Sale of Wireless Operations - Components of Gain on Sale of Assets (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2015
Consideration:
Cash	$ 44,688
Cash held in escrow	228
Total consideration	285,388
Carrying value of assets and liabilities sold:
Assets and liabilities, net	5,349
Net change in deferred capacity revenue	(18,385)
Total carrying value of assets and liabilities sold	237,156
Gain on disposal of assets	48,232
After Purchase Price Adjustments [Member]
Consideration:
Cash		$ 44,688
Total consideration		285,160
Carrying value of assets and liabilities sold:
Assets and liabilities, net		5,121
Net change in deferred capacity revenue		(18,385)
Total carrying value of assets and liabilities sold		236,928
Gain on disposal of assets		48,232
2010 Senior Credit Facility Term Loan Due 2016 [Member]
Consideration:
Principal payment on 2010 Senior Credit Facility	240,472
2010 Senior Credit Facility Term Loan Due 2016 [Member] | After Purchase Price Adjustments [Member]
Consideration:
Principal payment on 2010 Senior Credit Facility		240,472
Alaska Wireless Network, LLC [Member]
Carrying value of assets and liabilities sold:
Equity investment	$ 250,192
Alaska Wireless Network, LLC [Member] | After Purchase Price Adjustments [Member]
Carrying value of assets and liabilities sold:
Equity investment		$ 250,192