Variable Interest Entities and Equity Method Investment, Equity Method Investment (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 27, 2018	Oct. 28, 2017	Jul. 31, 2018
Equity Method Investment, Financial Statement, Reported Amounts [Abstract]
Equity investment carrying value at beginning of period	$ 2,058
GAC net income attributable to EEI	60	$ 18
Equity investment carrying value at end of period	$ 2,118
GAC [Member]
Equity Method Investment [Abstract]
Ownership percentage	55.10%		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	60	18
Equity investment carrying value at end of period	2,118	1,482
Equity Method Investment, Summarized Financial Information [Abstract]
Current assets	5,469		$ 5,713
Noncurrent assets	348		501
Total assets	5,817		6,214
Current liabilities	2,113		2,620
Noncurrent liabilities	928		593
Total liabilities	3,041		3,213
Total Ecology and Environment Inc. shareholder's equity	1,658		1,678
Noncontrolling interests shareholders' equity	1,118		1,323
Total shareholders' equity	2,776		3,001
Total liabilities and shareholders' equity	5,817		$ 6,214
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Gross revenue	2,852	2,113
Direct cost of services and subcontract costs	1,974	1,321
Income from operations	157	54
Net income	109	33
Net income attributable to EEI	$ 60	$ 18