Restatement of Consolidated Financial Statements, Consolidated Statement of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016
Consolidated Statements of Operations [Abstract]
Gross revenue	$ 90,684	$ 96,083	$ 98,248
Cost of professional services and other direct operating expenses	33,855	36,179	36,436
Subcontract costs		15,975	17,106
Selling, general and administrative expenses	39,257	38,139	40,970
Depreciation and amortization	1,083	994	1,042
(Loss) income from operations	(702)	4,796	2,694
Income from equity method investment	595	368	363
Interest income (expense)	114	29	(55)
Gain on insurance settlement	0	0	358
Net foreign exchange (loss) gain	(11)	(86)	44
Proxy contest costs, net	0	(375)	0
Other income (expense)	158	(54)	(104)
Income before income tax provision	154	4,678	3,300
Income tax provision	258	2,167	3,146
Net (loss) income	(104)	2,511	154
Net loss attributable to noncontrolling interests	(204)	312	587
Net (loss) income attributable to Ecology and Environment Inc.	$ (308)	$ 2,823	$ 741
Net income per common share: basic and diluted (in dollars per share)	$ (0.07)	$ 0.66	$ 0.17
Weighted average common shares outstanding: basic and diluted (in shares)	4,304,574	4,294,501	4,289,993
As Previously Reported [Member]
Consolidated Statements of Operations [Abstract]
Gross revenue		$ 104,502	$ 105,817
Cost of professional services and other direct operating expenses		38,334	38,912
Subcontract costs		18,379	18,550
Selling, general and administrative expenses		40,821	43,070
Depreciation and amortization		1,040	1,143
(Loss) income from operations		5,928	4,142
Income from equity method investment		0	0
Interest income (expense)		17	(73)
Gain on insurance settlement			358
Net foreign exchange (loss) gain		(91)	44
Proxy contest costs, net		(375)
Other income (expense)		(54)	(104)
Income before income tax provision		5,425	4,367
Income tax provision		2,472	3,759
Net (loss) income		2,953	608
Net loss attributable to noncontrolling interests		62	278
Net (loss) income attributable to Ecology and Environment Inc.		$ 3,015	$ 886
Net income per common share: basic and diluted (in dollars per share)		$ 0.70	$ 0.21
Weighted average common shares outstanding: basic and diluted (in shares)		4,294,501	4,289,993
GAC Deconsolidation Adjustments [Member]
Consolidated Statements of Operations [Abstract]
Gross revenue		$ (7,629)	$ (7,530)
Cost of professional services and other direct operating expenses		(2,837)	(3,339)
Subcontract costs		(1,687)	(1,293)
Selling, general and administrative expenses		(2,601)	(1,647)
Depreciation and amortization		(46)	(31)
(Loss) income from operations		(458)	(1,220)
Income from equity method investment		368	363
Interest income (expense)		12	18
Gain on insurance settlement			0
Net foreign exchange (loss) gain		5	0
Proxy contest costs, net		0
Other income (expense)		0	0
Income before income tax provision		(73)	(839)
Income tax provision		117	(587)
Net (loss) income		(190)	(252)
Net loss attributable to noncontrolling interests		250	276
Net (loss) income attributable to Ecology and Environment Inc.		60	24
Out of Period Adjustments [Member]
Consolidated Statements of Operations [Abstract]
Gross revenue		(790)	(39)
Cost of professional services and other direct operating expenses		682	863
Subcontract costs		(717)	(151)
Selling, general and administrative expenses		(81)	(453)
Depreciation and amortization		0	(70)
(Loss) income from operations		(674)	(228)
Income from equity method investment		0	0
Interest income (expense)		0	0
Gain on insurance settlement			0
Net foreign exchange (loss) gain		0	0
Proxy contest costs, net		0
Other income (expense)		0	0
Income before income tax provision		(674)	(228)
Income tax provision		(422)	(26)
Net (loss) income		(252)	(202)
Net loss attributable to noncontrolling interests		0	33
Net (loss) income attributable to Ecology and Environment Inc.		$ (252)	$ (169)