Significant Adjustments During the Three Months Ended July 31, 2016 (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jul. 31, 2016	Jul. 31, 2016
South America [Member] | Subsidiaries [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Increase in general and administrative expense	$ 0.6
Increase in income tax provision	0.1
Increase (decrease) in net income attributable to Ecology and Environment, Inc.	0.3
U.S. and South American Operations [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Increase in income tax provision	0.4	$ 0.4
Increase (decrease) in net income attributable to Ecology and Environment, Inc.	$ (0.2)	$ (0.2)