Variable Interest Entities and Equity Method Investment, Equity Method Investment (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 27, 2019 USD ($)	Apr. 28, 2018 USD ($)	Apr. 27, 2019 USD ($) Employee	Apr. 28, 2018 USD ($)	Jul. 31, 2018 USD ($)
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Equity investment carrying value at beginning of period			$ 2,058
GAC net income attributable to EEI	$ 64	$ 137	295	$ 376
Equity investment carrying value at end of period	$ 2,005		$ 2,005
GAC [Member]
Equity Method Investment [Abstract]
Number of senior employees in which additional shares have been issued to | Employee			2
Ownership percentage	52.48%		52.48%		55.10%
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Equity investment carrying value at beginning of period			$ 2,058	1,464
GAC net income attributable to EEI			295	376
Dividends declared and paid during the period			(348)	0
Equity investment carrying value at end of period	$ 2,005	$ 1,840	2,005	1,840
Equity Method Investment, Summarized Financial Information [Abstract]
Current assets	5,495		5,495		$ 5,713
Noncurrent assets	1,032		1,032		501
Total assets	6,527		6,527		6,214
Current liabilities	2,832		2,832		2,620
Noncurrent liabilities	900		900		593
Total liabilities	3,732		3,732		3,213
Total Ecology and Environment Inc. shareholder's equity	1,487		1,487		1,678
Minority interests shareholders' equity	1,308		1,308		1,323
Total shareholders' equity	2,795		2,795		3,001
Total liabilities and shareholders' equity	$ 6,527		6,527		$ 6,214
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Gross revenue			9,456	8,095
Direct cost of services and subcontract costs			6,053	4,781
Income from operations			775	951
Net income			538	681
Net income attributable to EEI			$ 295	$ 376