Segments and Other Geographic Reporting Segment Reporting (Details) $ in Thousands	3 Months Ended				6 Months Ended
	Jan. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Jan. 31, 2018 USD ($)	Oct. 31, 2017 USD ($)	Jan. 31, 2019 USD ($)	Jan. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of Operating Segments					2
Number of Reportable Segments					2
Service revenues and vehicle sales:	$ 484,898		$ 459,106		$ 946,266	$ 878,274
Yard operations	215,460		217,184		423,154	434,791
Cost of vehicle sales	61,212		50,313		118,968	88,610
General and administrative	43,487		40,662		87,965	79,984
Operating income	164,739		150,947		316,179	274,889
Interest (expense) income, net	(4,555)		(5,561)		(8,246)	(10,959)
Other (expense) income, net	4,782		(948)		5,819	(5,364)
Intercompany income (expense)	0		0		0	0
Income before income taxes	164,966		144,438		313,752	258,566
Income taxes	33,593		41,137		68,296	77,705
Net income (Loss), Including Portion Attributable to Noncontrolling Interest	131,373	$ 114,083	103,301	$ 77,560	245,456	180,861
Depreciation and amortization	20,399		17,871		42,268	33,773
Capital expenditures, including acquisitions	74,391		69,421		136,727	110,782
Total assets	2,296,905				2,296,905		$ 2,307,698
Goodwill	338,045				338,045		337,235
Net Income (Loss) Attributable to Parent	131,373		103,256		245,456	180,771
Operating Segments | United States
Segment Reporting Information [Line Items]
Cost of vehicle sales	26,883		28,794		52,826	47,554
Operating Segments | International
Segment Reporting Information [Line Items]
Cost of vehicle sales	34,329		21,519		66,142	41,056
Operating Segments | United States | United States
Segment Reporting Information [Line Items]
Service revenues and vehicle sales:	390,072		385,135		761,281	736,240
Yard operations	181,335		189,378		358,977	382,211
General and administrative	36,452		33,953		73,784	67,446
Operating income	145,402		133,010		275,694	239,029
Interest (expense) income, net	(4,674)		(5,628)		(8,488)	(11,116)
Other (expense) income, net	4,674		(490)		5,299	(4,601)
Intercompany income (expense)	1,931		1,182		3,342	3,486
Income before income taxes	147,333		128,074		275,847	226,798
Income taxes	32,799		37,677		63,265	71,262
Net income (Loss), Including Portion Attributable to Noncontrolling Interest	114,534		90,397		212,582	155,536
Depreciation and amortization	17,877		14,054		37,269	27,583
Capital expenditures, including acquisitions	66,901		56,804		102,154	95,709
Total assets	1,848,216				1,848,216		1,856,058
Goodwill	256,434				256,434		256,434
Operating Segments | International | International
Segment Reporting Information [Line Items]
Service revenues and vehicle sales:	94,826		73,971		184,985	142,034
Yard operations	34,125		27,806		64,177	52,580
General and administrative	7,035		6,709		14,181	12,538
Operating income	19,337		17,937		40,485	35,860
Interest (expense) income, net	119		67		242	157
Other (expense) income, net	108		(458)		520	(763)
Intercompany income (expense)	(1,931)		(1,182)		(3,342)	(3,486)
Income before income taxes	17,633		16,364		37,905	31,768
Income taxes	794		3,460		5,031	6,443
Net income (Loss), Including Portion Attributable to Noncontrolling Interest	16,839		12,904		32,874	25,325
Depreciation and amortization	2,522		3,817		4,999	6,190
Capital expenditures, including acquisitions	7,490		12,617		34,573	15,073
Total assets	448,689				448,689		451,640
Goodwill	81,611				81,611		$ 80,801
Service revenues
Segment Reporting Information [Line Items]
Service revenues and vehicle sales:	416,807		401,954		811,613	776,079
Service revenues | Operating Segments | United States | United States
Segment Reporting Information [Line Items]
Service revenues and vehicle sales:	362,023		355,542		705,596	686,933
Service revenues | Operating Segments | International | International
Segment Reporting Information [Line Items]
Service revenues and vehicle sales:	54,784		46,412		106,017	89,146
Vehicle sales
Segment Reporting Information [Line Items]
Service revenues and vehicle sales:	68,091		57,152		134,653	102,195
Vehicle sales | Operating Segments | United States | United States
Segment Reporting Information [Line Items]
Service revenues and vehicle sales:	28,049		29,593		55,685	49,307
Vehicle sales | Operating Segments | International | International
Segment Reporting Information [Line Items]
Service revenues and vehicle sales:	$ 40,042		$ 27,559		$ 78,968	$ 52,888