Common and Preferred Stock (Tables)
12 Months Ended
Dec. 31, 2015
Stockholders' Equity, Number of Shares, Par Value and Other Disclosures [Abstract]  
Schedule of common stock reserved for issuance
The Company’s shares of common stock reserved for issuance as of December 31, 2014 and 2015 were as follows:
 
2014
   
 
2015
Series A convertible preferred stock
2,383,745

 
 

Series B convertible preferred stock
3,649,368

 
 

Series C convertible preferred stock
5,406,501

 
 

Series D convertible preferred stock
3,409,210

 
 

Lender Warrants and Additional Lender Warrant to purchase common stock
150,000

(1) 
 
200,000

Stock options outstanding
3,425,117

(1) 
 
4,297,893

Possible future issuance under equity incentive plan

 
 
1,521,843

Possible future issuance under employee stock purchase plan

 
 
241,272

Total shares reserved
18,423,941

 
 
6,261,008

 
(1)
As described in Note 10, as of December 31, 2014, the Company had exceeded its common shares authorized when considering the number of possible shares that may be issuable after consideration of all existing instruments that could be settled in shares. On February 10, 2015, the Company increased its number of authorized common shares to 25,000,000. Those instruments which had been accounted for as liabilities were reclassified to equity as of that date.