Condensed Consolidated Statements of Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Retained Earnings
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 (net of tax withholding on employee share-based awards)	(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
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	232,575
Ending Balance (shares) at Oct. 31, 2020		36,935,747,000
Ending Balance at Oct. 31, 2020	1,859,851	$ 41,114	1,818,737
Beginning Balance (shares) at Jul. 31, 2020		36,906,773,000
Beginning Balance at Jul. 31, 2020	1,751,238	$ 32,601	1,718,637
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	111,983		111,983
Dividends declared	(11,883)		(11,883)
Exercise of stock options (in shares)		23,470,000
Exercise of stock options	1,042	$ 1,042
Share-based compensation (shares)		5,504,000
Share-based compensation (net of tax withholding on employee share-based awards)	7,471	$ 7,471
Ending Balance (shares) at Oct. 31, 2020		36,935,747,000
Ending Balance at Oct. 31, 2020	1,859,851	$ 41,114	1,818,737
Beginning Balance (shares) at Apr. 30, 2021		36,949,878,000
Beginning Balance at Apr. 30, 2021	1,932,679	$ 58,951	1,873,728
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	119,159		119,159
Dividends declared	(12,680)		(12,680)
Exercise of stock options (in shares)		3,000,000
Exercise of stock options	133	$ 133
Share-based compensation (shares)		149,368,000
Share-based compensation (net of tax withholding on employee share-based awards)	(8,626)	$ (8,626)
Ending Balance (shares) at Jul. 31, 2021		37,102,246,000
Ending Balance at Jul. 31, 2021	2,030,665	$ 50,458	1,980,207
Beginning Balance (shares) at Apr. 30, 2021		36,949,878,000
Beginning Balance at Apr. 30, 2021	1,932,679	$ 58,951	1,873,728
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	215,990
Ending Balance (shares) at Oct. 31, 2021		37,108,803,000
Ending Balance at Oct. 31, 2021	2,123,134	$ 59,214	2,063,920
Beginning Balance (shares) at Jul. 31, 2021		37,102,246,000
Beginning Balance at Jul. 31, 2021	2,030,665	$ 50,458	1,980,207
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	96,831		96,831
Dividends declared	(13,118)		(13,118)
Share-based compensation (shares)		6,557,000
Share-based compensation (net of tax withholding on employee share-based awards)	8,756	$ 8,756
Ending Balance (shares) at Oct. 31, 2021		37,108,803,000
Ending Balance at Oct. 31, 2021	$ 2,123,134	$ 59,214	$ 2,063,920