Equity Method Investments - Summarized Financial Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 02, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule of Equity Method Investments [Line Items]
Operating revenues		$ 56,483	$ 54,735	$ 169,073	$ 176,186
Operating income		4,100	8,178	12,781	43,116
Net income		$ 354	$ 1,239	$ 757	$ 12,615
Alaska Wireless Network, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Operating revenues	$ 21,457
Gross profit	15,745
Operating income	9,757
Net income	9,722
Adjusted Free Cash Flow	$ 10,805