Annual report pursuant to Section 13 and 15(d)

CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details 1)

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CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details 1)
$ in Thousands
 12 Months Ended
Dec. 31, 2015
USD ($)
item
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Dec. 31, 2012
USD ($)
Cash, cash equivalents and short term investments.        
Cash and cash equivalents $ 43,456 $ 15,203 $ 20,854 $ 33,484
Short-term Investments 82,820 127,956    
Cash, cash equivalents and short-term investments 126,276 143,159    
Available-For-Sale Securities Reconciliation        
Amortized Cost 97,911 132,964    
Gross Unrealized Gains 12 25    
Gross Unrealized Losses (56) (32)    
Fair Value 97,867 132,957    
Years to Maturity        
Within one year 93,572      
After One Year Through Two Years $ 4,295      
Weighted-average time to maturity of cash equivalents and available-for-sale securities 118 days      
Proceeds from sale of short term investments     $ 16,479  
Number of investments in continuous unrealized loss position for more than twelve months | item 0      
Fair value and gross unrealized losses of investments in individual securities in unrealized loss position        
Number of individual securities in unrealized loss position for twelve months or less | item 43      
Fair Value $ 67,386      
Unrealized Losses (56)      
Money Market Funds        
Cash, cash equivalents and short term investments.        
Cash, cash equivalents and short-term investments 26,291 10,027    
U S Treasury Securities        
Cash, cash equivalents and short term investments.        
Cash, cash equivalents and short-term investments 9,048 2,010    
Available-For-Sale Securities Reconciliation        
Amortized Cost 9,061 2,010    
Gross Unrealized Losses (13)      
Fair Value 9,048 2,010    
Years to Maturity        
Within one year 4,753      
After One Year Through Two Years 4,295      
Fair value and gross unrealized losses of investments in individual securities in unrealized loss position        
Fair Value 8,294      
Unrealized Losses (13)      
U S Government Sponsored Enterprises Debt Securities        
Cash, cash equivalents and short term investments.        
Cash, cash equivalents and short-term investments 48,613 45,786    
Available-For-Sale Securities Reconciliation        
Amortized Cost 48,643 45,793    
Gross Unrealized Gains 1 4    
Gross Unrealized Losses (31) (11)    
Fair Value 48,613 45,786    
Years to Maturity        
Within one year 48,613      
Fair value and gross unrealized losses of investments in individual securities in unrealized loss position        
Fair Value 41,266      
Unrealized Losses (31)      
Corporate Bond Securities And Commercial Paper        
Cash, cash equivalents and short term investments.        
Cash, cash equivalents and short-term investments 40,206 85,161    
Available-For-Sale Securities Reconciliation        
Amortized Cost 40,207 85,161    
Gross Unrealized Gains 11 21    
Gross Unrealized Losses (12) (21)    
Fair Value 40,206 85,161    
Years to Maturity        
Within one year 40,206      
Fair value and gross unrealized losses of investments in individual securities in unrealized loss position        
Fair Value 17,826      
Unrealized Losses (12)      
Demand Deposits        
Cash, cash equivalents and short term investments.        
Cash, cash equivalents and short-term investments $ 2,118 $ 175