BASIS OF PRESENTATION - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Prior period corrections
Purchases of spectrum licenses and other intangible assets, including deposits		$ 10,860
Payment for purchase of securities		2,000
Keytech
Prior period corrections
Other asset acquired		3,200
Innovative
Prior period corrections
Other asset acquired		$ 4,300
Termination and Access Fees [Member]
Prior period corrections
Reclassification, decrease (increase) to expense	$ 1,100		$ 3,100
Engineering and Operations Expenses [Member]
Prior period corrections
Reclassification, decrease (increase) to expense	600		2,400
Equipment Expense [Member]
Prior period corrections
Reclassification, decrease (increase) to expense	100		200
Selling and Marketing Expense [Member]
Prior period corrections
Reclassification, decrease (increase) to expense	(600)		(1,300)
General and administrative expense
Prior period corrections
Reclassification, decrease (increase) to expense	$ (300)		$ (800)