Investments - Narrative (Details)	1 Months Ended	12 Months Ended
	Nov. 30, 2020 USD ($)	Apr. 30, 2022 USD ($) investment	Apr. 30, 2021 USD ($) investment	Apr. 30, 2020 USD ($) investment
Investments, Debt and Equity Securities [Abstract]
Number of investment positions in unrealized loss position | investment		284	8
Number of investments, other-than-temporary impaired | investment		0	0	0
Other-than-temporary impairment loss		$ 0
Non-marketable equity securities, cost		0	$ 0	$ 700,000
Non-marketable equity securities, impairment		0	0	1,025,000
Non-marketable equity securities, proceeds from sale	$ 700,000	$ 0	$ 725,000	$ 0