Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenues	$ 28,439	$ 23,445	$ 79,820	$ 64,966
Costs and expenses
Operating costs	18,420	18,247	55,312	48,953
Selling, general and administrative	3,903	2,948	10,877	10,101
Merger expenses	1,933	0	2,376	0
Depreciation and amortization	6,831	6,529	20,001	19,120
Asset impairment, net	431	899	396	1,574
(Gain) loss on disposition of assets, net	(260)	0	(675)	1,573
Total costs and expenses	31,258	28,623	88,287	81,321
Operating loss	(2,819)	(5,178)	(8,467)	(16,355)
Interest expense	(1,168)	(772)	(3,049)	(2,088)
Loss before income taxes	(3,987)	(5,950)	(11,516)	(18,443)
Income tax (benefit) expense	(50)	30	(120)	110
Net loss	$ (3,937)	$ (5,980)	$ (11,396)	$ (18,553)
Loss per share:
Basic and diluted (in dollars per share)	$ (0.10)	$ (0.16)	$ (0.30)	$ (0.49)
Weighted average number of common shares outstanding:
Basic and diluted (in shares)	38,253	37,839	38,210	37,688