MARKETABLE SECURITIES (Tables)
 12 Months Ended
Dec. 31, 2016
Cash and Cash Equivalents [Abstract]  
Summary of Available-for-Sale Marketable Securities

The following is a summary of available-for-sale marketable securities at December 31, 2015 and 2016:

 

     As at December 31, 2016  
     Amortized
cost		      Gross
unrealized
gains		      Gross
unrealized
losses		      Fair
value		  

Available-for-sale—matures within one year:

            

Corporate bonds

    $ 9,456      $ 4      $ (15 )     $ 9,445  
  

 

 

     

 

 

     

 

 

     

 

 

  
     9,456        4        (15 )       9,445  

Available-for-sale—matures after one year through five years:

            

Government bonds

      501        —          (4 )       497  

Corporate bonds

      52,490        3        (567 )       51,926  
  

 

 

     

 

 

     

 

 

     

 

 

  
     52,991        3        (571 )       52,423  

Total

    $ 62,447      $ 7      $ (586 )     $ 61,868  
  

 

 

     

 

 

     

 

 

     

 

 

  

 

     As at December 31, 2015  
     Amortized
cost		      Gross
unrealized
gains		      Gross
unrealized
losses		      Fair
value		  

Available-for-sale—matures within one year:

            

Certificate of deposits

    $ 1      $ —        $ —        $ 1  

Corporate bonds

      9,257        1        (50 )       9,208  
  

 

 

     

 

 

     

 

 

     

 

 

  
     9,258        1        (50 )       9,209  

Available-for-sale—matures after one year through three years: :

            

Corporate bonds

      39,501        —          (444 )       39,057  
  

 

 

     

 

 

     

 

 

     

 

 

  
     39,501        —          (444 )       39,057  

Total

    $ 48,759      $ 1      $ (494 )     $ 48,266  
  

 

 

     

 

 

     

 

 

     

 

 

  
Summary of Gross Unrealized Losses and Fair Values on Investments

The following table presents gross unrealized losses and fair values for those investments that were in an unrealized loss position as of December 31, 2015 and 2016, and the length of time that those investments have been in a continuous loss position:

 

     Less than 12 months      12 months or greater  
     Fair
Value		      Gross
unrealized
loss		      Fair
Value		      Gross
unrealized
loss		  

As of December 31, 2016

    $ 48,663      $ (557 )     $ 4,875      $ (29 ) 

As of December 31, 2015

    $ 32,695      $ (389 )     $ 14,488      $ (105 ) 
Summary of Gross Realized Gain and Loss from Sale of Available-for-Sale Marketable Securities

The following table presents gross realized gains and losses from sale of available-for-sale marketable securities:

 

     Year ended
December 31,		  
     2014      2015      2016  

Gross realized gains from sale of available-for-sale marketable securities

    $ 99      $ 4      $ 24  

Gross realized losses from sale of available-for-sale marketable securities

    $ (93 )     $ (82 )     $ (33 )