Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation and Summary of Significant Accounting Policies - Fair Value, Level 3 Rollforward (Details)

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Basis of Presentation and Summary of Significant Accounting Policies - Fair Value, Level 3 Rollforward (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Liability Warrants    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Change in value $ 100 $ 400
Significant other unobservable inputs (Level 3) | Liability Warrants    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 20  
Change in value (20)  
Ending balance 0  
Significant other unobservable inputs (Level 3) | Contingently Issuable Shares    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 1,448  
Change in value (544)  
Ending balance 904  
Significant other unobservable inputs (Level 3) | Earn-out liability    
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]    
Beginning balance 114  
Change in value 0  
Ending balance $ 114