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 ($)
 3 Months Ended 9 Months Ended 12 Months Ended
Jun. 11, 2021
Feb. 10, 2021
Feb. 10, 2021
Jul. 23, 2020
Sep. 30, 2021
Mar. 31, 2021
Dec. 31, 2020
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2020
Temporary Equity And Stockholders Equity [Line Items]                      
Temporary equity preferred stock, shares authorized         1,000,000       1,000,000    
Common stock, shares authorized         180,000,000   180,000,000   180,000,000   180,000,000
Common stock, shares issued   14,000,000 14,000,000   153,322,000   97,709,000   153,322,000   97,709,000
Shares Issued, Price Per Share   $ 1.03 $ 1.03                
Equity raise of gross proceeds     $ 14,400,000                
Series F Preferred stock, shares issued         0   1,000   0   1,000
Common stock value       $ 1,000 $ 153,000   $ 98,000   $ 153,000   $ 98,000
Proceeds from Warrant Exercise           $ 15,000,000.0          
Proceeds from the exercise of common stock warrants             $ 1,500,000   $ 16,560,000 $ 46,000  
Expected term (years)         6 years 1 month 6 days       6 years 1 month 6 days 5 years 6 months  
Risk-free interest rate         0.98%     0.00% 0.86% 0.37%  
Change in fair value of warrants                 $ 0 $ (5,850,000)  
Issuance costs for common stock warrants                 $ 0 1,640,000  
Series E Preferred stock, shares authorized         1,000,000       1,000,000    
Conversion of preferred stock into common stock         251       251    
Convertible preferred stock, shares outstanding         0   0   0   0
Compensation expense related to stock options         $ 200,000     $ 800,000 $ 1,500,000 2,400,000  
Total unrecognized compensation expense         800,000     1,400,000 $ 800,000 1,400,000  
Unrecognized share based compensation expense to be recognized over weighted-average period                 1 year 6 months    
Allocated Share-based Compensation Expense         $ 192,000     $ 847,000 $ 1,488,000 $ 2,367,000  
Outstanding stock options, RSUs and warrants excluded from diluted loss per share                 24,000,000.0 67,200,000  
July 2020 Warrants                      
Temporary Equity And Stockholders Equity [Line Items]                      
Warrant issued       45,000,000              
Proceeds from issuance of warrants                 $ 15,300,000    
Warrants issued in connection with debt instruments                 $ 15,300,000    
July 2020 Warrants | Rights Offering                      
Temporary Equity And Stockholders Equity [Line Items]                      
Allocated to the warrants based upon fair values       $ 15,300,000              
Common Stock                      
Temporary Equity And Stockholders Equity [Line Items]                      
Other offering expenses   $ 1,100,000                  
Series F Convertible Preferred Stock                      
Temporary Equity And Stockholders Equity [Line Items]                      
Conversion price       $ 0.40              
Series E Convertible Preferred Stock                      
Temporary Equity And Stockholders Equity [Line Items]                      
Temporary equity preferred stock, shares authorized         69,565       69,565    
Series E Preferred stock, shares authorized         69,565       69,565    
Convertible preferred stock, shares issued         0   0   0   0
Preferred stock par value         $ 0.001       $ 0.001    
Series F Convertible Preferred Stock                      
Temporary Equity And Stockholders Equity [Line Items]                      
Temporary equity preferred stock, shares authorized         18,000       18,000    
Convertible preferred stock, Common shares issued upon conversion       2,500              
Series F Preferred stock, shares issued       18,000              
Proceeds from issuance of warrants           2,700,000          
Conversion price       $ 0.40              
Proceeds of common stock and warrants       $ 18,000,000.0              
Warrants issued in connection with debt instruments           $ 2,700,000          
Sale of common stock, shares                 18,000   17,000
Deemed dividend on convertible preferred stock       2,700,000         $ 500,000   $ 14,700,000
Series E Preferred stock, shares authorized         18,000       18,000    
Preferred stock, par value         $ 0.001       $ 0.001    
Convertible preferred stock, shares outstanding         251   882   251   882
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              
Private Placement | Series F Convertible Preferred Stock                      
Temporary Equity And Stockholders Equity [Line Items]                      
Common stock, shares issued         627,500       627,500    
Maximum                      
Temporary Equity And Stockholders Equity [Line Items]                      
Temporary equity preferred stock, shares authorized         1,000,000       1,000,000    
Series E Preferred stock, shares authorized         1,000,000       1,000,000    
2002 Stock Incentive Plan                      
Temporary Equity And Stockholders Equity [Line Items]                      
Common stock authorized for issuance         3,110,000       3,110,000    
Options and restricted stock units outstanding         879,000       879,000    
2018 Long-Term Incentive Plan                      
Temporary Equity And Stockholders Equity [Line Items]                      
Common Stock Issued Pursuant To Options Exercised                 4,744,000    
Increase in Number of Units Available for Issuance 24,700,000                    
Common stock issued pursuant to options exercised                 4,744,000    
2018 Long-Term Incentive Plan | Common Stock                      
Temporary Equity And Stockholders Equity [Line Items]                      
Common stock authorized for issuance         36,921,000       36,921,000    
Options available for future grants         2,400,000       2,400,000    
Restricted Stock Units (RSUs)                      
Temporary Equity And Stockholders Equity [Line Items]                      
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted                 2,800,000    
Cancelled RSU due to non achievement of performance targets                 100,000    
Performance-Based Awards                      
Temporary Equity And Stockholders Equity [Line Items]                      
Compensation expense related to stock options                 $ 0.0   $ 900,000
Phantom Share Units (PSUs)                      
Temporary Equity And Stockholders Equity [Line Items]                      
Allocated Share-based Compensation Expense         $ 200,000       $ 200,000    
Shares issued in period                 10,100,000    
Stock Appreciation Rights (SARs)                      
Temporary Equity And Stockholders Equity [Line Items]                      
Allocated Share-based Compensation Expense         $ 100,000       $ 200,000    
Shares issued in period                 700,000