Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Jul. 31, 2019	Jul. 31, 2018
Computation of basic and diluted earnings per share of common stock
Net income		$ 24,820	$ 8,650
Less: Net income allocated to participating securities		319	156
Net income attributable to common stockholders		$ 24,501	$ 8,494
Basic earnings per common share:
Basic weighted average common shares outstanding (in shares)		41,001	41,094
Basic earnings per common share (in dollars per share)	[1]	$ 0.60	$ 0.21
Diluted earnings per common share:
Basic weighted average common shares outstanding (in shares)		41,001	41,094
Add: Common Stock Equivalents		614	980
Diluted weighted average common shares outstanding (in shares)		41,615	42,074
Diluted earnings per common share (in dollars per share)	[1]	$ 0.59	$ 0.20

[1] See Note 15 for detailed calculations