Fair Value Measurements (Tables)
 12 Months Ended
Dec. 31, 2015
Fair Value Disclosures [Abstract]  
Schedule of Assets Measured or Disclosed at Fair Value on Recurring Basis

A summary of the Company’s assets that are measured or disclosed at fair value on a recurring basis as of December 31, 2015 and 2014 are presented below:

 

Description

    At December 31,
2015		      (Level 1)      (Level 2)      (Level 3)  

Cash equivalents

            

Money market fund

    $ 45,557       $ 45,557       $ —        $ —    

Held-to-maturity investments

            

U.S. treasury securities

      38,504         —          38,504         —    

Assets held in restriction

            

Money market fund

      1,116         —          1,116         —    
  

 

 

     

 

 

     

 

 

     

 

 

  

Total

    $ 85,177       $ 45,557       $ 39,620       $ —    
  

 

 

     

 

 

     

 

 

     

 

 

  

Description

    At December 31,
2014		      (Level 1)      (Level 2)      (Level 3)  

Cash equivalents

            

Money market fund

    $ 20,425       $ 20,425       $ —        $ —    

Held-to-maturity investments

            

U.S. treasury securities and government agency bonds

      72,532         —          72,532         —    

Assets held in restriction

            

Money market fund and certificate of deposit

      1,380         —          1,380         —    
  

 

 

     

 

 

     

 

 

     

 

 

  

Total

    $ 94,337       $ 20,425       $ 73,912       $ —    
  

 

 

     

 

 

     

 

 

     

 

 

  
Schedule of Roll-Forward of Company's Liabilities Measured at Fair Value on Recurring Basis Using Unobservable Inputs (Level 3)

The fair value of the preferred stock warrant prior to the closing of the IPO was based significantly on the fair value of the preferred stock, which was developed using unobservable inputs, and was classified within Level 3. The following table provides a roll-forward of the Company’s liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3):

 

BALANCE—January 1, 2013

      331   

Issuance of preferred stock warrants

      324   

Change in fair value of warrant liability

      (126 ) 
  

 

 

  

BALANCE—December 31, 2013

      529   

Change in fair value of warrant liability

      2,559   

Transfers to Level 2

      (3,088 ) 
  

 

 

  

BALANCE—December 31, 2014

    $ —