Condensed Consolidated Balance Sheet Parenthetical - USD ($) $ in Thousands	Apr. 30, 2019	Jul. 31, 2018
Current Assets
Allowance for doubtful accounts	$ 676	$ 817
Other Assets
Accumulated amortization of trademarks and patents	291	267
Accumulated amortization of customer lists	6,107	5,540
Noncurrent Liabilities
Net unamortized debt issuance costs	$ 39	$ 60
Common Stock
Stockholder's Equity
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares issued	8,276,949	8,086,849
Treasury stock, common shares	2,926,374	2,914,092
Common Class B
Stockholder's Equity
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares issued	2,576,479	2,468,979
Treasury stock, common shares	324,741	324,741