Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Apr. 30, 2018	Apr. 30, 2017
Allowance for doubtful accounts receivable	$ 159	$ 171
Class A Common Shares
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	33,141,764	31,821,508
Common stock, shares Outstanding	28,553,132	27,232,876
Class A treasury stock, shares	4,588,632	4,588,632
Class B Common Shares
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	10,000,000	10,000,000
Common stock, shares issued	2,057,390	2,393,336
Common stock, shares Outstanding	2,057,390	2,393,336