Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($)	Apr. 30, 2016	Jul. 31, 2015
Current assets:
Allowance for doubtful accounts and contract adjustments	$ 5,798,094	$ 5,954,261
Accumulated depreciation	$ 23,440,753	$ 23,438,269
Shareholders' equity:
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	2,000,000	2,000,000
Preferred stock, shares issued (in shares)	0	0
Class A [Member]
Shareholders' equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	6,000,000	6,000,000
Common stock, shares issued (in shares)	3,035,778	3,023,206
Treasury stock (in shares)	38,990	42,245
Class B [Member]
Shareholders' equity:
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	10,000,000	10,000,000
Common stock, shares issued (in shares)	1,357,947	1,370,519
Treasury stock (in shares)	64,801	64,801