Loan Agreements (Tables)
12 Months Ended
Dec. 31, 2015
Debt Instrument [Line Items]  
Summary of Minimum Future Principal Payments

The minimum future principal payments are as follows (in thousands):

Year Ending December 31,

 

 

 

 

2016

 

$

7,945

 

2017

 

 

8,544

 

2018

 

 

4,511

 

Unamortized discount relating to warrants and deferred financing costs

 

 

(676

)

Total

 

 

20,324

 

Less current portion

 

 

(7,652

)

Long-term portion

 

$

12,672

 

 

Fair Value of Stock Warrants Calculated using Black-Scholes Assumptions

The Company’s warrants were valued using the Black-Scholes option-pricing model.  The fair values were derived by applying the following assumptions:

 

 

 

December 31, 2013

Expected life

 

4-8 years

Risk-free interest rate

 

2.90%

Expected volatility

 

64%-84%

Expected dividend rate

 

%

 

Hercules Loan Agreement [Member] | Common Stock Warrants [Member]  
Debt Instrument [Line Items]  
Fair Value of Stock Warrants Calculated using Black-Scholes Assumptions

The following table shows the Black-Scholes assumptions used to value the warrant:

 

 

January 8, 2015

 

Contractual life

 

5 years

 

Volatility rate

 

 

61

%

Risk-free interest rate

 

 

1.5

%

Expected dividends