Summary of Sales to Customers (Detail) - Customer Concentration Risk - Sales - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Charter and affiliates
Revenue, Major Customer [Line Items]
Customers and affiliates	$ 985,237	$ 1,064,408	[1]	$ 960,497
Percentage of sales	14.90%	15.60%		20.00%
Comcast and affiliates
Revenue, Major Customer [Line Items]
Customers and affiliates	$ 1,479,415	$ 1,637,519	[1]	$ 1,007,376
Percentage of sales	22.40%	24.00%		21.00%

[1] Revenues were reduced $30.2 million in 2016, as a result of warrants held by Charter and Comcast that are intended to incent additional purchases from them. (see Note 17 Warrants for additional information).