Statements Of Income (USD $)
 3 Months Ended 9 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2012
Dec. 31, 2011
Revenue        
Product sales $ 5,762,925 $ 5,394,758 $ 18,025,002 $ 17,975,331
Contract research and development 762,296 763,768 1,785,920 2,995,590
Total revenue 6,525,221 6,158,526 19,810,922 20,970,921
Cost of sales 1,738,618 2,174,878 5,147,884 7,048,396
Gross profit 4,786,603 3,983,648 14,663,038 13,922,525
Expenses        
Selling, general , and administrative 570,741 520,044 1,714,545 1,742,721
Research and development 501,325 718,688 1,801,609 1,825,159
Total expenses 1,072,066 1,238,732 3,516,154 3,567,880
Income from operations 3,714,537 2,744,916 11,146,884 10,354,645
Interest income 600,395 591,694 1,784,963 1,754,586
Income before taxes 4,314,932 3,336,610 12,931,847 12,109,231
Provision for income taxes 1,415,590 1,047,519 4,211,964 3,825,819
Net income $ 2,899,342 $ 2,289,091 $ 8,719,883 $ 8,283,412
Net income per share - basic $ 0.60 $ 0.48 $ 1.80 $ 1.73
Net income per share - diluted $ 0.60 $ 0.47 $ 1.80 $ 1.71
Weighted average shares outstanding        
Basic 4,847,619 4,807,859 4,832,630 4,786,790
Diluted 4,872,019 4,873,429 4,856,851 4,852,360