Statements of Income (Unaudited) - USD ($)
 3 Months Ended 9 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2015
Dec. 31, 2014
Revenue        
Product sales $ 5,025,041 $ 5,883,690 $ 19,197,578 $ 22,345,577
Contract research and development 990,974 408,058 2,419,113 666,579
Total revenue 6,016,015 6,291,748 21,616,691 23,012,156
Cost of sales 1,508,361 1,473,655 5,146,803 4,641,633
Gross profit 4,507,654 4,818,093 16,469,888 18,370,523
Expenses        
Selling, general, and administrative 406,676 533,695 1,416,071 1,788,944
Research and development 738,657 694,758 2,048,620 2,285,465
Total expenses 1,145,333 1,228,453 3,464,691 4,074,409
Income from operations 3,362,321 3,589,640 13,005,197 14,296,114
Interest income 468,367 557,843 1,422,696 1,669,320
Income before taxes 3,830,688 4,147,483 14,427,893 15,965,434
Provision for income taxes 1,253,237 1,354,577 4,736,421 5,259,796
Net income $ 2,577,451 $ 2,792,906 $ 9,691,472 $ 10,705,638
Net income per share – basic (in dollars per share) $ 0.53 $ 0.57 $ 2 $ 2.21
Net income per share – diluted (in dollars per share) 0.53 $ 0.57 2 $ 2.20
Cash dividends declared per common share (in dollars per share) $ 1 $ 3
Weighted average shares outstanding        
Basic (in shares) 4,844,845 4,857,953 4,853,970 4,854,702
Diluted (in shares) 4,846,970 4,876,074 4,857,103 4,871,270