Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Jan. 31, 2020	Jan. 31, 2019
Computation of basic and diluted earnings per share of common stock
Net income	$ 10,879	$ 29,138	$ 24,820	$ 5,815	$ 24,912	$ 8,650	$ 64,837	$ 39,377
Less: Net income allocated to participating securities				156			273	940
Net income attributable to common stockholders	$ 10,879			$ 5,659			$ 64,564	$ 38,437
Basic earnings per common share:
Basic weighted average common shares outstanding (in shares)	42,223			40,912			41,663	41,053
Basic earnings per common share (in dollars per share)	$ 0.26			$ 0.14			$ 1.55	$ 0.94
Diluted earnings per common share:
Basic weighted average common shares outstanding (in shares)	42,223			40,912			41,663	41,053
Add: Common Stock Equivalents	726			459			738	736
Diluted weighted average common shares outstanding (in shares)	42,949			41,371			42,401	41,789
Diluted earnings per common share (in dollars per share)	$ 0.25			$ 0.14			$ 1.52	$ 0.92