CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating revenue:
Total operating revenue	$ 630,854	$ 611,991	$ 535,288
Operating expenses
Selling, general and administrative	113,222	165,937	133,325
Acquisition, integration and migration expenses	0	11,030	42,232
Depreciation and amortization	166,405	177,007	143,685
Total operating expenses	537,608	565,481	512,762
Operating income (loss)	93,246	46,510	22,526
Other income (expense):
Interest expense	(34,847)	(38,237)	(25,102)
Gain (loss) on investments, net	(275)	564	271
Non-operating income (loss), net	3,988	4,420	4,250
Income (loss) before income taxes	62,112	13,257	1,945
Income tax (benefit) expense	15,517	(53,133)	2,840
Net income (loss)	46,595	66,390	(895)
Other comprehensive income (loss):
Unrealized gain (loss) on interest rate hedge, net of tax	50	1,442	6,373
Comprehensive income (loss)	$ 46,645	$ 67,832	$ 5,478
Net income (loss) per share, basic and diluted:
Basic net income (loss) per share (in dollars per share)	$ 0.94	$ 1.35	$ (0.02)
Diluted net income (loss) per share (in dollars per share)	$ 0.93	$ 1.33	$ (0.02)
Weighted average shares outstanding, basic (in shares)	49,542	49,150	48,807
Weighted average shares outstanding, diluted (in shares)	50,063	50,026	48,807
Cash dividend declared per share (in dollars per share)	$ 0.27	$ 0.26	$ 0.25
Service revenue and other
Operating revenue:
Total operating revenue	$ 562,456	$ 601,673	$ 523,748
Equipment revenue
Operating revenue:
Total operating revenue	68,398	10,318	11,540
Cost of services
Operating expenses
Cost of services and cost of goods sold	194,022	188,721	163,969
Cost of goods sold
Operating expenses
Cost of services and cost of goods sold	$ 63,959	$ 22,786	$ 29,551