Statements of Income - USD ($)	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Revenue
Product sales	$ 26,182,453	$ 24,410,391	$ 29,894,045
Contract research and development	2,143,743	3,306,887	690,043
Total revenue	28,326,196	27,717,278	30,584,088
Cost of sales	6,078,294	6,616,852	6,019,868
Gross profit	22,247,902	21,100,426	24,564,220
Expenses
Selling, general, and administrative	1,458,598	1,752,962	2,312,076
Research and development	3,344,101	3,061,184	3,000,193
Total expenses	4,802,699	4,814,146	5,312,269
Income from operations	17,445,203	16,286,280	19,251,951
Interest income	1,650,808	1,890,817	2,187,723
Income before taxes	19,096,011	18,177,097	21,439,674
Provision for income taxes	6,147,142	5,884,782	7,071,320
Net income	$ 12,948,869	$ 12,292,315	$ 14,368,354
Net income per share – basic (in dollars per share)	$ 2.68	$ 2.53	$ 2.96
Net income per share – diluted (in dollars per share)	2.68	2.53	2.95
Common Stock, Dividends, Per Share, Declared	$ 4	$ 4	$ 2.06
Weighted average shares outstanding
Basic (in shares)	4,836,602	4,850,209	4,855,504
Diluted (in shares)	4,838,389	4,852,602	4,871,935