Investments - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Net Investment Income [Line Items]
Carrying value of investment	$ 16,800	$ 16,000
Marketable equity securities
Net Investment Income [Line Items]
Net unrealized holding gains (losses)	600	3,500	$ 700
Net realized holding gains (losses)	(200)	100	(200)
Portfolio debt securities
Net Investment Income [Line Items]
Net unrealized holding gains (losses)	24	74	(600)
Net realized holding gains (losses)	$ (38)	$ (100)	$ 700

Sum of the carrying amounts as of the balance sheet date of all investments.

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