Variable Interest Entities and Equity Method Investment, Variable Interest Entities (Details) - USD ($) $ in Thousands	12 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Current assets	$ 42,998	$ 43,590
Total assets	51,810	52,829
Current liabilities	18,022	16,328
Total Ecology and Environment Inc. shareholder's equity	32,868	35,783
Noncontrolling interests shareholders' equity	907	664
Total shareholders' equity	33,775	36,447
Total liabilities and shareholders' equity	51,810	52,829
Gross revenue	88,510	90,684	$ 96,083
Variable Interest Entity [Member]
Variable Interest Entity, Consolidated, Carrying Amount, Assets and Liabilities, Net [Abstract]
Current assets	3,549	2,359
Noncurrent assets	781	878
Total assets	4,330	3,237
Current liabilities	5,728	5,408
Noncurrent liabilities	12	32
Total liabilities	5,740	5,440
Total Ecology and Environment Inc. shareholder's equity	(708)	(1,051)
Noncontrolling interests shareholders' equity	(702)	(1,152)
Total shareholders' equity	(1,410)	(2,203)
Total liabilities and shareholders' equity	4,330	3,237
Gross revenue	12,100	10,000	$ 8,900
Restricted cash	$ 300	$ 300