CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Service revenue
Service revenue	$ 128,706	$ 117,203
Operating expenses:
Network operations (including $189 and $111 of equity-based compensation expense, respectively, exclusive of depreciation and amortization shown separately below)	54,875	50,662
Selling, general, and administrative (including $3,595 and $2,536 of equity-based compensation expense, respectively)	33,523	31,461
Depreciation and amortization	19,788	18,538
Total operating expenses	108,186	100,661
Gains on equipment transactions	117	2,124
Operating income	20,637	18,666
Interest income and other, net	1,694	854
Interest expense	(12,408)	(11,891)
Income before income taxes	9,923	7,629
Income tax provision	(3,139)	(3,493)
Net income	6,784	4,136
Comprehensive income:
Net income	6,784	4,136
Foreign currency translation adjustment	2,611	1,328
Comprehensive income	$ 9,395	$ 5,464
Net income per common share:
Basic and diluted net income per common share (in dollars per share)	$ 0.15	$ 0.09
Dividends declared per common share (in dollars per share)	$ 0.50	$ 0.42
Weighted-average common shares - basic (in shares)	44,923,973	44,649,645
Weighted-average common shares - diluted (in shares)	45,294,697	44,917,014