Investments (Details Narrative) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2022	Jan. 31, 2021	Jan. 31, 2022	Jan. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Available-for-sale debt securities maturity year description			The investments in debt securities, which include municipal bonds and bond funds, mature between June 2022 and September 2042.
Impairment loss				$ 79,000
[custom:EquitySecuritiesOfGrossRealizedGain]	$ 121,000	$ 288,000	465,000	575,000
[custom:EquitySecuritiesOfGrossRealizedLosses]	27,000	35,000	61,000	272,000
[custom:DebtSecuritiesOfGrossRealizedGains]	0		0	0
[custom:DebtSecuritiesOfGrossRealizedLoss]	$ 3,000	$ 3,000	$ 13,000	$ 9,000