Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Oct. 29, 2016	Oct. 31, 2015
Earnings Per Share [Abstract]
Minimum percentage right of Class B common stock holders to elect Board of Directors	75.00%
Net income attributable to Ecology and Environment, Inc.	$ 888	$ 664
Dividends declared	0	0
Balance at end of period	$ 888	$ 664
Weighted-average common shares outstanding (basic and diluted) (in shares)	4,292,733	4,288,404
Distributed earnings per share (in dollars per share)	$ 0	$ 0
Undistributed earnings per share (in dollars per share)	0.21	0.15
Total earnings per share (in dollars per share)	$ 0.21	$ 0.15