Statements of Income (USD $)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Revenue
Product sales	$ 24,434,823	$ 25,151,822	$ 26,024,823
Contract research and development	2,598,596	3,427,398	5,172,240
Total revenue	27,033,419	28,579,220	31,197,063
Cost of sales	7,025,181	9,325,511	9,783,698
Gross profit	20,008,238	19,253,709	21,413,365
Expenses
Selling, general , and administrative	2,240,563	2,380,603	2,474,468
Research and development	2,570,821	2,600,058	1,269,127
Total expenses	4,811,384	4,980,661	3,743,595
Income from operations	15,196,854	14,273,048	17,669,770
Interest income	2,359,603	2,350,191	2,021,426
Income before taxes	17,556,457	16,623,239	19,691,196
Provision for income taxes	5,727,619	5,242,144	6,330,251
Net income	$ 11,828,838	$ 11,381,095	$ 13,360,945
Net income per share - basic	$ 2.44	$ 2.37	$ 2.83
Net income per share - diluted	$ 2.43	$ 2.34	$ 2.76
Weighted average shares outstanding
Basic	4,839,810	4,796,227	4,729,035
Diluted	4,863,546	4,863,471	4,844,266