Accounts Receivable, Net and Revenue Concentrations - Trade Receivables Associated with Significant Customers (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Revenue, Major Customer [Line Items]
Accounts receivable, net	$ 160,055	$ 151,578
Accounts Receivable, Net | Comcast Corporation
Revenue, Major Customer [Line Items]
Accounts receivable, net	$ 27,372	$ 25,142
Percent of accounts receivable, net	17.10%	16.60%