Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2021	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2021		Apr. 30, 2020		Apr. 30, 2019
Earnings Per Share [Abstract]
Net income	$ 33,746	$ 16,126	$ 28,469	$ 27,219	$ (41,456)	$ 10,879	$ 29,138	$ 24,820	$ 105,560		$ 23,381		$ 56,002
Less: Net income allocated to participating securities									0		74		1,382
Net income attributable to common stockholders									$ 105,560		$ 23,307		$ 54,620
Basic earnings per common share:
Basic weighted average common shares outstanding (in shares)	42,994	42,726	42,723	42,624	42,435	42,223	41,761	41,001	42,765		41,853		40,914
Basic earnings per common share (in dollars per share)	$ 0.78	$ 0.38	$ 0.67	$ 0.64	$ (0.98)	$ 0.26	$ 0.70	$ 0.60	$ 2.47	[1]	$ 0.56	[1]	$ 1.33	[1]
Diluted earnings per common share:
Basic weighted average common shares outstanding (in shares)	42,994	42,726	42,723	42,624	42,435	42,223	41,761	41,001	42,765		41,853		40,914
Add: Common Stock Equivalents									578		651		675
Diluted weighted average common shares outstanding (in shares)	43,828	43,361	43,174	43,017	42,435	42,949	42,635	41,615	43,343		42,504		41,589
Diluted earnings per common share (in dollars per share)	$ 0.77	$ 0.37	$ 0.66	$ 0.63	$ (0.98)	$ 0.25	$ 0.68	$ 0.59	$ 2.44	[1]	$ 0.55	[1]	$ 1.31	[1]
Shares were not included in the calculation of Diluted loss per common share
Anti-dilutive shares (in shares)									300		800		600

[1] See Note 18 for detailed calculations.