CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenues	$ 57,989	$ 43,572	$ 107,356	$ 78,242
Cost of sales (exclusive of depreciation and amortization shown below)	50,818	46,138	101,788	89,025
Depreciation and amortization	8,323	10,867	16,735	22,108
Gross loss	(1,152)	(13,433)	(11,167)	(32,891)
Selling, general and administrative expenses (exclusive of depreciation and amortization shown below)	10,685	9,623	20,292	19,779
Depreciation and amortization	620	642	1,234	1,283
Loss on sale of Russian proppant business	350	0	350	0
Gain on disposal or impairment of assets	(55)	0	(59)	0
Operating loss	(12,752)	(23,698)	(32,984)	(53,953)
Other expense:
Interest expense, net	(2,084)	(1,627)	(4,101)	(3,715)
Other, net	31	4	8	191
Nonoperating income (expense), total	(2,053)	(1,623)	(4,093)	(3,524)
Loss before income taxes	(14,805)	(25,321)	(37,077)	(57,477)
Income tax expense (benefit)	7	(499)	7	(211)
Net loss	$ (14,812)	$ (24,822)	$ (37,084)	$ (57,266)
Loss per share:
Basic	$ (0.55)	$ (0.93)	$ (1.38)	$ (2.15)
Diluted	(0.55)	(0.93)	(1.38)	(2.15)
Other information:
Dividends declared per common share	$ 0	$ 0	$ 0	$ 0