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Summary of Significant Accounting Policies - Concentration of Credit Risk (Details)
$ in Millions
12 Months Ended
Dec. 31, 2016
USD ($)
customer
financial_instituion
Dec. 31, 2015
USD ($)
Dec. 31, 2014
customer
Customer Concentration Risk | Revenue | One Major Customer      
Concentration Risk [Line Items]      
Concentration risk number of customers that accounted for greater than specified benchmark 1   1
Concentration risk, percentage 11.50% 10.00% 12.00%
Customer Concentration Risk | Accounts Receivable      
Concentration Risk [Line Items]      
Concentration risk number of customers that accounted for greater than specified benchmark 0   0
Concentration risk, percentage 10.00%    
Customer Concentration Risk | Accounts Receivable | One Major Customer      
Concentration Risk [Line Items]      
Concentration risk, percentage     10.00%
United States      
Concentration Risk [Line Items]      
Number of financial institutions holding cash in excess of federally insured limits | financial_instituion 1    
Foreign Countries      
Concentration Risk [Line Items]      
Cash that is not federally insured | $ $ 2.1 $ 1.9