Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2016
Accounting Policies [Abstract]  
Fair Value of Stock-Based Compensation Awards

The following weighted-average input assumptions were used in determining the fair value of the Company’s stock options:

 

     December 31,  
     2016      2015      2014  

Volatility

      70.3%        83.9%        104.0%  

Risk-free interest rate

      1.5%        2.1%        2.1%  

Expected life of option

      6.18 years        6.14 years        6.09 years  

Expected dividend yield

      0.0%        0.0%        0.0%  
Net Loss and Number of Shares Used to Calculate Basic and Diluted Net Loss Per Share

The table below reconciles the net loss and the number of shares used to calculate basic and diluted net loss per share for the years ended December 31, 2016, 2015 and 2014, in thousands.

 

     Year ended December 31,  
     2016      2015      2014  

Numerator:

         

Net loss and comprehensive loss

    $ (15,337 )     $ (16,422 )     $ (22,082 ) 

Less: income from change in fair value of warrants

      —          (332 )       (2,141 ) 
  

 

 

     

 

 

     

 

 

  

Net loss attributable to common stockholders used to calculate diluted net loss per share

    $ (15,337 )     $ (16,754 )     $ (24,223 ) 
  

 

 

     

 

 

     

 

 

  

Denominator:

         

Weighted-average shares outstanding - basic

      84,715        82,144        76,955  

Potentially dilutive common shares outstanding:

         

Warrants

      —          707        1,586  
  

 

 

     

 

 

     

 

 

  

Weighted-average shares used to calculate diluted net loss per share

      84,715        82,851        78,541  
  

 

 

     

 

 

     

 

 

  

Basic – net loss per share

    $ (0.18 )     $ (0.20 )     $ (0.29 ) 

Dilutive – net loss per share

    $ (0.18 )     $ (0.20 )     $ (0.31 ) 
Instruments Excluded from Calculation of Diluted Net Loss Per Share

The following instruments were excluded from the calculation of diluted net loss per share because their effects would be antidilutive:

 

     Year ended December 31,  
     2016      2015      2014  

Stock options

      9,236,228        7,052,642        6,383,457  

Restricted stock units

      1,201,159        1,069,100        1,889,267  

Warrants

      1,893,527        2,810,000        6,310,000  
  

 

 

     

 

 

     

 

 

  
     12,330,914        10,931,742        14,582,724