Statements of Stockholders' Equity - USD ($)	Preferred Stock [Member]	Common Stock Class A [Member]	Paid-In Capital [Member]	Treasury Stock (Common Class A) [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings [Member]	Total
Balance at Apr. 30, 2017	$ 99,000	$ 850,000	$ 1,736,000	$ (4,140,000)	$ 1,239,000	$ 35,981,000	$ 35,765,000
Balance, shares at Apr. 30, 2017	4,100	8,502,881		3,557,606
Purchases of common stock				$ (10,000)			(10,000)
Purchases of common stock, shares				1,275
Shares given as part of LSDI asset acquisition			198,000	$ 2,000			200,000
Shares given as part of LSDI asset acquisition, shares				(24,097)
Dividend declared at $0.36 per common share outstanding						(1,781,000)	(1,781,000)
Unrealized gain (loss), net of tax effect					1,010,000		1,010,000
Net Income						2,546,000	2,546,000
Balance at Apr. 30, 2018	$ 99,000	$ 850,000	1,934,000	$ (4,148,000)	2,249,000	36,746,000	37,730,000
Balance, shares at Apr. 30, 2018	4,100	8,502,881		3,534,784
Purchases of common stock				$ (79,000)			(79,000)
Purchases of common stock, shares				9,487
Dividend declared at $0.36 per common share outstanding						(1,885,000)	(1,885,000)
Impact of adoption of ASU 2016-01					189,000		189,000
Unrealized gain (loss), net of tax effect					(2,424,000)	2,424,000
Net Income						3,598,000	3,598,000
Balance at Apr. 30, 2019	$ 99,000	$ 850,000	$ 1,934,000	$ (4,227,000)	$ 14,000	$ 40,883,000	$ 39,553,000
Balance, shares at Apr. 30, 2019	4,100	8,502,881		3,544,271