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Major Customers and Accounts Receivable - Additional Information (Details) - Customer Concentration Risk
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
One Major Customer | Sales Revenue, Net    
Concentration Risk [Line Items]    
Concentration risk percentage 23.00% 19.00%
One Major Customer | Accounts Receivable    
Concentration Risk [Line Items]    
Concentration risk percentage 18.00% 10.00%
Two Customers | Accounts Receivable    
Concentration Risk [Line Items]    
Concentration risk percentage 29.00%