Condensed Consolidated Statements Of Changes In Stockholders' Equity - USD ($)	Preferred Stock [Member]	Common Stock [Member]	Capital In Excess Of Par Value [Member]	Retained Earnings [Member]	Total
Balance at Apr. 30, 2019		$ 42,146	$ 23,474,379	$ 34,770,924	$ 58,287,449
Net (loss) income				361,025	361,025
Balance at Jul. 31, 2019		42,146	23,474,379	35,131,944	58,648,469
Balance at Apr. 30, 2019		42,146	23,474,379	34,770,924	58,287,449
Net (loss) income					1,022,208
Balance at Oct. 31, 2019		42,146	23,474,379	35,793,127	59,309,652
Cumulative-effect adjustment for the adoption of Topic 842				(5)	(5)
Balance at Jul. 31, 2019		42,146	23,474,379	35,131,944	58,648,469
Net (loss) income				661,183	661,183
Balance at Oct. 31, 2019		42,146	23,474,379	35,793,127	59,309,652
Balance at Apr. 30, 2020		42,265	23,619,513	35,214,021	58,875,799
Restricted stock awards		31	15,198		15,229
Net (loss) income				(900,666)	(900,666)
Balance at Jul. 31, 2020		42,296	23,634,711	34,313,355	57,990,362
Balance at Apr. 30, 2020		42,265	23,619,513	35,214,021	58,875,799
Net (loss) income					(273,808)
Balance at Oct. 31, 2020		42,296	23,634,711	34,940,213	58,617,220
Balance at Jul. 31, 2020		42,296	23,634,711	34,313,355	57,990,362
Net (loss) income				626,858	626,858
Balance at Oct. 31, 2020		$ 42,296	$ 23,634,711	$ 34,940,213	$ 58,617,220