Statements of Income (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Revenue	$ 6,464,596	$ 6,269,405	$ 19,261,237	$ 20,883,386
Cost of sales	1,263,806	1,169,406	3,701,941	3,918,256
Gross profit	5,200,790	5,099,999	15,559,296	16,965,130
Research and development	771,468	1,126,975	2,671,131	3,087,964
Selling, general, and administrative	327,989	268,905	1,026,448	975,114
Total expenses	1,099,457	1,395,880	3,697,579	4,063,078
Income from operations	4,101,333	3,704,119	11,861,717	12,902,052
Interest income	443,478	457,204	1,358,826	1,325,299
Income before taxes	4,544,811	4,161,323	13,220,543	14,227,351
Provision for income taxes	814,147	739,918	2,060,398	2,578,287
Net income	$ 3,730,664	$ 3,421,405	$ 11,160,145	$ 11,649,064
Net income per share – basic (in dollars per share)	$ 0.77	$ 0.71	$ 2.30	$ 2.41
Net income per share – diluted (in dollars per share)	0.77	0.71	2.30	2.40
Cash dividends declared per common share (in dollars per share)	$ 1	$ 1	$ 3	$ 3
Basic (in shares)	4,846,010	4,845,010	4,846,010	4,843,355
Diluted (in shares)	4,847,436	4,850,507	4,848,506	4,850,120
Product [Member]
Revenue	$ 6,160,967	$ 5,991,241	$ 18,434,039	$ 19,916,864
Contract Research and Development [Member]
Revenue	$ 303,629	$ 278,164	$ 827,198	$ 966,522