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Investment Unit - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended
Mar. 12, 2014
Dec. 31, 2013
Mar. 31, 2019
Dec. 31, 2018
Investment Unit Details [Line Items]        
Debt instrument, face amount     $ 4,500,000  
Debt instrument, interest rate, stated percentage     8.00%  
Debt instrument, maturity date     Aug. 13, 2020  
Debt instrument, description     If no event of default occurs prior to August 13, 2020, the Promissory Note and all related interest will be cancelled.  
Warrant, right to purchase, percentage     80.00%  
Warrant, discount rate     20.00%  
Class of warrant or right, exercise price of warrants or rights $ 0.001   $ 0.001  
Conversion of warrants to common stock 1,235,219      
Fair value adjustment of warrants   $ 2,500,000 $ 0  
Value of investment unit     $ 0 $ 0
Series B Preferred Stock        
Investment Unit Details [Line Items]        
Stock issued during period, shares, new issues 184,797