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Stockholders' Equity - Stock and Warrant Issuances - Additional Information (Detail)
 1 Months Ended 3 Months Ended 12 Months Ended
Oct. 11, 2017
shares
Oct. 10, 2017
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Apr. 02, 2017
USD ($)
Feb. 28, 2018
USD ($)
$ / shares
shares
Nov. 30, 2016
USD ($)
Investor
shares
Oct. 31, 2016
USD ($)
shares
Jun. 30, 2016
USD ($)
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Jul. 31, 2015
USD ($)
shares
Feb. 28, 2015
USD ($)
shares
Oct. 31, 2013
USD ($)
shares
Mar. 31, 2018
$ / shares
shares
Dec. 31, 2017
USD ($)
Investor
$ / shares
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Dec. 31, 2016
USD ($)
$ / shares
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Dec. 31, 2015
USD ($)
$ / shares
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Nov. 30, 2017
USD ($)
Jun. 06, 2016
USD ($)
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Oct. 20, 2015
USD ($)
Dec. 31, 2014
$ / shares
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Stockholders Equity Note [Line Items]                                    
Sale of common stock, net of expenses (in shares)       424,000   2   3,000,000 1 1                
Proceeds from issuance of private placement | $           $ 1,200,000     $ 2,600,000 $ 7,500,000                
Net proceeds from issuance of private placement | $       $ 4,300,000   $ 1,100,000     $ 2,500,000 $ 6,900,000                
Number of warrants outstanding (in shares)                       14,049 78 44       9
Sale of units to underwriter               3,000,000                    
Proceeds of common stock issued, net of related expenses | $               $ 6,000,000                    
Number of pre-funded warrants       76,000                            
Maximum [Member]                                    
Stockholders Equity Note [Line Items]                                    
Warrants exercisable per share price (in dollars per share) | $ / shares                       $ 19,712,000 $ 19,712,000 $ 19,712,000       $ 19,712,000
Maximum offering and selling of stock and securities that entity make to raise capital | $                                 $ 71,800,000  
Valuation using contractual term                     5 years 10 months 13 days 4 years 10 months 17 days            
Valuation using volatility rate                     291.61% 266.92%            
Valuation using risk free rate                     2.63% 2.06%            
Amendment to Restructuring Agreement [Member]                                    
Stockholders Equity Note [Line Items]                                    
Warrants issued to purchase Common Stock 127,551 225                   255            
Warrants exercisable per share price (in dollars per share) | $ / shares                       $ 61,250            
Number of warrants outstanding (in shares)                       10            
Term period for warrants                       4 years 6 months            
Warrants exercised (in shares)                       3            
Number of investors | Investor                       2            
Shares issuable upon warrants exercised                       735            
Warrants exercise price description                       The warrants contain a cashless exercise provision that allows the holders to exercise each warrant for three shares of common stock.            
Securities Purchase Agreement [Member] | Warrant Repurchase Agreements [Member]                                    
Stockholders Equity Note [Line Items]                                    
Aggregate amount to be paid in exchange for cancellation of warrants | $     $ 7,900,000       $ 7,900,000                      
Common Stock Issued [Member]                                    
Stockholders Equity Note [Line Items]                                    
Sale of common stock, net of expenses (in shares)                     668,855   2 4        
Common shares and rights issued                       227,287 10          
Common Stock Issued [Member] | Securities Purchase Agreement [Member]                                    
Stockholders Equity Note [Line Items]                                    
Common shares and rights issued                       224,000            
Senior Secured Convertible Notes [Member] | Securities Purchase Agreement [Member]                                    
Stockholders Equity Note [Line Items]                                    
Debt instrument, principal face amount | $                               $ 35,000,000    
Senior Secured Convertible Notes [Member] | Common Stock Issued [Member] | Securities Purchase Agreement [Member]                                    
Stockholders Equity Note [Line Items]                                    
Common shares and rights issued                       217,800            
Series A Common Stock Warrants [Member]                                    
Stockholders Equity Note [Line Items]                                    
Warrants exercisable per share price (in dollars per share) | $ / shares                       $ 24,500            
Number of warrants outstanding (in shares)                       9,000,000            
Number of warrants converted               8,000,000                    
Gross proceeds from underwriting offering | $               $ 7,000,000                    
Warrants exercised (in shares)                       1,000,000            
