Notes Payable - Schedule of Notes Payable (Detail) - USD ($)
Dec. 31, 2019
Oct. 31, 2019
Sep. 30, 2019
May 31, 2019
Dec. 31, 2018
Nov. 30, 2018
Oct. 31, 2018
Jan. 31, 2018
Debt Instrument [Line Items]                
Total face amount $ 16,359,000       $ 9,117,000      
Unamortized discount (3,047,000)       (1,780,000)     $ (271,000)
Total carrying value 13,312,000       7,337,000      
Amount classified as current 13,227,000       4,464,000      
Amount classified as long-term 85,000       2,873,000      
8% Secured Promissory Notes Due February 2019 [Member]                
Debt Instrument [Line Items]                
Total face amount         250,000      
0% Convertible Notes Due January 2021 [Member]                
Debt Instrument [Line Items]                
Total face amount 91,000       275,000      
4% Promissory Note Due December 2020 [Member]                
Debt Instrument [Line Items]                
Total face amount 500,000       847,000      
0% Promissory Note Due April 2019 [Member]                
Debt Instrument [Line Items]                
Total face amount         418,000      
8% Promissory Note Due March 2021 [Member]                
Debt Instrument [Line Items]                
Total face amount         2,107,000      
12% Convertible Notes Due October 2019 [Member]                
Debt Instrument [Line Items]                
Total face amount 1,775,000 $ 1,775,000,000     4,000,000      
Unamortized discount             $ (1,942,000)  
12% Convertible Notes Due November 2019 [Member]                
Debt Instrument [Line Items]                
Total face amount 400,000 400,000,000     $ 1,220,000      
Unamortized discount           $ (118,000)    
12% Convertible Notes Due May 2020 [Member]                
Debt Instrument [Line Items]                
Total face amount 1,500,000              
Unamortized discount       $ (940,000)        
12% Convertible Notes Due July, August and September 2020 [Member]                
Debt Instrument [Line Items]                
Total face amount 4,235,000 $ 4,235,000,000            
Unamortized discount (4,368,000)   $ (4,368,000)          
12% Secured Promissory Note Due September 2020 [Member]                
Debt Instrument [Line Items]                
Total face amount $ 7,858,000