Income Taxes (Details 1) - USD ($) $ in Thousands	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Deferred income tax assets:
Bad debt reserve	$ 535	$ 575
Accrued expenses	7,888	5,327
Stock options and restricted stock	1,608	1,802
Charitable contributions	1,768	1,527
Impairment	27,944	25,746
Depreciation	4,438	6,785
Unrealized gain	317	193
Net operating loss	122,260	122,849
Credits	2,899	3,192
Total deferred income tax assets	169,657	167,996
Valuation allowance	(157,816)	(158,442)	$ (155,393)
Deferred tax assets, net of valuation allowance	11,841	9,554
Deferred income tax liabilities:
Unrealized loss		42
NET DEFERRED INCOME TAX ASSETS	$ 11,841	$ 9,512