CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Service Revenue
Service revenue	$ 446,900	$ 404,234	$ 380,003
Operating expenses:
Network operations (including $573, $584 and $488 of equity-based compensation expense, respectively), exclusive of amounts shown separately	194,066	174,510	159,893
Selling, general, and administrative (including $10,162, $10,931 and $9,083 of equity-based compensation expense, respectively)	120,709	113,103	107,679
Depreciation and amortization expense	75,235	70,527	69,481
Total operating expenses	390,010	358,140	337,053
Gains on equipment transactions	7,739	5,443	10,950
Gains on capital lease terminations		11,643
Losses on debt extinguishment and redemption	(587)	(10,144)
Operating income	64,042	53,036	53,900
Interest income and other	1,021	956	536
Interest expense	(40,803)	(41,280)	(49,945)
Income before income taxes	24,260	12,712	4,491
Income tax expense	(9,331)	(7,816)	(3,694)
Net income	14,929	4,896	797
Comprehensive income (loss):
Net income	14,929	4,896	797
Foreign currency translation adjustment	(2,500)	(8,231)	(8,598)
Comprehensive income (loss)	$ 12,429	$ (3,335)	$ (7,801)
Net income per common share:
Basic net income per common share	$ 0.33	$ 0.11	$ 0.02
Diluted net income per common share	0.33	0.11	0.02
Dividends declared per common share (in dollars per share)	$ 1.51	$ 1.46	$ 1.17
Weighted-average common shares - basic (in shares)	44,641,805	44,888,723	45,960,720
Weighted-average common shares - diluted (in shares)	44,873,030	45,159,489	46,349,670