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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 2,889,058	$ 3,012,292	$ 8,692,546	$ 8,203,316
Income (loss) before income taxes	44,365	47,143	165,720	160,029
Provision for income taxes	(9,587)	(17,262)	(38,666)	(57,076)
Net income	34,778	29,881	127,054	102,953
Loss for non-cash asset impairments	23,159	9,526	27,427	9,526
U.S.
Segment Reporting Information [Line Items]
Revenues	2,200,230	2,301,959	6,456,717	6,393,368
Income (loss) before income taxes	43,415	41,133	152,867	142,808
Provision for income taxes	(9,061)	(16,258)	(35,821)	(54,301)
Net income	34,354	24,875	117,046	88,507
Gain on real estate and dealership transactions	4,100		19,300
Loss for non-cash asset impairments	17,700		20,800
Gain (loss) for litigation settlements	1,100		(400)
Loss due to catastrophic events		9,000	4,400	9,400
Impact of chargeback reserves for finance and insurance revenues associated with catastrophic events		6,600		6,600
U.S. | Net of Taxes
Segment Reporting Information [Line Items]
Loss for non-cash asset impairments		5,900		5,900
U.K.
Segment Reporting Information [Line Items]
Revenues	585,936	590,726	1,913,361	1,478,156
Income (loss) before income taxes	2,663	5,435	14,416	15,745
Provision for income taxes	(366)	(1,105)	(2,131)	(2,781)
Net income	2,297	4,330	12,285	12,964
Brazil
Segment Reporting Information [Line Items]
Revenues	102,892	119,607	322,468	331,792
Income (loss) before income taxes	(1,713)	575	(1,563)	1,476
Provision for income taxes	(160)	101	(714)	6
Net income	(1,873)	$ 676	(2,277)	$ 1,482
Gain (loss) for litigation settlements	$ (2,600)		$ (3,100)