Accounts Receivable, Net and Revenue Concentrations - Revenue and Trade Receivables by Significant Customer (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue, Major Customer [Line Items]
Net sales	$ 181,152	$ 175,652	$ 177,580	$ 161,406	$ 160,542	$ 169,185	$ 170,986	$ 150,658	$ 695,790	$ 651,371	$ 602,833
Accounts receivable, net	151,578				124,592				151,578	124,592
Revenue, Net | Comcast Corporation
Revenue, Major Customer [Line Items]
Net sales									$ 159,829	$ 149,476	$ 129,475
Concentration risk percentage									23.00%	22.90%	21.50%
Revenue, Net | AT&T
Revenue, Major Customer [Line Items]
Net sales									$ 77,888	$ 74,704	$ 80,820
Concentration risk percentage									11.20%	11.50%	13.40%
Trade Accounts Receivable | Comcast Corporation
Revenue, Major Customer [Line Items]
Concentration risk percentage									16.60%	19.00%
Accounts receivable, net	25,142				23,716				$ 25,142	$ 23,716
Trade Accounts Receivable | AT&T
Revenue, Major Customer [Line Items]
Concentration risk percentage									0.00%	11.30%
Accounts receivable, net	$ 0				$ 14,108				$ 0	$ 14,108