Net proceeds from exercise of warrants | $                       $ 400,000            
Series A And B Common Stock Warrants [Member]                                    
Stockholders Equity Note [Line Items]                                    
Value of warrants issued | $               $ 3,400,000                    
Series B Common Stock Warrants [Member]                                    
Stockholders Equity Note [Line Items]                                    
Warrants exercised (in shares)                         1,000,000          
Net proceeds from exercise of warrants | $                         $ 800,000          
Remaining outstanding warrants expired                         3,000,000          
Warrants expiration date                       Jan. 29, 2016            
2013 Warrants [Member]                                    
Stockholders Equity Note [Line Items]                                    
Warrants issued to purchase Common Stock                   9                
Value of warrants issued | $                   $ 1,900,000                
Warrants exercisable per share price (in dollars per share) | $ / shares                       $ 19,712,000            
Number of warrants outstanding (in shares)                       9            
Term period for warrants                       5 years            
February 2015 Warrants [Member]                                    
Stockholders Equity Note [Line Items]                                    
Warrants issued to purchase Common Stock                 9                  
Value of warrants issued | $                 $ 800,000                  
Warrants exercisable per share price (in dollars per share) | $ / shares                       $ 24,500            
Number of warrants outstanding (in shares)                       9            
Term period for warrants                       5 years            
Series C Warrants [Member]                                    
Stockholders Equity Note [Line Items]                                    
Aggregate amount to be paid in exchange for cancellation of warrants | $                       $ 7,876,000 $ 0 $ 0        
Series C Warrants [Member] | Securities Purchase Agreement [Member]                                    
Stockholders Equity Note [Line Items]                                    
Value of warrants issued | $             27,800,000                      
Series C Warrants [Member] | Securities Purchase Agreement [Member] | Warrant Repurchase Agreements [Member]                                    
Stockholders Equity Note [Line Items]                                    
Aggregate amount to be paid in exchange for cancellation of warrants | $             7,900,000                      
Series C Warrants [Member] | Senior Secured Convertible Notes [Member]                                    
Stockholders Equity Note [Line Items]                                    
Debt instrument, principal face amount | $             $ 35,000,000                      
Series C Warrants [Member] | Senior Secured Convertible Notes [Member] | Securities Purchase Agreement [Member]                                    
Stockholders Equity Note [Line Items]                                    
Number of warrants converted             40                      
Shares issuable upon warrants exercised                               40    
October 2016 Warrants [Member]                                    
Stockholders Equity Note [Line Items]                                    
Warrants issued to purchase Common Stock           1                        
Value of warrants issued | $           $ 300,000                        
Warrants exercisable per share price (in dollars per share) | $ / shares                       $ 24,500            
Number of warrants outstanding (in shares)                       1            
Term period for warrants                       5 years            
Net proceeds from exercise of warrants | $                       $ 100,000            
November 2017 Warrants [Member] | Exchange Agreement [Member]                                    
Stockholders Equity Note [Line Items]                                    
Warrants issued to purchase Common Stock         14,049                          
Value of warrants issued | $         $ 14,400,000                   $ 14,400,000      
Warrants exercisable per share price (in dollars per share) | $ / shares                       $ 1,225            
Number of warrants outstanding (in shares)                       14,049            
Term period for warrants                       5 years            
Number of investors | Investor         2                          
February 2018 Warrants [Member]                                    
Stockholders Equity Note [Line Items]                                    
Warrants issued to purchase Common Stock       1,000,000                            
Value of warrants issued | $       $ 18,300,000                            
Warrants exercisable per share price (in dollars per share) | $ / shares                     $ 10.00              
Number of warrants outstanding (in shares)                     1,000,000              
Valuation using exercise price | $ / shares       $ 10.00                            
Valuation using contractual term       6 years                            
Valuation using volatility rate       122.68%                            
Valuation using risk free rate       1.00%