Quarterly report pursuant to Section 13 or 15(d)

Organization and Summary of Significant Accounting Policies - Additional Information (Details)

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Organization and Summary of Significant Accounting Policies - Additional Information (Details) (USD $)
 0 Months Ended 3 Months Ended 6 Months Ended 0 Months Ended
Feb. 11, 2014
Jun. 30, 2014
Jun. 30, 2013
Jun. 30, 2014
Jun. 30, 2013
Dec. 31, 2013
Feb. 12, 2014
IPO
Feb. 12, 2014
IPO
Underwriter Option
Class Of Stock [Line Items]                
Stock issued during period, shares, reverse stock splits 0.0387              
Common stock shares, issued       50,583     3,682,900 182,900
Common stock share issue price under IPO, per share price             $ 5.75  
Proceeds from issuance of common stock       $ 15,369,000     $ 15,400,000  
Underwriting discounts and other offering costs             5,800,000  
Net loss   (13,239,000) (3,066,000) (17,952,000) (6,600,000)      
Cash used in operations       (8,405,000) (3,661,000)      
Accumulated deficit   (157,875,000)   (157,875,000)   (139,923,000)    
Debt instrument, payment terms       As discussed further in Note 7, the Company refinanced its long-term debt and entered into a term loan with Hercules Technology Growth Capital, Inc. (“Hercules Technology”), as administrative and collateral agent for the lenders thereunder and as lender, and Hercules Technology III, LP, as lender (the “Hercules Term Loan”). The Hercules Term Loan has a financial and liquidity covenant that requires the Company to maintain a cash balance in excess of $6.0 million prior to August 15th and a cash balance of $9.0 million thereafter.        
Cash   $ 11,600,000   $ 11,600,000