Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Computation of basic and diluted earnings per share of common stock
Net income	$ 8,650	$ 15,343
Less: Net income allocated to participating securities	156
Net income attributable to common stockholders	$ 8,494	$ 15,343
Basic earnings per common share:
Basic weighted average common shares outstanding (in shares)	41,094	40,971
Basic earnings per common share (in dollars per share)	$ 0.21	$ 0.37
Diluted earnings per common share:
Basic weighted average common shares outstanding (in shares)	41,094	40,971
Add: Common Stock Equivalents	980	1,157
Diluted weighted average common shares outstanding (in shares)	42,074	42,128
Diluted earnings per common share (in dollars per share)	$ 0.20	$ 0.36