Accounts Receivable, Net and Revenue Concentrations - Net Sales to Significant Customers (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue, Major Customer [Line Items]
Net sales	$ 164,698	$ 161,406
Net Sales | Comcast Corporation
Revenue, Major Customer [Line Items]
Net sales	$ 37,975	$ 42,247
Percent of net sales	23.10%	26.20%
Net Sales | AT&T
Revenue, Major Customer [Line Items]
Net sales	$ 0	$ 19,200
Percent of net sales	0.00%	11.90%