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Segment Reporting and Significant Concentration - Summary of Revenues from Significant Clients (Details) - Customer Concentration Risk - Sales Revenue, Net
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Comcast      
Segment Reporting Information [Line Items]      
Revenue by Major Client, Percentage 28.00% 26.00% 24.00%
Charter      
Segment Reporting Information [Line Items]      
Revenue by Major Client, Percentage 22.00% 21.00% 21.00%
DISH      
Segment Reporting Information [Line Items]      
Revenue by Major Client, Percentage 11.00% 13.00% 14.00%