UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating revenue:
Operating revenues	$ 158,843	$ 154,138
Operating expenses:
Selling, general and administrative	28,722	28,750
Depreciation and amortization	41,179	43,487
Total operating expenses	134,056	137,384
Operating income (loss)	24,787	16,754
Other income (expense):
Interest expense	(7,954)	(9,332)
Gain (loss) on investments, net	250	(32)
Non-operating income (loss), net	1,037	1,021
Income (loss) before income taxes	18,120	8,411
Income tax expense (benefit)	4,210	1,828
Net income (loss)	13,910	6,583
Other comprehensive income (loss):
Unrealized gain (loss) on interest rate hedge, net of tax		3,062
Unrealized gain (loss) on interest rate hedge, net of tax	(2,728)
Comprehensive income (loss)	$ 11,182	$ 9,645
Net income (loss) per share, basic and diluted:
Basic net income (loss) per share (in dollars per share)	$ 0.28	$ 0.13
Diluted net income (loss) per share (in dollars per share)	$ 0.28	$ 0.13
Weighted average shares outstanding, basic (in shares)	49,775	49,474
Weighted average shares outstanding, diluted (in shares)	50,115	50,024
Service revenue and other
Operating revenue:
Operating revenues	$ 143,231	$ 136,559
Equipment revenue
Operating revenue:
Operating revenues	15,612	17,579
Cost of services
Operating expenses:
Cost of services	49,518	49,342
Cost of goods sold
Operating expenses:
Cost of services	$ 14,637	$ 15,805