Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Additional Information (Details)

v3.19.2
Summary of Significant Accounting Policies - Additional Information (Details)
$ in Thousands
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2019
USD ($)
Customer
Jun. 30, 2018
Customer
Jun. 30, 2019
USD ($)
Customer
Jun. 30, 2018
Customer
Dec. 31, 2018
Customer
Jan. 01, 2019
USD ($)
Accounting Policies [Line Items]            
Operating lease right-of-use asset | $ $ 697   $ 697     $ 900
Operating lease liability | $ $ 753   $ 753     $ 900
Customer Concentration Risk | Accounts Receivable            
Accounting Policies [Line Items]            
Number of customers | Customer     1   1  
Customer Concentration Risk | Revenues            
Accounting Policies [Line Items]            
Number of customers | Customer 2 2 2 2    
Customer One | Customer Concentration Risk | Accounts Receivable            
Accounting Policies [Line Items]            
Concentration risk percentage     24.00%   77.00%  
Customer One | Customer Concentration Risk | Revenues            
Accounting Policies [Line Items]            
Concentration risk percentage 20.00% 24.00% 21.00% 22.00%    
Customer Two | Customer Concentration Risk | Revenues            
Accounting Policies [Line Items]            
Concentration risk percentage 14.00% 14.00% 14.00% 16.00%