Cash, Cash Equivalents, and Marketable Securities
 6 Months Ended
Jun. 30, 2012
Cash, Cash Equivalents, and Marketable Securities [Abstract]  
Cash, Cash Equivalents, and Marketable Securities

4. Cash, Cash Equivalents, and Marketable Securities

The following is a summary of cash, cash equivalents, restricted cash, and marketable securities as of the respective dates (in thousands):

 

                                 
    June 30, 2012  
    Amortized
Cost		     Unrealized
Gains		     Unrealized
Losses		     Estimated
Fair Value		  

Cash

   $ 1,083     $ —       $ —       $ 1,083  

Certificates of deposit

     200       —         —         200  

Money market funds

     7,408       —         —         7,408  

U.S. Treasury securities

     83,744       —         (2 )      83,742  
   

 

 

    

 

 

    

 

 

    

 

 

  
    $ 92,435     $ —       $ (2 )    $ 92,433  
   

 

 

    

 

 

    

 

 

    

 

 

  
   
    December 31, 2011  
    Amortized
Cost		     Unrealized
Gains		     Unrealized
Losses		     Estimated
Fair Value		  

Cash

   $ 1,421     $ —       $ —       $ 1,421  

Certificates of deposit

     200       —         —         200  

Money market funds

     9,238       —         —         9,238  

U.S. Treasury securities

     51,674       29       —         51,703  
   

 

 

    

 

 

    

 

 

    

 

 

  
    $ 62,533     $ 29     $ —       $ 62,562  
   

 

 

    

 

 

    

 

 

    

 

 

  

There were no sales of available-for-sale marketable securities during the first six months of 2012 or 2011. The amortized cost and estimated fair value of available-for-sale marketable securities at June 30, 2012 and December 31, 2011 were as follows (in thousands):

 

                                 
    June 30, 2012     December 31, 2011  
    Cost     Fair value     Cost     Fair value  

Marketable securities

     83,744       83,742       51,674       51,703  
   

 

 

    

 

 

    

 

 

    

 

 

  

Based on the fair value of the Company’s marketable securities at June 30, 2012, $5.1 million had a maturity of between one and two years, and the remaining $78.7 million had maturities of one year or less.