Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Apr. 30, 2019	Apr. 30, 2018
Trade accounts receivable, allowance for doubtful accounts	$ 153	$ 159
Class A Common Shares
Common stock, par value (in usd per share)	$ 0.10	$ 0.10
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	33,979,739	33,141,764
Common stock, shares issued, net	29,391,107	28,553,132
Common stock, shares Outstanding	33,979,739	33,141,764
Common stock, shares Outstanding, net	29,391,107	28,553,132
Class A treasury stock shares	4,588,632	4,588,632
Class B Common Shares
Common stock, par value (in usd per share)	$ 0.10	$ 0.10
Common stock, shares authorized	10,000,000	10,000,000
Common stock, shares issued	1,821,591	2,057,390
Common stock, shares Outstanding	1,821,591	2,057,390