97,385	192,603	184,423
New vehicle retail sales
Disaggregation of Revenue [Line Items]
REVENUES	1,555,570	1,448,768	3,069,160	2,785,981
New vehicle retail sales | U.S.
Disaggregation of Revenue [Line Items]
REVENUES	1,146,882	1,143,771	2,236,835	2,162,020
New vehicle retail sales | U.K.
Disaggregation of Revenue [Line Items]
REVENUES	338,635	231,415	693,039	490,055
New vehicle retail sales | Brazil
Disaggregation of Revenue [Line Items]
REVENUES	70,053	73,582	139,286	133,906
Used vehicle retail sales
Disaggregation of Revenue [Line Items]
REVENUES	821,853	685,949	1,602,423	1,346,876
Used vehicle retail sales | U.S.
Disaggregation of Revenue [Line Items]
REVENUES	592,007	536,193	1,155,837	1,058,140
Used vehicle retail sales | U.K.
Disaggregation of Revenue [Line Items]
REVENUES	208,108	128,406	400,657	243,775
Used vehicle retail sales | Brazil
Disaggregation of Revenue [Line Items]
REVENUES	21,738	21,350	45,929	44,961
Used vehicle wholesale sales
Disaggregation of Revenue [Line Items]
REVENUES	92,854	99,377	196,883	203,534
Used vehicle wholesale sales | U.S.
Disaggregation of Revenue [Line Items]
REVENUES	42,781	66,476	96,783	137,021
Used vehicle wholesale sales | U.K.
Disaggregation of Revenue [Line Items]
REVENUES	46,527	30,448	92,712	60,957
Used vehicle wholesale sales | Brazil
Disaggregation of Revenue [Line Items]
REVENUES	3,546	2,453	7,388	5,556
Parts and service sales
Disaggregation of Revenue [Line Items]
REVENUES	358,129	331,631	707,644	651,329
Parts and service sales | U.S.
Disaggregation of Revenue [Line Items]
REVENUES	288,889	282,698	573,403	553,857
Parts and service sales | U.K.
Disaggregation of Revenue [Line Items]
REVENUES	57,996	37,050	111,137	73,831
Parts and service sales | Brazil
Disaggregation of Revenue [Line Items]
REVENUES	11,244	11,883	23,104	23,641
Vehicle parts sales
Disaggregation of Revenue [Line Items]
REVENUES	85,356	78,430	170,552	153,095
Vehicle parts sales | U.S.
Disaggregation of Revenue [Line Items]
REVENUES	73,673	70,853	148,028	137,608
Vehicle parts sales | U.K.
Disaggregation of Revenue [Line Items]
REVENUES	10,476	6,178	19,991	12,458
Vehicle parts sales | Brazil
Disaggregation of Revenue [Line Items]
REVENUES	1,207	1,399	2,533	3,029
Maintenance and repair sales
Disaggregation of Revenue [Line Items]
REVENUES	272,773	253,201	537,092	498,234
Maintenance and repair sales | U.S.
Disaggregation of Revenue [Line Items]
REVENUES	215,216	211,845	425,375	416,249
Maintenance and repair sales | U.K.
Disaggregation of Revenue [Line Items]
REVENUES	47,520	30,872	91,146	61,373
Maintenance and repair sales | Brazil
Disaggregation of Revenue [Line Items]
REVENUES	10,037	10,484	20,571	20,612
Finance, insurance and other, net
Disaggregation of Revenue [Line Items]
REVENUES	115,056	106,470	227,378	203,304
Finance, insurance and other, net | U.S.
Disaggregation of Revenue [Line Items]
REVENUES	97,442	94,552	193,629	180,371
Finance, insurance and other, net | U.K.
Disaggregation of Revenue [Line Items]
REVENUES	15,617	9,784	29,880	18,812
Finance, insurance and other, net | Brazil
Disaggregation of Revenue [Line Items]
REVENUES	$ 1,997	$ 2,134	$ 3,869	$ 4,121