Accounts Receivable, Net and Revenue Concentrations - Net Sales to Significant Customers (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue, Major Customer [Line Items]
Net sales	$ 182,717	$ 175,652	$ 509,938	$ 514,638
Net Sales \| Comcast Corporation
Revenue, Major Customer [Line Items]
Net sales	$ 32,336	$ 36,811	$ 99,853	$ 122,009
Percent of net sales	17.70%	21.00%	19.60%	23.70%
Net Sales \| AT&T
Revenue, Major Customer [Line Items]
Net sales	$ 0	$ 20,117	$ 0	$ 61,057
Percent of net sales	0.00%	11.50%	0.00%	11.90%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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