CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Service revenue	$ 134,789	$ 129,296	$ 268,930	$ 258,002
Operating expenses:
Network operations	54,407	54,379	108,557	109,252
Selling, general, and administrative	38,566	33,704	74,427	67,227
Depreciation and amortization	19,979	20,216	40,240	40,004
Total operating expenses	112,952	108,299	223,224	216,483
Gains on equipment transactions	185	357	721	475
Operating income	22,022	21,354	46,427	41,994
Interest income and other, net	1,753	189	3,572	1,879
Interest expense	(13,595)	(12,373)	(27,051)	(24,780)
Income before income taxes	10,180	9,170	22,948	19,093
Income tax provision	(3,044)	(2,618)	(6,595)	(5,757)
Net income	7,136	6,552	16,353	13,336
Comprehensive income:
Net income	7,136	6,552	16,353	13,336
Foreign currency translation adjustment	1,786	(6,198)	(39)	(3,587)
Comprehensive income	$ 8,922	$ 354	$ 16,314	$ 9,749
Net income per common share:
Basic net income per common share (in dollars per share)	$ 0.16	$ 0.15	$ 0.36	$ 0.30
Diluted net income per common share (in dollars per share)	0.16	0.14	0.36	0.29
Dividends declared per common share (in dollars per share)	$ 0.60	$ 0.52	$ 1.18	$ 1.02
Weighted-average common shares - basic (in shares)	45,354,327	45,016,767	45,349,397	45,011,616
Weighted-average common shares - diluted (in shares)	45,912,291	45,536,473	45,838,918	45,456,831