CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Service revenue	$ 404,234	$ 380,003	$ 347,979
Operating expenses:
Network operations (including $584, $488 and $507 of equity-based compensation expense, respectively), exclusive of amounts shown separately	174,510	159,893	150,225
Selling, general, and administrative (including $10,931, $9,083 and $8,212 of equity-based compensation expense, respectively)	113,103	107,679	87,242
Depreciation and amortization	70,527	69,481	64,358
Total operating expenses	358,140	337,053	301,825
Gains on equipment transactions	5,443	10,950
Gain on Lease termination	11,643
Loss on Debt extinguishment and redemption	(10,144)
Operating income	53,036	53,900	46,154
Interest income and other	956	536	2,630
Interest expense	(41,280)	(49,945)	(41,797)
Income before income taxes	12,712	4,491	6,987
Income tax (expense) benefit	(7,816)	(3,694)	49,702
Net income	4,896	797	56,689
Comprehensive income (loss)
Net income	4,896	797	56,689
Foreign currency translation adjustment	(8,231)	(8,598)	1,469
Comprehensive (loss) income	$ (3,335)	$ (7,801)	$ 58,158
Net income (loss) per common share:
Basic net income per common share	$ 0.11	$ 0.02	$ 1.22
Diluted net income per common share	0.11	0.02	1.21
Dividends declared per common share (in dollars per share)	$ 1.46	$ 1.17	$ 0.76
Weighted-average common shares - basic (in shares)	44,888,723	45,960,720	46,286,735
Weighted-average common shares - diluted (in shares)	45,159,489	46,349,670	46,996,904