Annual report pursuant to Section 13 and 15(d)

Stock Warrants - Schedule of Warrants Outstanding (Detail)

v3.8.0.1
Stock Warrants - Schedule of Warrants Outstanding (Detail) - $ / shares
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Jun. 12, 2015
Aug. 01, 2014
Class of Warrant or Right [Line Items]        
Shares Underlying Outstanding Warrants 36,270,103 27,214,775    
Weighted-average exercise price per share $ 2.74 $ 3.97    
Placement Agent Warrants [Member]        
Class of Warrant or Right [Line Items]        
Shares Underlying Outstanding Warrants 189,126 189,126    
Class A Warrants [Member]        
Class of Warrant or Right [Line Items]        
Shares Underlying Outstanding Warrants   6,880,333    
Representative's Warrant [Member]        
Class of Warrant or Right [Line Items]        
Exercise Prices $ 7.50      
Shares Underlying Outstanding Warrants 206,410 206,410    
Other Warrants [Member]        
Class of Warrant or Right [Line Items]        
Shares Underlying Outstanding Warrants 194,623 258,962    
Exercise Price Less Than or Equal to $2.00 [Member]        
Class of Warrant or Right [Line Items]        
Shares Underlying Outstanding Warrants 16,005,714      
Expiration Start Date Sep. 01, 2021      
Expiration End Date Jul. 25, 2022      
Exercise Price $2.01 - $4.99 [Member]        
Class of Warrant or Right [Line Items]        
Shares Underlying Outstanding Warrants 17,606,105      
Expiration Start Date Jun. 18, 2018      
Expiration End Date Jul. 27, 2021      
Exercise Price $5.00 - $7.99 [Member]        
Class of Warrant or Right [Line Items]        
Shares Underlying Outstanding Warrants 231,409      
Expiration Start Date Apr. 30, 2018      
Expiration End Date Jul. 22, 2019      
Exercise Price Greater Than or Equal to $8.00 [Member]        
Class of Warrant or Right [Line Items]        
Shares Underlying Outstanding Warrants 2,426,875      
Expiration Start Date Jun. 11, 2018      
Expiration End Date Jan. 05, 2022      
Minimum [Member] | Exercise Price $2.01 - $4.99 [Member]        
Class of Warrant or Right [Line Items]        
Exercise Prices $ 2.01      
Minimum [Member] | Exercise Price $5.00 - $7.99 [Member]        
Class of Warrant or Right [Line Items]        
Exercise Prices 5.00      
Minimum [Member] | Exercise Price Greater Than or Equal to $8.00 [Member]        
Class of Warrant or Right [Line Items]        
Exercise Prices 8.00      
Maximum [Member] | Exercise Price Less Than or Equal to $2.00 [Member]        
Class of Warrant or Right [Line Items]        
Exercise Prices 2.00      
Maximum [Member] | Exercise Price $2.01 - $4.99 [Member]        
Class of Warrant or Right [Line Items]        
Exercise Prices 4.99      
Maximum [Member] | Exercise Price $5.00 - $7.99 [Member]        
Class of Warrant or Right [Line Items]        
Exercise Prices $ 7.99      
Note Warrants [Member]        
Class of Warrant or Right [Line Items]        
Exercise Prices       $ 3.00
Shares Underlying Outstanding Warrants 3,315,878 3,315,878   3,321,416
Private Placement [Member]        
Class of Warrant or Right [Line Items]        
Exercise Prices $ 4.65   $ 8.00  
Warrants [Member] | Private Placement [Member]        
Class of Warrant or Right [Line Items]        
Shares Underlying Outstanding Warrants 2,364,066 2,364,066    
2016 Warrants [Member]        
Class of Warrant or Right [Line Items]        
Shares Underlying Outstanding Warrants 14,000,000 14,000,000    
2017 Warrants [Member]        
Class of Warrant or Right [Line Items]        
Shares Underlying Outstanding Warrants 16,000,000