CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net loss	$ (253,116,000)	$ (80,127,000)	$ (109,544,000)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	45,337,000	48,451,000	54,457,000
Provision for doubtful accounts	589,000	918,000	1,857,000
Deferred income taxes	(2,134,000)	(50,535,000)	(56,800,000)
Lower of cost or market inventory adjustment	0	1,515,000	4,546,000
Loss on disposal or impairment of assets	125,778,000	889,000	44,111,000
Loss on sale of Russian proppant business	25,101,000	0	0
Foreign currency transaction gain, net	(35,000)	(119,000)	(94,000)
Stock compensation expense	4,892,000	5,939,000	7,547,000
PIK accrual on notes payable, related parties	2,040,000	0	0
Change in fair value of derivative instruments	(930,000)	(7,687,000)	11,155,000
Changes in operating assets and liabilities:
Trade accounts and other receivables	(20,533,000)	24,569,000	81,371,000
Inventories	10,524,000	6,433,000	27,022,000
Prepaid expenses and other current assets	724,000	1,726,000	1,437,000
Accounts payable	11,666,000	631,000	(7,861,000)
Accrued expenses	8,687,000	(8,405,000)	(9,104,000)
Other, net	2,949,000	1,730,000	697,000
Income tax receivable, net	(357,000)	36,137,000	19,780,000
Net cash (used in) provided by operating activities	(38,818,000)	(17,935,000)	70,577,000
Investing activities
Capital expenditures	(2,152,000)	(6,848,000)	(62,747,000)
Net proceeds from sale of Russian proppant business	21,154,000	0	0
Net cash provided by (used in) investing activities	19,002,000	(6,848,000)	(62,747,000)
Financing activities
Proceeds from long-term debt	12,349,000	0	70,000,000
Repayments on long-term debt	(3,250,000)	(32,099,000)	(7,000,000)
Repayments on insurance financing agreement	(1,296,000)	(917,000)	0
Payment of debt issuance costs	(989,000)	(339,000)	0
Proceeds from notes payable, related parties	0	25,000,000	0
Dividends paid	0	0	(14,666,000)
Purchase of common stock	(539,000)	(450,000)	(580,000)
Net cash provided by financing activities	6,275,000	36,759,000	47,754,000
Effect of exchange rate changes on cash	246,000	838,000	(1,016,000)
Net (decrease) increase in cash and cash equivalents and restricted cash	(13,295,000)	12,814,000	54,568,000
Cash and cash equivalents and restricted cash at beginning of year	91,680,000	78,866,000	24,298,000
Cash and cash equivalents and restricted cash at end of year	78,385,000	91,680,000	78,866,000
Supplemental cash flow information
Interest paid	2,319,000	5,269,000	2,613,000
Income taxes paid	457,000	0	0
ATM Program
Financing activities
Proceeds from issuance of common stock under ATM program	$ 0	$ 45,564,000	$ 0