Stock-Based Compensation Stock Option Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Shares
Options granted (in shares)	0	0	0
Stock options
Intrinsic value of options
Intrinsic value of options exercised	$ 4,785	$ 4,828	$ 833
Intrinsic value of options outstanding	9,229	24,068
Intrinsic value of exercisable options	$ 9,229	$ 24,068
Restated 2006 Plan | Stock options
Shares
Outstanding at the beginning of the year (in shares)	280,526	334,026	337,026
Options exercised (in shares)	(114,362)	(53,500)	(3,000)
Outstanding at the end of the year (in shares)	166,164	280,526	334,026
Options exercisable (in shares)	166,164
Weighted Average Exercise Price
Outstanding at the beginning of the year (in dollars per share)	$ 24.57	$ 25.19	$ 25.25
Options exercised (in dollars per share)	24.28	28.45	31.15
Outstanding at the end of the year (in dollars per share)	24.78	$ 24.57	$ 25.19
Options exercisable (in dollars per share)	$ 24.78
1992 Plan | Stock options
Shares
Outstanding at the beginning of the year (in shares)		1,113	14,302
Options exercised (in shares)		(1,113)	(13,189)
Outstanding at the end of the year (in shares)			1,113
Weighted Average Exercise Price
Outstanding at the beginning of the year (in dollars per share)		$ 0.59	$ 0.59
Options exercised (in dollars per share)		$ 0.59	0.59
Outstanding at the end of the year (in dollars per share)			$ 0.59