Loan Agreements - Additional Information (Detail)
1 Months Ended 6 Months Ended 12 Months Ended
Apr. 10, 2015
shares
Jan. 08, 2015
USD ($)
Tranches
$ / shares
shares
Jan. 31, 2015
USD ($)
Aug. 31, 2012
USD ($)
Mar. 31, 2012
USD ($)
Dec. 31, 2011
USD ($)
$ / shares
shares
Aug. 31, 2012
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Dec. 15, 2015
USD ($)
Nov. 24, 2015
USD ($)
Apr. 30, 2014
shares
Aug. 31, 2013
Debt Instrument [Line Items]                            
Principal outstanding under the Term Loan               $ 20,324,000            
Proceeds from sale of common stock               2,628,000 $ 140,000 $ 35,000        
Unamortized deferred financing costs               200,000            
Unamortized discount on debt, relating to warrants               500,000            
Proceeds from loan payable               21,000,000            
Debt instrument stated interest rate                           7.00%
Accrued interest               $ 136,000 574,000          
Common Stock [Member]                            
Debt Instrument [Line Items]                            
Issuance of Common Stock, shares | shares 6,716,000                          
Hercules Loan Agreement [Member] | Term Loan [Member]                            
Debt Instrument [Line Items]                            
Prior written notice period to prepay term loan               7 days            
Loan and Security Agreement with Lighthouse Capital [Member]                            
Debt Instrument [Line Items]                            
Accrued interest                 $ 574,000          
Loan and Security Agreement with Lighthouse Capital [Member] | Loans payable [Member]                            
Debt Instrument [Line Items]                            
Loan and security agreement, maximum borrowing capacity           $ 10,000,000                
Unamortized discount on debt, relating to warrants     $ 200,000                      
Proceeds from loan payable       $ 5,000,000 $ 5,000,000   $ 10,000,000              
Loan and security agreement, borrowings repayment period           36 months                
Debt instrument stated interest rate           8.25%                
Loan and security agreement, borrowings repayment start date           Dec. 01, 2012                
Line of credit facility, additional interest payment               $ 600,000            
Repayments of notes payable     3,600,000                      
Loan and Security Agreement with Lighthouse Capital [Member] | Loans payable [Member] | Series D Convertible Preferred Stock [Member]                            
Debt Instrument [Line Items]                            
Exercise price of warrant | $ / shares           $ 12.04                
Warrant expiration date           2021-12                
Warrant expiration period           10 years                
Loan and Security Agreement with Lighthouse Capital [Member] | Loans payable [Member] | Common Stock [Member]                            
Debt Instrument [Line Items]                            
Warrant to purchase stock, number of securities called by warrants or rights | shares                         66,436  
Loan and Security Agreement with Lighthouse Capital [Member] | Maximum [Member] | Loans payable [Member] | Series D Convertible Preferred Stock [Member]                            
Debt Instrument [Line Items]                            
Warrant to purchase stock, number of securities called by warrants or rights | shares           66,436                
Hercules Technology Growth Capital, Inc. [Member] | Hercules Loan Agreement [Member] | Stock Purchase Agreement [Member]                            
Debt Instrument [Line Items]                            
Issuance of Common Stock, shares | shares   135,501                        
Issuance/sale of stock, price per share | $ / shares   $ 7.38                        
Proceeds from sale of common stock   $ 1,000,000                        
Hercules Technology Growth Capital, Inc. [Member] | Hercules Loan Agreement [Member] | Term Loan [Member]                            
Debt Instrument [Line Items]                            
Loan and security agreement, maximum borrowing capacity   $ 26,000,000                        
Principal outstanding under the Term Loan               $ 21,000,000            
Term loan facility, maturity date   Jul. 01, 2018                        
Term loan facility, interest rate terms               The Term Loan will mature on July 1, 2018. Each advance under the Term Loan accrues interest at a floating per annum rate equal to the greater of (i) 7.30% or (ii) the sum of 7.30% plus the prime rate minus 5.75%. The Term Loan provided for interest-only payments on a monthly basis until December 31, 2015.            
Additional interest rate during an event of default   5.00%                        
Term loan facility, interest rate   7.30%                        
Debt prepayment charge, after twelve months   2.00%                        
Debt prepayment charge, after twenty-four months   1.00%                        
Final payment as percentage of aggregate original principal amount   6.70%                        
Class of warrant or right, date until which warrants exercisable   Jan. 08, 2020                        
Estimated fair value of warrant     $ 824,000                      
Hercules Technology Growth Capital, Inc. [Member] | Hercules Loan Agreement [Member] | Term Loan [Member] | Common Stock [Member]                            
Debt Instrument [Line Items]                            
Exercise price of warrant | $ / shares   $ 6.05                        
Warrant to purchase stock, number of securities called by warrants or rights | shares   171,901                        
Hercules Technology Growth Capital, Inc. [Member] | Hercules Loan Agreement [Member] | Term Loan [Member] | Prime Rate [Member]                            
Debt Instrument [Line Items]                            
Term loan facility, interest rate spread   5.75%                        
Hercules Technology Growth Capital, Inc. [Member] | Hercules Loan Agreement [Member] | Term Loan [Member] | Borrowing One [Member]                            
Debt Instrument [Line Items]                            
Loan and security agreement, maximum borrowing capacity   $ 15,000,000                        
Hercules Technology Growth Capital, Inc. [Member] | Hercules Loan Agreement [Member] | Term Loan [Member] | Second Tranche [Member]                            
Debt Instrument [Line Items]                            
Loan and security agreement, maximum borrowing capacity                       $ 6,000,000    
Hercules Technology Growth Capital, Inc. [Member] | Hercules Loan Agreement [Member] | Term Loan [Member] | Up on Meeting Certain Clinical Milestone on or Prior to Dec. 15, 2015 [Member]                            
Debt Instrument [Line Items]                            
Loan and security agreement, maximum borrowing capacity                     $ 5,000,000      
Hercules Technology Growth Capital, Inc. [Member] | Hercules Loan Agreement [Member] | Term Loan [Member] | Maximum [Member]                            
Debt Instrument [Line Items]                            
Number of tranches | Tranches   3