Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Summary of Financial Instruments Measured on a Recurring Basis (Details)

v3.19.2
Fair Value Measurements - Summary of Financial Instruments Measured on a Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets $ 19,478 $ 11,767
Fair value of financial liabilities 12,319 986
Warrant liabilities    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial liabilities 5,459 986
Derivative liability    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial liabilities 6,860  
Cash    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets   213
Restricted cash    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets 328 328
Money market funds    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets 19,150 11,226
Quoted Prices in Active Markets for Identical Assets (Level 1)    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets 19,478 11,767
Fair value of financial liabilities 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Warrant liabilities    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial liabilities 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Derivative liability    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial liabilities 0  
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets   213
Quoted Prices in Active Markets for Identical Assets (Level 1) | Restricted cash    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets 328 328
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets 19,150 11,226
Significant Other Observable Inputs (Level 2)    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets 0 0
Fair value of financial liabilities 0 0
Significant Other Observable Inputs (Level 2) | Warrant liabilities    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial liabilities 0 0
Significant Other Observable Inputs (Level 2) | Derivative liability    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial liabilities 0  
Significant Other Observable Inputs (Level 2) | Cash    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets   0
Significant Other Observable Inputs (Level 2) | Restricted cash    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets 0 0
Significant Other Observable Inputs (Level 2) | Money market funds    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets 0 0
Significant Unobservable Inputs (Level 3)    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets 0 0
Fair value of financial liabilities 12,319 986
Significant Unobservable Inputs (Level 3) | Warrant liabilities    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial liabilities 5,459 986
Significant Unobservable Inputs (Level 3) | Derivative liability    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial liabilities 6,860  
Significant Unobservable Inputs (Level 3) | Cash    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets   0
Significant Unobservable Inputs (Level 3) | Restricted cash    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets 0 0
Significant Unobservable Inputs (Level 3) | Money market funds    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Fair value of financial assets $ 0 $ 0