Statements Of Income (USD $)	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenue
Product sales	$ 5,231,332	$ 5,557,299	$ 12,262,077	$ 12,580,573
Contract research and development	591,464	1,041,334	1,023,624	2,231,822
Total revenue	5,822,796	6,598,633	13,285,701	14,812,395
Cost of sales	1,606,913	2,277,926	3,409,266	4,873,518
Gross profit	4,215,883	4,320,707	9,876,435	9,938,877
Expenses
Selling, general , and administrative	607,694	606,847	1,143,804	1,222,677
Research and development	612,258	611,595	1,300,284	1,106,471
Total expenses	1,219,952	1,218,442	2,444,088	2,329,148
Income from operations	2,995,931	3,102,265	7,432,347	7,609,729
Interest income	621,950	597,363	1,184,568	1,162,892
Income before taxes	3,617,881	3,699,628	8,616,915	8,772,621
Provision for income taxes	1,174,998	1,144,535	2,796,374	2,778,300
Net income	$ 2,442,883	$ 2,555,093	$ 5,820,541	$ 5,994,321
Net income per share - basic	$ 0.51	$ 0.53	$ 1.21	$ 1.26
Net income per share - diluted	$ 0.50	$ 0.52	$ 1.19	$ 1.22
Weighted average shares outstanding
Basic	4,825,441	4,776,198	4,825,095	4,776,198
Diluted	4,884,656	4,896,525	4,882,524	4,896,525