Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Statement of Cash Flows [Abstract]
Net loss	$ (41,744)	$ (41,858)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	28,558	41,073
Bad debt expense	261	427
Accretion of asset retirement obligations	82	80
Amortization of deferred financing costs	241	238
Income on disposal of assets, net	(1,459)	(5,467)
Share-based compensation	2,230	2,902
Changes in working capital:
Accounts receivable	2,422	(24,447)
Other current assets	(1,741)	5,850
Accounts payable, accrued interest and accrued expenses	(4,647)	(565)
Share-based compensation liability awards	34	799
Other assets and liabilities	4,400	5,710
Net cash used in operating activities	(11,363)	(15,258)
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(12,362)	(17,173)
Proceeds from sale of assets	4,780	8,875
Net cash used in investing activities	(7,582)	(8,298)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repayments of long-term debt	(1,250)	(1,250)
Payment of deferred financing costs	828	0
Repurchases of common stock	4	0
Proceeds from exercise of warrants	0	3
Net cash used in financing activities	(2,082)	(1,247)
Net decrease in cash, cash equivalents and restricted cash	(21,027)	(24,803)
Cash, cash equivalents, and restricted cash, beginning of period	50,311	77,065
Cash, cash equivalents, and restricted cash, end of period	$ 29,284	$ 52,262