Statements of Income (USD $)
 3 Months Ended 9 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2011
Dec. 31, 2010
Revenue        
Product sales $ 5,394,758 $ 6,686,451 $ 17,975,331 $ 19,290,839
Contract research and development 763,768 1,277,057 2,995,590 3,723,123
Total revenue 6,158,526 7,963,508 20,970,921 23,013,962
Cost of sales 2,174,878 2,461,798 7,048,396 7,142,528
Gross profit 3,983,648 5,501,710 13,922,525 15,871,434
Expenses        
Selling, general , and administrative 520,044 638,223 1,742,721 1,901,156
Research and development 718,688 330,681 1,825,159 982,217
Total expenses 1,238,732 968,904 3,567,880 2,883,373
Income from operations 2,744,916 4,532,806 10,354,645 12,988,061
Interest income 591,694 512,203 1,754,586 1,485,664
Income before taxes 3,336,610 5,045,009 12,109,231 14,473,725
Provision for income taxes 1,047,519 1,661,090 3,825,819 4,782,699
Net income $ 2,289,091 $ 3,383,919 $ 8,283,412 $ 9,691,026
Net income per share - basic $ 0.48 $ 0.71 $ 1.73 $ 2.06
Net income per share - diluted $ 0.47 $ 0.70 $ 1.71 $ 2.00
Weighted average shares outstanding        
Basic 4,807,859 4,743,643 4,786,790 4,714,989
Diluted 4,873,429 4,866,617 4,852,360 4,837,963