Restatement of Unaudited Condensed Consolidated Financial Statements, Condensed Consolidated Statement of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 26, 2019	Jan. 27, 2018	Jan. 26, 2019	Jan. 27, 2018
Consolidated Statements of Operations [Abstract]
Gross revenue	$ 20,252	$ 21,289	$ 42,004	$ 47,394
Direct cost of professional services and other direct operating expenses	7,774	7,966	15,908	16,584
Subcontract costs	3,619	4,429	8,193	10,778
Selling, general and administrative expenses	9,452	9,483	18,652	19,265
Depreciation and amortization	264	259	541	519
(Loss) income from operations	(857)	(848)	(1,290)	248
Income from equity method investment	171	221	231	239
Net interest income (expense)	45	(4)	98	(2)
Net foreign exchange (loss) gain	(15)	(25)	8	(20)
Other income (expense)	(19)	12	9	12
(Loss) income before income tax provision	(675)	(644)	(944)	477
Income tax provision	(365)	(116)	(519)	317
Net (loss) income	(310)	(528)	(425)	160
(Income) loss attributable to noncontrolling interests	1	9	(4)	(91)
Net (loss) income attributable to Ecology and Environment Inc.	$ (309)	$ (519)	$ (429)	$ 69
Net (loss) income per common share: basic and diluted (in dollars per share)	$ (0.07)	$ (0.12)	$ (0.10)	$ 0.02
Weighted average common shares outstanding: basic and diluted (in shares)	4,315,135	4,301,604	4,314,543	4,301,604
As Previously Reported [Member]
Consolidated Statements of Operations [Abstract]
Gross revenue		$ 25,083		$ 52,165
Direct cost of professional services and other direct operating expenses		9,078		18,559
Subcontract costs		5,769		11,498
Selling, general and administrative expenses		10,228		20,737
Depreciation and amortization		268		537
(Loss) income from operations		(260)		834
Income from equity method investment		0		0
Net interest income (expense)		(9)		(14)
Net foreign exchange (loss) gain		(29)		(26)
Other income (expense)		12		12
(Loss) income before income tax provision		(286)		806
Income tax provision		311		755
Net (loss) income		(597)		51
(Income) loss attributable to noncontrolling interests		(171)		(286)
Net (loss) income attributable to Ecology and Environment Inc.		$ (768)		$ (235)
Net (loss) income per common share: basic and diluted (in dollars per share)		$ (0.18)		$ (0.05)
Weighted average common shares outstanding: basic and diluted (in shares)		4,301,604		4,301,604
GAC Deconsolidation Adjustments [Member]
Consolidated Statements of Operations [Abstract]
Gross revenue		$ (3,154)		$ (5,266)
Direct cost of professional services and other direct operating expenses		(1,112)		(1,975)
Subcontract costs		(731)		(1,190)
Selling, general and administrative expenses		(745)		(1,472)
Depreciation and amortization		(9)		(18)
(Loss) income from operations		(557)		(611)
Income from equity method investment		221		239
Net interest income (expense)		5		12
Net foreign exchange (loss) gain		4		6
Other income (expense)		0		0
(Loss) income before income tax provision		(327)		(354)
Income tax provision		(148)		(160)
Net (loss) income		(179)		(194)
(Income) loss attributable to noncontrolling interests		179		194
Net (loss) income attributable to Ecology and Environment Inc.		0		0
Out of Period Adjustments [Member]
Consolidated Statements of Operations [Abstract]
Gross revenue		(640)		495
Direct cost of professional services and other direct operating expenses		0		0
Subcontract costs		(609)		470
Selling, general and administrative expenses		0		0
Depreciation and amortization		0		0
(Loss) income from operations		(31)		25
Income from equity method investment		0		0
Net interest income (expense)		0		0
Net foreign exchange (loss) gain		0		0
Other income (expense)		0		0
(Loss) income before income tax provision		(31)		25
Income tax provision		(279)		(278)
Net (loss) income		248		303
(Income) loss attributable to noncontrolling interests		1		1
Net (loss) income attributable to Ecology and Environment Inc.		$ 249		$ 304