Segments and Other Geographic Information (Details 1) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Jul. 31, 2018		Apr. 30, 2018	[1]	Jan. 31, 2018	[1]	Oct. 31, 2017	[1]	Jul. 31, 2017		Apr. 30, 2017	[1]	Jan. 31, 2017	[1]	Oct. 31, 2016	[1]	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total service revenues and vehicle sales	$ 449,223	[1]	$ 478,198		$ 459,106		$ 419,168		$ 378,596	[1]	$ 373,862		$ 349,532		$ 345,991		$ 1,805,695	$ 1,447,981	$ 1,268,449
Yard operations																	846,868	678,401	582,904
Cost of vehicle sales																	196,461	137,552	140,959
General and administrative																	176,890	151,364	138,116
Impairment of long-lived assets																	1,131	19,365	0
Operating income	134,837	[1]	174,619		150,947		123,942		110,807	[1]	136,788		108,880		104,824		584,345	461,299	406,470
Interest (expense) income, net																	(19,075)	(22,373)	(22,157)
Other income, net																	(2,759)	1,174	11,552
Intercompany income (expense)																	0	0	0
Income before income tax expense	132,729	[1]	171,216		144,438		114,128		106,379	[1]	131,088		100,099		102,534		562,511	440,100	395,865
Income tax expense																	144,504	45,839	125,505
Net income	109,748	[1]	$ 127,348		$ 103,256		$ 77,515		70,335	[1]	$ 90,546		$ 66,066		$ 167,280		417,867	394,227	270,360
Net Income																	418,007	394,261	270,360
Depreciation and amortization																	78,598	57,000	48,575
Capital expenditures, including acquisitions																	296,697	332,990	173,917
Total assets	2,307,698								1,982,501								2,307,698	1,982,501	1,649,820
Goodwill	337,235								340,243								337,235	340,243	260,198
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Impairment of long-lived assets																	1,157
Operating segments | United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total service revenues and vehicle sales																	1,491,022	1,193,188	1,016,036
Yard operations																	730,865	585,587	494,146
Cost of vehicle sales																	101,130	61,484	55,866
General and administrative																	144,140	130,392	118,315
Impairment of long-lived assets																	0	19,365
Operating income																	514,887	396,360	347,709
Interest (expense) income, net																	(19,996)	(23,373)	(23,178)
Other income, net																	(3,285)	(10)	1,216
Intercompany income (expense)																	10,355	12,549	13,266
Income before income tax expense																	501,961	385,526	339,013
Income tax expense																	136,136	34,985	115,667
Net income																	365,825	350,541	223,346
Depreciation and amortization																	67,779	47,507	39,083
Capital expenditures, including acquisitions																	255,868	317,646	153,451
Total assets	1,856,058								1,514,018								1,856,058	1,514,018	1,249,755
Goodwill	256,434								259,162								256,434	259,162	179,906
Operating segments | International
Revenues from External Customers and Long-Lived Assets [Line Items]
Total service revenues and vehicle sales																	314,673	254,793	252,413
Yard operations																	116,003	92,814	88,758
Cost of vehicle sales																	95,331	76,068	85,093
General and administrative																	32,750	20,972	19,801
Impairment of long-lived assets																	1,131	0
Operating income																	69,458	64,939	58,761
Interest (expense) income, net																	921	1,000	1,021
Other income, net																	526	1,184	10,336
Intercompany income (expense)																	(10,355)	(12,549)	(13,266)
Income before income tax expense																	60,550	54,574	56,852
Income tax expense																	8,368	10,854	9,838
Net income																	52,182	43,720	47,014
Depreciation and amortization																	10,819	9,493	9,492
Capital expenditures, including acquisitions																	40,829	15,344	20,466
Total assets	451,640								468,483								451,640	468,483	400,065
Goodwill	$ 80,801								$ 81,081								$ 80,801	$ 81,081	$ 80,292

[1] Earnings per share were computed independently for each of the periods presented; therefore, the sum of the earnings per share amounts for the quarters may not equal the total for the year.