Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Additional Information (Detail)

v3.10.0.1
Financial Instruments - Additional Information (Detail) - USD ($)
 1 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2018
Apr. 30, 2018
May 31, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]            
Aggregate fair value held securities unrealized loss position for less than 12 months $ 25,500,000     $ 25,500,000    
Aggregate fair value held securities unrealized loss position for greater than 12 months $ 0     $ 0    
Marketable securities maturity period       2 years    
Warrants to purchase common stock 1,297,151     1,297,151   1,524,573
Change in fair value of warrant liability       $ 15,000 $ (7,114,000)  
Financial instruments fair value transfers between Level 1, Level 2 or Level 3 $ 0     0    
April 2018 Warrant [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Warrants maturity period   5 years        
Warrant exercise price   $ 11.73        
Warrants to purchase common stock   20,000        
Convertible Notes Payable [Member] | Acacia [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Number of warrants issued           3
Warrants maturity period           4 years
Primary Warrant [Member] | Acacia [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Warrants maturity period           5 years
Primary Warrant [Member] | Acacia [Member] | Initial Public Offering [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Warrant exercise price     $ 13.6088      
Amended Primary and Acacia Note Warrants [Member] | Initial Public Offering [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Warrant exercise price         $ 13.6088  
10% Warrant [Member] | Acacia [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Warrants maturity period     5 years      
Warrant exercise price     $ 13.6088      
Warrants to purchase common stock     809,400      
10% Warrant [Member] | Acacia [Member] | Fair Value, Inputs, Level 3 [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Fair value of warrant     $ 5,790,000      
April 2018 Warrant [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Fair value of warrant 222,000     $ 222,000    
Change in fair value of warrant liability $ 15,000