Statements of Income (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Revenue
Revenue	$ 6,269,405	$ 7,360,789	$ 20,883,386	$ 21,964,689
Cost of sales	1,169,406	1,657,700	3,918,256	4,809,235
Gross profit	5,099,999	5,703,089	16,965,130	17,155,454
Expenses
Research and development	1,126,975	852,739	3,087,964	2,788,968
Selling, general, and administrative	268,905	313,033	975,114	1,060,757
Total expenses	1,395,880	1,165,772	4,063,078	3,849,725
Income from operations	3,704,119	4,537,317	12,902,052	13,305,729
Interest income	457,204	404,665	1,325,299	1,154,303
Income before taxes	4,161,323	4,941,982	14,227,351	14,460,032
Provision for income taxes	739,918	1,370,380	2,578,287	4,429,780
Net income	$ 3,421,405	$ 3,571,602	$ 11,649,064	$ 10,030,252
Net income per share – basic (in dollars per share)	$ 0.71	$ 0.74	$ 2.41	$ 2.07
Net income per share – diluted (in dollars per share)	0.71	0.74	2.40	2.07
Cash dividends declared per common share (in dollars per share)	$ 1	$ 1	$ 3	$ 3
Weighted average shares outstanding
Basic (in shares)	4,845,010	4,841,369	4,843,355	4,841,130
Diluted (in shares)	4,850,507	4,847,290	4,850,120	4,846,036
Product [Member]
Revenue
Revenue	$ 5,991,241	$ 6,448,831	$ 19,916,864	$ 19,718,584
Contract Research and Development [Member]
Revenue
Revenue	$ 278,164	$ 911,958	$ 966,522	$ 2,246,105