Marketable Securities
6 Months Ended
Sep. 30, 2011
Marketable Securities [Abstract] 
Marketable Securities
NOTE 5. MARKETABLE SECURITIES
     Marketable securities with remaining maturities less than one year are classified as short-term, and those with remaining maturities greater than one year are classified as long-term. The fair value of our marketable securities as of September 30, 2011, by maturity, were as follows:
Total <1 Year 1–3 Years 3–5 Years
$ 66,272,362 $ 11,122,455 $ 25,668,319 $ 29,481,588
 
     As of September 30 and March 31, 2011, our marketable securities were as follows:
 
As of September 30, 2011 As of March 31, 2011

Adjusted
Cost		   Gross
Unrealized
Gains		   Gross
Unrealized
Losses		   Fair
Market
Value
Adjusted
Cost		 Gross
Unrealized
Gains		 Gross
Unrealized
Losses		 Fair
Market
Value
U.S. agency
securities
 $ -    $ -    $ -      $ -    $ 83,358    $ 1,200    $ -      $ 84,558
Corporate bonds   43,827,332

937,914

        (437,622 ) 44,327,624 37,884,146 1,231,743 (147,443 ) 38,968,446
Municipal bonds   21,439,498 523,744 (18,504 ) 21,944,738 21,582,084 602,457 (10,047 )   22,174,494
Total $ 65,266,830 $ 1,461,659 $ (456,126 ) $ 66,272,362 $ 59,549,588   $ 1,835,400 $ (157,490 )   $ 61,227,498
 
     The following table shows the gross unrealized losses and fair value of our investments with unrealized losses, aggregated by investment category and length of time that individual securities had been in a continuous unrealized loss position as of September 30 and March 31, 2011:
 
Less Than 12 Months 12 Months or Greater Total
Fair
Market
Value		 Gross
Unrealized
Losses		 Fair
Market
Value		 Gross
Unrealized
Losses		 Fair
Market
Value		 Gross
Unrealized
Losses
As of September 30, 2011
  U.S. agency securities  $ - $ - $ - $ - $ - $ -  
  Corporate bonds 16,276,873 (437,622 ) - - 16,276,873 (437,622 )
  Municipal bonds 1,798,229 (18,504 ) - - 1,798,229 (18,504 )
  Total $ 18,072,102 $ (456,126 ) $ - $ - $ 18,072,102 $ (456,126 )
As of March 31, 2011
U.S. agency securities  $ -   $ -     $ -   $ -     $ -   $ -  
Corporate bonds 9,146,952 (147,443 ) - -   9,146,952 (147,443 )
Municipal bonds 2,178,225   (10,047 )   -   -     2,178,225   (10,047 )
Total $ 11,325,177   $ (157,490 )   $ -   $ -     $ 11,325,177   $ (157,490 )
 
     Gross unrealized losses totaled $456,126 as of September 30, 2011, and were attributable to seven corporate and two municipal bonds out of a portfolio of 54 bonds. Corporate bonds accounted for $437,622 of the total gross unrealized losses. The gross unrealized losses were due to market-price decreases and rating downgrades after the bonds were purchased. None of the bonds we hold had been in a continuous unrealized loss position for 12 months or more. Although several of the bonds we held were downgraded by Moody's or Standard and Poor's during the quarter ended September 30, 2011, all of the bonds that were rated by Moody's or Standard and Poor's had investment-grade credit ratings. For each bond with an unrealized loss, we expect to recover the entire cost basis of each security based on our consideration of factors including their credit ratings, the underlying ratings of insured bonds, and historical default rates for securities of comparable credit rating. Because we expect to recover the entire cost basis of the securities, and because we do not intend to sell the securities and it is not more likely than not that we will be required to sell the securities before recovery of the cost basis, which may be maturity, we did not consider any of our marketable securities to be other-than-temporarily impaired at September 30, 2011.