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Summary of Significant Accounting Policies - Concentrations of Credit and Other Risks (Details)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Concentration Risk [Line Items]      
Concentration risk percentage     95.00%
Customer Concentration Risk | Revenue      
Concentration Risk [Line Items]      
Concentration risk percentage 14.00% 13.00% 11.00%
Customer Concentration Risk | One customer | Accounts Receivable      
Concentration Risk [Line Items]      
Concentration risk percentage 10.00%    
Customer Concentration Risk | Two Customers | Accounts Receivable      
Concentration Risk [Line Items]      
Concentration risk percentage   10.00%