Condensed Consolidated Statements of Shareholders' Equity Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Retained Earnings
Beginning Balance (shares) at Apr. 30, 2019		36,664,521,000
Beginning Balance at Apr. 30, 2019	$ 1,408,769	$ 15,600	$ 1,393,169
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	85,815		85,815
Dividends declared	(11,772)		(11,772)
Exercise of stock options (in shares)		50,931,000
Exercise of stock options	2,261	$ 2,261
Share-based compensation (shares)		67,182,000
Share-based compensation	4,141	$ 4,141
Ending Balance (shares) at Jul. 31, 2019		36,782,634,000
Ending Balance at Jul. 31, 2019	1,489,214	$ 22,002	1,467,212
Beginning Balance (shares) at Apr. 30, 2020		36,806,325,000
Beginning Balance at Apr. 30, 2020	1,643,205	$ 33,286	1,609,919
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	120,592		120,592
Dividends declared	(11,874)		(11,874)
Exercise of stock options (in shares)		4,748,000
Exercise of stock options	211	$ 211
Share-based compensation (shares)		95,700,000
Share-based compensation	(896)	$ (896)
Ending Balance (shares) at Jul. 31, 2020		36,906,773,000
Ending Balance at Jul. 31, 2020	$ 1,751,238	$ 32,601	$ 1,718,637