Statements of Income (Unaudited) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue
Revenue	$ 6,501,945	$ 7,506,075	$ 12,796,641	$ 14,613,981
Cost of sales	1,346,098	1,352,845	2,438,135	2,748,850
Gross profit	5,155,847	6,153,230	10,358,506	11,865,131
Expenses
Research and development	926,596	971,963	1,899,663	1,960,989
Selling, general, and administrative	368,450	377,448	698,459	706,209
Total expenses	1,295,046	1,349,411	2,598,122	2,667,198
Income from operations	3,860,801	4,803,819	7,760,384	9,197,933
Interest income	456,309	443,325	915,348	868,095
Income before taxes	4,317,110	5,247,144	8,675,732	10,066,028
Provision for income taxes	495,048	964,534	1,246,251	1,838,369
Net income	$ 3,822,062	$ 4,282,610	$ 7,429,481	$ 8,227,659
Net income per share – basic (in dollars per share)	$ 0.79	$ 0.88	$ 1.53	$ 1.70
Net income per share – diluted (in dollars per share)	0.79	0.88	1.53	1.70
Cash dividends declared per common share (in dollars per share)	$ 1	$ 1	$ 2	$ 2
Weighted average shares outstanding
Basic (in shares)	4,846,010	4,843,032	4,846,010	4,842,524
Diluted (in shares)	4,847,881	4,852,644	4,849,357	4,851,072
Product [Member]
Revenue
Revenue	$ 6,187,708	$ 7,054,977	$ 12,273,072	$ 13,925,623
Contract Research and Development [Member]
Revenue
Revenue	$ 314,237	$ 451,098	$ 523,569	$ 688,358