Statements of Shareholders' Equity (Unaudited) - USD ($)	Cumulative Effect, Period of Adoption, Adjustment [Member] Common Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Mar. 31, 2021		4,833,232
Balance at Mar. 31, 2021		$ 48,332	$ 19,338,127	$ 1,101,119	$ 50,404,364	$ 70,891,942
Unrealized gain (loss) on marketable securities, net of tax				(90,165)		(90,165)
Net income					3,579,566	3,579,566
Total comprehensive income						3,489,401
Stock-based compensation			7,238			7,238
Cash dividends declared ($1.00 per share of common stock)					(4,833,232)	(4,833,232)
Balance (in shares) at Jun. 30, 2021	4,833,232
Balance at Jun. 30, 2021		$ 48,332	19,345,365	1,010,954	49,150,698	69,555,349
Balance (in shares) at Mar. 31, 2021		4,833,232
Balance at Mar. 31, 2021		$ 48,332	19,338,127	1,101,119	50,404,364	70,891,942
Unrealized gain (loss) on marketable securities, net of tax						(287,199)
Net income						7,226,073
Balance (in shares) at Sep. 30, 2021		4,833,232
Balance at Sep. 30, 2021		$ 48,332	19,402,364	813,920	47,963,973	68,228,589
Balance (in shares) at Jun. 30, 2021	4,833,232
Balance at Jun. 30, 2021		48,332	19,345,365	1,010,954	49,150,698	69,555,349
Unrealized gain (loss) on marketable securities, net of tax				(197,034)		(197,034)
Net income					3,646,507	3,646,507
Total comprehensive income						3,449,473
Stock-based compensation			56,999			56,999
Cash dividends declared ($1.00 per share of common stock)					(4,833,232)	(4,833,232)
Balance (in shares) at Sep. 30, 2021		4,833,232
Balance at Sep. 30, 2021		$ 48,332	19,402,364	813,920	47,963,973	68,228,589
Balance (in shares) at Mar. 31, 2022		4,830,826
Balance at Mar. 31, 2022		$ 48,308	19,256,485	(318,120)	45,578,456	64,565,129	[1]
Unrealized gain (loss) on marketable securities, net of tax				(338,553)		(338,553)
Net income					4,140,116	4,140,116
Total comprehensive income						3,801,563
Stock-based compensation			7,134			7,134
Cash dividends declared ($1.00 per share of common stock)					(4,830,826)	(4,830,826)
Balance (in shares) at Jun. 30, 2022	4,830,826
Balance at Jun. 30, 2022		$ 48,308	19,263,619	(656,673)	44,887,746	63,543,000
Balance (in shares) at Mar. 31, 2022		4,830,826
Balance at Mar. 31, 2022		$ 48,308	19,256,485	(318,120)	45,578,456	64,565,129	[1]
Unrealized gain (loss) on marketable securities, net of tax						(1,465,915)
Net income						10,230,490
Balance (in shares) at Sep. 30, 2022		4,830,826
Balance at Sep. 30, 2022		$ 48,308	19,303,570	(1,784,035)	46,147,293	63,715,136
Balance (in shares) at Jun. 30, 2022	4,830,826
Balance at Jun. 30, 2022		48,308	19,263,619	(656,673)	44,887,746	63,543,000
Unrealized gain (loss) on marketable securities, net of tax				(1,127,362)		(1,127,362)
Net income					6,090,373	6,090,373
Total comprehensive income						4,963,011
Stock-based compensation			39,951			39,951
Cash dividends declared ($1.00 per share of common stock)					(4,830,826)	(4,830,826)
Balance (in shares) at Sep. 30, 2022		4,830,826
Balance at Sep. 30, 2022		$ 48,308	$ 19,303,570	$ (1,784,035)	$ 46,147,293	$ 63,715,136

[1] The March 31, 2021 Balance Sheet is derived from the audited financial statements contained in our Annual Report on Form 10-K for the fiscal year ended March 31, 2021.