Quarterly report pursuant to Section 13 or 15(d)

Redeemable Preferred Stock and Stockholders' Equity - Additional Information (Detail)

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Redeemable Preferred Stock and Stockholders' Equity - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Jul. 23, 2020
Jul. 23, 2020
Jul. 22, 2020
Jun. 10, 2020
Jul. 31, 2020
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Jun. 30, 2020
Dec. 31, 2019
Temporary Equity And Stockholders Equity [Line Items]                      
Common stock, shares authorized           180,000,000   180,000,000     40,000,000
Series F Preferred stock, shares issued           1,000   1,000     0
Common stock value           $ 93,000   $ 93,000     $ 31,000
Proceeds from offering, net of underwriting discounts and commissions     $ 16,100,000   $ 8,000,000            
Warrants issued in connection with debt instruments               $ 67,000 $ 209,000    
Expected term (years)             6 years 1 month 6 days 5 years 6 months 6 years 1 month 6 days    
Volatility             85.40% 102.80% 85.40%    
Risk-free interest rate             2.60% 0.37% 2.60%    
Change in fair value of warrants               $ (5,850,000)      
Issuance costs for common stock warrants               1,640,000      
Deemed dividend on convertible preferred stock           $ 17,378,000   $ 17,378,000      
Series E Preferred stock, shares authorized           1,000,000   1,000,000     1,000,000
Series E Preferred stock, par value           $ 0.001   $ 0.001     $ 0.001
Series E Preferred stock, shares issued           0   0     70,000
Series E Preferred stock, shares outstanding           0   0     70,000
Compensation expense related to stock options           $ 800,000 $ 800,000 $ 2,400,000 $ 1,900,000    
Total unrecognized compensation expense           $ 1,400,000   $ 1,400,000      
Unrecognized share based compensation expense to be recognized over weighted-average period           1 year 2 months 12 days          
Warrant expiration date       Jun. 10, 2025              
Proceeds from offering       $ 6,900,000              
Combined purchase price of share and warrant       $ 0.64              
Other offering expenses       $ 700,000              
Outstanding stock options, RSUs and warrants excluded from diluted loss per share           67,200,000 5,600,000 67,200,000 5,600,000    
June 2020 Warrants                      
Temporary Equity And Stockholders Equity [Line Items]                      
Proceeds of common stock and warrants               $ 6,200,000      
Exercise price of warrants           $ 0.42   $ 0.42      
Expected term (years)               5 years      
Closing price of common stock               $ 0.54      
Volatility               109.80%      
Risk-free interest rate               0.45%      
Dividend yield               0.00%      
Allocation to preferred stock and warrants before issuance costs               $ 3,000,000      
Allocation to common stock and warrants before issuance costs               $ 3,900,000      
Restricted Stock Units (RSUs)                      
Temporary Equity And Stockholders Equity [Line Items]                      
Granted               2.9      
Cancelled RSU due to non achievement of performance targets               1.0      
2002 Stock Incentive Plan                      
Temporary Equity And Stockholders Equity [Line Items]                      
Common stock authorized for issuance           3,100,000   3,100,000      
Common stock issued pursuant to options exercised               1,000,000      
Options and restricted stock units outstanding           1,100,000   1,100,000      
Options available for future grants           0   0      
2018 Long-Term Incentive Plan                      
Temporary Equity And Stockholders Equity [Line Items]                      
Common stock authorized for issuance           12,200,000   12,200,000      
Options and restricted stock units outstanding           5,300,000   5,300,000      
Options available for future grants           3,800,000   3,800,000      
Maximum                      
Temporary Equity And Stockholders Equity [Line Items]                      
Series E Preferred stock, shares authorized                     1,000,000
Private Placement                      
Temporary Equity And Stockholders Equity [Line Items]                      
Exercise price of warrants       $ 0.515              
Common stock offered       10,800,000              
July 2020 Warrants                      
Temporary Equity And Stockholders Equity [Line Items]                      
Warrant issued 45,000,000 45,000,000                  
Change in fair value of warrants               $ (5,800,000)      
Issuance costs for common stock warrants           $ 1,600,000   1,600,000      
July 2020 Warrants | Rights Offering                      
Temporary Equity And Stockholders Equity [Line Items]                      
Warrant issued 45,000,000 45,000,000                  
Allocated to the warrants based upon fair values $ 15,300,000 $ 15,300,000                  
Exercise price of warrants $ 0.40 $ 0.40                  
Allocation to preferred stock and warrants before issuance costs               $ 15,300,000      
Series F Convertible Preferred Stock and July 2020 Warrants                      
Temporary Equity And Stockholders Equity [Line Items]                      
Deemed dividend on convertible preferred stock           $ 14,700,000          
Series F Convertible Preferred Stock and July 2020 Warrants | Rights Offering                      
Temporary Equity And Stockholders Equity [Line Items]                      
Exercise price of warrants           $ 0.34   $ 0.34      
Expected term (years)               5 years      
Closing price of common stock               $ 0.44      
Volatility               109.80%      
Risk-free interest rate               0.27%      
Dividend yield               0.00%      
Series F Convertible Preferred Stock                      
Temporary Equity And Stockholders Equity [Line Items]                      
Sale of common stock, shares               17,000      
Series F Preferred Stock and July Two Thousand Twenty Amendment | Rights Offering                      
Temporary Equity And Stockholders Equity [Line Items]                      
Exercise price of warrants           $ 0.21   $ 0.21      
Expected term (years)               5 years      
Closing price of common stock               $ 0.28      
Volatility               109.50%      
Risk-free interest rate               0.26%      
Dividend yield               0.00%      
Series F Convertible Preferred Stock                      
Temporary Equity And Stockholders Equity [Line Items]                      
Series F Preferred stock, shares issued 18,000 18,000                  
Common stock value           $ 1,000   $ 1,000      
Conversion price               $ 0.40      
Proceeds from offering, net of underwriting discounts and commissions               $ 18,000,000      
Broker fees and related expenses               1,900,000      
Proceeds of common stock and warrants $ 18,000,000                    
Warrants issued in connection with debt instruments           $ 2,700,000   15,300,000      
Deemed dividend on convertible preferred stock   $ 2,700,000           14,700,000      
Series E Preferred stock, shares authorized                     18,000
Series E Preferred stock, par value                     $ 0.001
Series F Convertible Preferred Stock | Rights Offering                      
Temporary Equity And Stockholders Equity [Line Items]                      
Proceeds allocated to the warrants based upon fair values $ 2,700,000                    
Sale of common stock, shares 18,000                    
Preferred stock par value $ 0.001 $ 0.001                  
Allocation to preferred stock and warrants before issuance costs               $ 2,700,000      
Series E Convertible Preferred Stock                      
Temporary Equity And Stockholders Equity [Line Items]                      
Series E Preferred stock, shares authorized                     69,565
Series E Preferred stock, par value                     $ 0.001
Series E Preferred stock, shares issued           0   0     69,565
Series E Preferred stock, shares outstanding           0   0     69,565
Series E Convertible Preferred Stock | Private Placement                      
Temporary Equity And Stockholders Equity [Line Items]                      
Temporary equity numbers of shares sold                   69,565  
Conversion Of Preferred Stock Into Common Stock           6,956,500   6,956,500      
Temporary equity net proceeds from conversion to common stock           $ 4,000,000   $ 4,000,000