Quarterly report pursuant to Section 13 or 15(d)

Description of Business and Basis of Preparation - Additional Information (Detail)

v3.20.2
Description of Business and Basis of Preparation - Additional Information (Detail)
3 Months Ended 6 Months Ended
Jul. 17, 2020
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Jul. 16, 2020
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Jun. 30, 2020
USD ($)
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Apr. 10, 2020
USD ($)
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Apr. 09, 2020
USD ($)
Dec. 12, 2019
USD ($)
$ / shares
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Sep. 14, 2018
USD ($)
$ / shares
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Jun. 30, 2020
USD ($)
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Jun. 30, 2019
USD ($)
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Jun. 30, 2020
USD ($)
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Jun. 30, 2019
USD ($)
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Mar. 31, 2020
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Dec. 31, 2019
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Mar. 31, 2019
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Dec. 31, 2018
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Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Accumulated deficit | $     $ (284,811,000)         $ (284,811,000)   $ (284,811,000)     $ (271,428,000)    
Cash and cash equivalents | $     34,021,000         34,021,000   34,021,000     41,920,000    
Short-term investments | $     3,594,000         3,594,000   3,594,000     $ 6,494,000    
Shelf registration maximum equity offering price | $     $ 124,800,000       $ 175,000,000.0                
Number of warrants issued to purchase common stock (in shares)             1,319,807                
Aggregate amount receivable upon exercise of warrants | $             $ 28,600,000                
Warrants, expiration date             Mar. 14, 2019                
Common stock issued, net of expenses | $               $ 2,463,000 $ 4,046,000 $ 2,669,000 $ 6,556,000        
Common stock, shares authorized (in shares)     100,000,000         100,000,000   100,000,000     100,000,000    
Common stock, shares issued (in shares)     10,478,927         10,478,927   10,478,927     9,741,372    
Common stock, shares outstanding (in shares)     10,478,927         10,478,927   10,478,927     9,741,372    
Subsequent Event                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Reverse stock split, ratio   0.1                          
Common stock, shares authorized (in shares) 100,000,000 250,000,000                          
Common stock, shares issued (in shares) 10,508,302 105,083,291                          
Common stock, shares outstanding (in shares) 10,508,302 105,083,291                          
Stock issued during period as result of reverse stock splits 0 0                          
New Jersey Technology Business Tax Certificate Transfer (NOL) Program                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Maximum selling value of unused net operating losses and research and development tax credit to profitable tax payers. | $                   $ 15,000,000          
Income tax benefit from sale of unused net operating losses and research and development tax credit | $               $ 3,100,000   $ 3,100,000          
Amount received from the program | $     $ 9,800,000                        
Option to Purchase Common Stock                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Options expiration date           2020-01                  
Common Stock                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Common stock issued, net of expenses (in shares)               303,038 266,090 331,565 488,747        
Common stock issued, net of expenses | $               $ 0 $ 0 $ 0 $ 0        
Common stock, shares outstanding (in shares)     10,478,927         10,478,927 5,452,011 10,478,927 5,452,011 9,787,604 9,741,372 5,023,242 4,797,198
Sales Agreement | Common Stock                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Shelf registration maximum equity offering price | $             $ 25,000,000.0                
June 2016 Public Offering                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Number of warrants issued to purchase common stock (in shares)             421,869                
Exercise price of warrants (in dollars per share) | $ / shares             $ 30.00                
March 2018 Public Offering | Series 1 Warrant                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Number of warrants issued to purchase common stock (in shares)             1,319,807                
Exercise price of warrants (in dollars per share) | $ / shares             $ 18.50                
March 2018 Public Offering | Series 2 Warrant                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Number of warrants issued to purchase common stock (in shares)             798,810                
Exercise price of warrants (in dollars per share) | $ / shares             $ 20.00                
December 2019 Public Offering                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Number of warrants issued to purchase common stock (in shares)           3,888,888                  
Common stock issued, net of expenses (in shares)           3,888,888                  
Share price (in dollars per share) | $ / shares           $ 9.00                  
Common stock issued, net of expenses | $           $ 32,500,000                  
Underwriters | Warrant liability                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Number of warrants issued to purchase common stock (in shares)           583,333                  
Number of warrants exercised           583,333                  
Maximum | Option to Purchase Common Stock                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Number of options not exercised           583,333                  
Maximum | Underwriters                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Option to purchase shares of common stock           583,333                  
April 2020 Note Purchase Agreement | 6.0% Senior Convertible Notes due 2026                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Date of issuance and sale of notes         Apr. 09, 2020                    
Face amount | $         $ 10,000,000.0                    
Interest rate         6.00%                    
Aspire Capital | Common Stock Purchase Agreement                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Sale of common stock at sole discretion | $       $ 20,000,000.0                      
Number of purchase aggregate shares of common stock       1,956,547                      
Percentage of common stock outstanding       19.99%                      
Aspire Capital | Common Stock Purchase Agreement | Maximum                              
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]                              
Sale of common stock at sole discretion | $       $ 20,000,000.0                      
Percentage of common stock outstanding       19.99%