Variable Interest Entities and Equity Method Investment, Equity Method Investment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 26, 2019	Jan. 27, 2018	Jan. 26, 2019	Jan. 27, 2018	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	$ 171	$ 221	231	$ 239
Equity investment carrying value at end of period	$ 2,289		$ 2,289
GAC [Member]
Equity Method Investment [Abstract]
Ownership percentage	55.10%		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			231	239
Equity investment carrying value at end of period	$ 2,289	$ 1,703	2,289	1,703
Equity Method Investment, Summarized Financial Information [Abstract]
Current assets	5,017		5,017		$ 5,713
Noncurrent assets	755		755		501
Total assets	5,772		5,772		6,214
Current liabilities	1,631		1,631		2,620
Noncurrent liabilities	939		939		593
Total liabilities	2,570		2,570		3,213
Total Ecology and Environment Inc. shareholder's equity	1,840		1,840		1,678
Noncontrolling interests shareholders' equity	1,362		1,362		1,323
Total shareholders' equity	3,202		3,202		3,001
Total liabilities and shareholders' equity	$ 5,772		5,772		$ 6,214
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]
Gross revenue			6,147	5,267
Direct cost of services and subcontract costs			3,682	3,165
Income from operations			597	611
Net income			419	434
Net income attributable to EEI			$ 231	$ 239