Quarterly Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended																12 Months Ended
		Jul. 31, 2020		Apr. 30, 2020		Jan. 31, 2020		Oct. 31, 2019		Jul. 31, 2019		Apr. 30, 2019		Jan. 31, 2019		Oct. 31, 2018		Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenues	[1]	$ 525,659		$ 550,360		$ 575,140		$ 554,424		$ 542,575		$ 553,116		$ 484,898		$ 461,368
Gross profit	[1]	250,431		242,613		259,889		254,869		242,619		251,579		208,226		195,918
Operating income		205,715	[1]	195,101	[1]	209,892	[1]	205,391	[1]	192,802	[1]	207,494	[1]	164,739	[1]	151,440	[1]	$ 816,099	$ 716,475	$ 584,345
Income before income taxes		201,883	[1]	191,800	[1]	205,074	[1]	202,082	[1]	187,070	[1]	204,129	[1]	164,966	[1]	148,786	[1]	800,839	704,951	562,511
Net income attributable to Copart, Inc.		$ 165,533	[1]	$ 147,487	[1]	$ 168,707	[1]	$ 218,180	[1]	$ 153,496	[1]	$ 192,741	[1]	$ 131,373	[1]	$ 114,083	[1]	$ 699,907	$ 591,693	$ 417,867
Basic net income per common share		$ 0.70	[1]	$ 0.63	[1]	$ 0.73	[1]	$ 0.94	[1]	$ 0.67	[1]	$ 0.85	[1]	$ 0.57	[1]	$ 0.49	[1]	$ 3.00	$ 2.57	$ 1.80
Diluted net income per common share		$ 0.69	[1]	$ 0.62	[1]	$ 0.71	[1]	$ 0.91	[1]	$ 0.64	[1]	$ 0.81	[1]	$ 0.55	[1]	$ 0.47	[1]	$ 2.93	$ 2.46	$ 1.73

[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.