Quarterly report pursuant to Section 13 or 15(d)

Stock Warrants - Additional Information (Details)

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Stock Warrants - Additional Information (Details) - USD ($)
1 Months Ended 3 Months Ended 6 Months Ended 12 Months Ended
Oct. 15, 2018
Oct. 10, 2018
Oct. 10, 2014
Nov. 18, 2016
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Oct. 31, 2018
Dec. 26, 2017
Equity, Class of Treasury Stock [Line Items]                      
Proceeds from Issuance or Sale of Equity $ 18,600,000                    
Warrants Not Settleable in Cash, Fair Value Disclosure                     $ 9,000
Proceeds from Issuance of Common Stock                 $ 12,200,000    
Class of Warrant or Right, Number of Securities Called by Warrants or Rights 13,672,173                    
Fair Value Adjustment of Warrants         $ 0 $ (783,000) $ 0 $ (3,438,000) $ (4,083,000)    
Conversion of Stock, Shares Converted             7,900        
Class of Warrant or Right, Exercise Price of Warrants or Rights $ 1.38                 $ 1.38  
Class A [Member]                      
Equity, Class of Treasury Stock [Line Items]                      
Stock Issued During Period, Shares, New Issues 2,520,000                    
Class B [Member]                      
Equity, Class of Treasury Stock [Line Items]                      
Stock Issued During Period, Shares, New Issues 15,723                    
Preferred Stock Conversion Price Per Share $ 1.15                    
Series B Preferred Stock [Member]                      
Equity, Class of Treasury Stock [Line Items]                      
Class of Warrant or Right, Number of Securities Called by Warrants or Rights 13,672,173                    
Stock Issued During Period, Value, Issued for Services $ 1,000                    
Preferred Stock, Par or Stated Value Per Share $ 1,000       $ 1,000   $ 1,000   $ 1,000    
Conversion of Stock, Shares Converted 13,672,173                    
IPO [Member]                      
Equity, Class of Treasury Stock [Line Items]                      
Warrants Not Settleable in Cash, Fair Value Disclosure       $ 15,700,000 $ 100,000 624,000 $ 100,000 624,000      
Stock Issued During Period, Shares, New Issues       714,286              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights       1,428,571              
Fair Value Adjustment of Warrants           714,000   3,000,000      
Sale of Stock, Price Per Share     $ 1.47 $ 35.00              
IPO [Member] | Series A [Member]                      
Equity, Class of Treasury Stock [Line Items]                      
Class of Warrant or Right, Exercise Price of Warrants or Rights       50.05              
IPO [Member] | Series B [Member]                      
Equity, Class of Treasury Stock [Line Items]                      
Class of Warrant or Right, Exercise Price of Warrants or Rights       $ 60.20              
Underwritten Public Offering [Member] | October 2018 Warrants [Member]                      
Equity, Class of Treasury Stock [Line Items]                      
Warrant Term 5 years                    
Over-Allotment Option [Member]                      
Equity, Class of Treasury Stock [Line Items]                      
Issuance Of Warrants To Purchase Of Common Stock 1,807,826                    
Stock Issued During Period, Shares, New Issues 2,428,825 2,428,825                  
Class of Warrant or Right, Number of Securities Called by Warrants or Rights 2,428,825 2,428,825                  
Series A Warrants [Member]                      
Equity, Class of Treasury Stock [Line Items]                      
Proceeds from Issuance of Common Stock     $ 19,100,000                
Sale of Stock, Number of Shares Issued in Transaction     14,059,616                
Issuance Of Warrants To Purchase Of Common Stock     0.50                
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number     61.25                
Share Based Compensation Arrangement By Share Based Payment Award Warrants Vested and Expected To Vest Outstanding Number     200,852                
Fair Value of Warrant Liability         $ 0 21,000 $ 0 21,000      
Fair Value Adjustment of Warrants     $ 7,400,000     $ 69,000   $ 395,000      
Warrant [Member]                      
Equity, Class of Treasury Stock [Line Items]                      
Share Based Compensation Arrangement By Share Based Payment Award Non Option Equity Instruments Warrants Exercisable Number                     714
Class of Warrant or Right, Number of Securities Called by Warrants or Rights 13,672,173