Statements of Income (USD $)	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Revenue
Product sales	$ 25,151,822	$ 26,024,823	$ 22,665,860
Contract research and development	3,427,398	5,172,240	5,481,325
Total revenue	28,579,220	31,197,063	28,147,185
Cost of sales	9,325,511	9,783,698	8,313,015
Gross profit	19,253,709	21,413,365	19,834,170
Expenses
Selling, general , and administrative	2,380,603	2,474,468	2,414,584
Research and development	2,600,058	1,269,127	1,121,050
Total expenses	4,980,661	3,743,595	3,535,634
Income from operations	14,273,048	17,669,770	16,298,536
Interest income	2,350,191	2,021,426	1,617,880
Income before taxes	16,623,239	19,691,196	17,916,416
Provision for income taxes	5,242,144	6,330,251	5,917,072
Net income	$ 11,381,095	$ 13,360,945	$ 11,999,344
Net income per share - basic	$ 2.37	$ 2.83	$ 2.56
Net income per share - diluted	$ 2.34	$ 2.76	$ 2.47
Weighted average shares outstanding
Basic	4,796,227	4,729,035	4,692,496
Diluted	4,863,471	4,844,266	4,857,044