Segment Information - Reportable Segment Revenue, Income (Loss) Before Income Taxes, (Provision) Benefit for Income Taxes and Net Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
REVENUES	$ 2,943,462	$ 2,672,195	$ 5,803,488	$ 5,191,024
Income before income taxes	75,188	61,690	121,355	112,886
Provision for income taxes	(18,725)	(22,557)	(29,078)	(39,814)
Net income	56,463	39,133	92,277	73,072
Loss for non-cash asset impairments	4,268	0	4,268	0
U.S.
Segment Reporting Information [Line Items]
REVENUES	2,168,001	2,123,690	4,256,487	4,091,409
Income before income taxes	68,942	56,069	109,452	101,675
Provision for income taxes	(17,402)	(21,696)	(26,759)	(38,043)
Net income	51,540	34,373	82,693	63,632
Gain on real estate and dealership transactions	15,200		15,200
Loss due to catastrophic events	4,400		4,400
Loss for non-cash asset impairments	3,200		3,200
Loss for litigation settlements	(1,500)		(1,500)
U.S. | Net of Taxes
Segment Reporting Information [Line Items]
After-tax gain on legal settlement				1,100
U.K.
Segment Reporting Information [Line Items]
REVENUES	666,883	437,103	1,327,425	887,430
Income before income taxes	6,016	4,929	11,753	10,310
Provision for income taxes	(903)	(806)	(1,765)	(1,676)
Net income	5,113	4,123	9,988	8,634
Brazil
Segment Reporting Information [Line Items]
REVENUES	108,578	111,402	219,576	212,185
Income before income taxes	230	692	150	901
Provision for income taxes	(420)	(55)	(554)	(95)
Net income	(190)	$ 637	$ (404)	$ 806
Loss for litigation settlements	$ 500