Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Concentration of Credit Risk and Significant Customers (Details)

v3.19.1
Summary of Significant Accounting Policies - Concentration of Credit Risk and Significant Customers (Details) - Customer Concentration Risk
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Customer A | REVENUES      
Concentration Risk [Line Items]      
Concentration risk, percentage 60.00% 29.00% 0.00%
Customer A | ACCOUNTS RECEIVABLE      
Concentration Risk [Line Items]      
Concentration risk, percentage 65.00% 56.00%  
Customer B | REVENUES      
Concentration Risk [Line Items]      
Concentration risk, percentage 8.00% 30.00% 57.00%
Customer B | ACCOUNTS RECEIVABLE      
Concentration Risk [Line Items]      
Concentration risk, percentage 3.00% 12.00%  
Customer C | REVENUES      
Concentration Risk [Line Items]      
Concentration risk, percentage 0.00% 1.00% 11.00%
Customer C | ACCOUNTS RECEIVABLE      
Concentration Risk [Line Items]      
Concentration risk, percentage 0.00% 0.00%