Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.2
Description of Business and Basis of Preparation - Additional Information (Detail) - USD ($)
Jun. 30, 2019
Sep. 14, 2018
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]    
Shelf registration maximum equity offering price $ 167,100,000 $ 175,000,000
Number of warrants issued to purchase common stock (in shares)   13,198,075
Aggregate amount receivable upon exercise of warrants   $ 28,600,000
Warrants, expiration date   Mar. 14, 2019
Sales Agreement | Common Stock    
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]    
Shelf registration maximum equity offering price   $ 25,000,000
June 2016 Public Offering    
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]    
Number of warrants issued to purchase common stock (in shares)   4,218,750
Exercise price of warrants (in dollars per share)   $ 3.00
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)   13,198,075
Exercise price of warrants (in dollars per share)   $ 1.85
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)   7,988,175
Exercise price of warrants (in dollars per share)   $ 2.00