Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Oct. 31, 2021	Jul. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Oct. 31, 2021	Oct. 31, 2020
Computation of basic and diluted earnings per share of common stock
Net income	$ 74,361	$ 61,202	$ 28,469	$ 27,219	$ 135,563	$ 55,688
Basic earnings per common share:
Basic weighted average common shares outstanding (in shares)	43,135,000		42,723,000		43,112,000	42,674,000
Basic earnings per common share (in dollars per share)	$ 1.72		$ 0.67		$ 3.14	$ 1.30
Diluted earnings per common share:
Basic weighted average common shares outstanding (in shares)	43,135,000		42,723,000		43,112,000	42,674,000
Add: Common Stock Equivalents (in shares)	759,000		451,000		821,000	422,000
Diluted weighted average common shares outstanding (in shares)	43,894,000		43,174,000		43,933,000	43,096,000
Diluted earnings per common share (in dollars per share)	$ 1.69		$ 0.66		$ 3.09	$ 1.29
Shares were not included in the calculation of Diluted loss per common share
Anti-dilutive shares (in shares)	0		500,000		0	400,000