Annual report pursuant to Section 13 and 15(d)

Financial Instruments - Additional Information (Detail)

v3.8.0.1
Financial Instruments - Additional Information (Detail) - USD ($)
1 Months Ended
May 17, 2017
May 31, 2017
Dec. 31, 2017
Mar. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]            
Cash and cash equivalents     $ 29,545,000   $ 12,078,000 $ 19,197,000
Fair market value of warrants         7,114,000  
Acacia Note Warrants [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Fair market value of warrants         $ 507,000  
Warrant exercise price         $ 13.6088  
Primary Warrant [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Fair market value of warrants         $ 8,064,000  
Primary Warrant [Member] | Acacia [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Percentage of warrant exercise 10.00% 10.00%        
Minimum [Member] | Acacia Note Warrants [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Fair market value of warrants     334,000      
Maximum [Member] | Acacia Note Warrants [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Fair market value of warrants     841,000      
Initial Public Offering [Member] | Acacia [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Fair market value of warrants $ 5,790,000          
Percentage of warrant exercise 10.00%          
Initial Public Offering [Member] | Amended Primary Warrant [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Warrant exercise price       $ 13.6088    
Bridge Loan [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Fair market value of warrants     6,534,000      
Cash [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Cash and cash equivalents     8,925,000   9,922,000  
Level 1 [Member] | Money Market Funds [Member]            
Schedule of Available-for-sale Securities [Line Items]            
Cash and cash equivalents     $ 20,620,000   $ 2,156,000