Quarterly Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended																12 Months Ended
		Jul. 31, 2018		Apr. 30, 2018		Jan. 31, 2018		Oct. 31, 2017		Jul. 31, 2017		Apr. 30, 2017		Jan. 31, 2017		Oct. 31, 2016		Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenues		$ 449,223	[1]	$ 478,198	[1]	$ 459,106	[1]	$ 419,168	[1]	$ 378,596	[1]	$ 373,862	[1]	$ 349,532	[1]	$ 345,991	[1]	$ 1,805,695	$ 1,447,981	$ 1,268,449
Gross profit	[1]	188,425		219,068		191,609		163,264		167,465		172,505		146,765		145,293
Operating income		134,837	[1]	174,619	[1]	150,947	[1]	123,942	[1]	110,807	[1]	136,788	[1]	108,880	[1]	104,824	[1]	584,345	461,299	406,470
Income before income taxes		132,729	[1]	171,216	[1]	144,438	[1]	114,128	[1]	106,379	[1]	131,088	[1]	100,099	[1]	102,534	[1]	562,511	440,100	395,865
Net income attributable to Copart, Inc.		$ 109,748	[1]	$ 127,348	[1]	$ 103,256	[1]	$ 77,515	[1]	$ 70,335	[1]	$ 90,546	[1]	$ 66,066	[1]	$ 167,280	[1]	$ 417,867	$ 394,227	$ 270,360
Basic net income per common share		$ 0.47	[1]	$ 0.55	[1]	$ 0.45	[1]	$ 0.34	[1]	$ 0.31	[1]	$ 0.39	[1]	$ 0.29	[1]	$ 0.74	[1]	$ 1.80	$ 1.72	$ 1.18
Diluted net income per common share		$ 0.45	[1]	$ 0.52	[1]	$ 0.43	[1]	$ 0.32	[1]	$ 0.30	[1]	$ 0.38	[1]	$ 0.28	[1]	$ 0.70	[1]	$ 1.73	$ 1.66	$ 1.11

[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.