Variable Interest Entities and Equity Method Investment, Variable Interest Entities (Details) $ in Thousands	3 Months Ended
	Oct. 27, 2018 USD ($) Subsidiary	Oct. 28, 2017 USD ($)	Jul. 31, 2018 USD ($) Subsidiary
Variable Interest Entity [Abstract]
Current assets	$ 44,581		$ 43,590
Total assets	53,411		52,829
Current liabilities	17,106		16,328
Total Ecology and Environment Inc. shareholder's equity	35,656		35,783
Noncontrolling interests shareholders' equity	605		664
Total shareholders' equity	36,261		36,447
Total liabilities and shareholders' equity	$ 53,411		$ 52,829
Number of majority owned subsidiaries | Subsidiary	1		1
Total gross revenue of consolidated variable interest entities	$ 21,752	$ 26,105
Variable Interest Entity [Member]
Variable Interest Entity [Abstract]
Current assets	2,580		$ 2,359
Noncurrent assets	682		878
Total assets	3,262		3,237
Current liabilities	5,279		5,408
Noncurrent liabilities	27		32
Total liabilities	5,306		5,440
Total Ecology and Environment Inc. shareholder's equity	(937)		(1,051)
Noncontrolling interests shareholders' equity	(1,107)		(1,152)
Total shareholders' equity	(2,044)		(2,203)
Total liabilities and shareholders' equity	3,262		3,237
Total gross revenue of consolidated variable interest entities	2,400	$ 2,400
Restricted cash	$ 200		$ 300