Restatement of Unaudited Condensed Consolidated Financial Statements, Condensed Consolidated Statements of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jan. 26, 2019	Jan. 27, 2018	Jan. 26, 2019	Jan. 27, 2018
Consolidated Statements of Comprehensive Income [Abstract]
Net (loss) income including noncontrolling interests	$ (310)	$ (528)	$ (425)	$ 160
Foreign currency translation adjustments	47	51	(80)	37
Unrealized investment (losses) gains, net	0	(13)	0	(16)
Comprehensive (loss) income	(263)	(490)	(505)	181
Comprehensive (income) loss attributable to noncontrolling interests	8	(29)	63	(123)
Comprehensive (loss) income attributable to Ecology and Environment, Inc.	$ (255)	(519)	$ (442)	58
As Previously Reported [Member]
Consolidated Statements of Comprehensive Income [Abstract]
Net (loss) income including noncontrolling interests		(597)		51
Foreign currency translation adjustments		166		195
Unrealized investment (losses) gains, net		(13)		(16)
Comprehensive (loss) income		(444)		230
Comprehensive (income) loss attributable to noncontrolling interests		(264)		(393)
Comprehensive (loss) income attributable to Ecology and Environment, Inc.		(708)		(163)
GAC Deconsolidation Adjustments [Member]
Consolidated Statements of Comprehensive Income [Abstract]
Net (loss) income including noncontrolling interests		(179)		(194)
Foreign currency translation adjustments		(115)		(158)
Unrealized investment (losses) gains, net		0		0
Comprehensive (loss) income		(294)		(352)
Comprehensive (income) loss attributable to noncontrolling interests		235		270
Comprehensive (loss) income attributable to Ecology and Environment, Inc.		(59)		(82)
Out of Period Adjustments [Member]
Consolidated Statements of Comprehensive Income [Abstract]
Net (loss) income including noncontrolling interests		248		303
Foreign currency translation adjustments		0		0
Unrealized investment (losses) gains, net		0		0
Comprehensive (loss) income		248		303
Comprehensive (income) loss attributable to noncontrolling interests		0		0
Comprehensive (loss) income attributable to Ecology and Environment, Inc.		$ 248		$ 303

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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