Restatement of Unaudited Condensed Consolidated Financial Statements, Condensed Consolidated Statement of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Oct. 27, 2018	Oct. 28, 2017
Consolidated Statements of Operations [Abstract]
Gross revenue	$ 21,752	$ 26,105
Direct cost of services	8,134	8,618
Subcontract costs	4,574	6,349
Selling, general and administrative expenses	9,200	9,782
Depreciation and amortization	277	260
(Loss) income from operations	(433)	1,096
Income from equity method investment	60	18
Net interest income (expense)	54	2
Net foreign exchange (loss) gain	23	5
(Loss) income before income tax provision	(270)	1,121
Income tax provision	(155)	433
Net (loss) income	(115)	688
(Income) loss attributable to noncontrolling interests	(5)	(100)
Net (loss) income attributable to Ecology and Environment Inc.	$ (120)	$ 588
Net income per common share: basic and diluted (in dollars per share)	$ (0.03)	$ 0.14
Weighted average common shares outstanding: basic and diluted (in shares)	4,313,930	4,301,604
As Previously Reported [Member]
Consolidated Statements of Operations [Abstract]
Gross revenue		$ 27,082
Direct cost of services		9,480
Subcontract costs		5,729
Selling, general and administrative expenses		10,509
Depreciation and amortization		270
(Loss) income from operations		1,094
Income from equity method investment		0
Net interest income (expense)		(5)
Net foreign exchange (loss) gain		3
(Loss) income before income tax provision		1,092
Income tax provision		444
Net (loss) income		648
(Income) loss attributable to noncontrolling interests		(115)
Net (loss) income attributable to Ecology and Environment Inc.		$ 533
Net income per common share: basic and diluted (in dollars per share)		$ 0.12
Weighted average common shares outstanding: basic and diluted (in shares)		4,301,604
GAC Deconsolidation Adjustments [Member]
Consolidated Statements of Operations [Abstract]
Gross revenue		$ (2,112)
Direct cost of services		(862)
Subcontract costs		(459)
Selling, general and administrative expenses		(727)
Depreciation and amortization		(10)
(Loss) income from operations		(54)
Income from equity method investment		18
Net interest income (expense)		7
Net foreign exchange (loss) gain		2
(Loss) income before income tax provision		(27)
Income tax provision		(12)
Net (loss) income		(15)
(Income) loss attributable to noncontrolling interests		15
Net (loss) income attributable to Ecology and Environment Inc.		0
Out of Period Adjustments [Member]
Consolidated Statements of Operations [Abstract]
Gross revenue		1,135
Direct cost of services		0
Subcontract costs		1,079
Selling, general and administrative expenses		0
Depreciation and amortization		0
(Loss) income from operations		56
Income from equity method investment		0
Net interest income (expense)		0
Net foreign exchange (loss) gain		0
(Loss) income before income tax provision		56
Income tax provision		1
Net (loss) income		55
(Income) loss attributable to noncontrolling interests		0
Net (loss) income attributable to Ecology and Environment Inc.		$ 55