Restatement of Previously Issued Financial Statements - Condensed Consolidated Statements of Cash Flows and Operating Activities (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss	$ (19,710,000)	$ (7,124,000)	$ (57,840,000)	$ (27,722,000)
Depreciation, depletion and amortization			59,937,000	42,003,000
Deferred taxes			$ (7,145,000)	(16,116,000)
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss		(6,761,000)		(26,857,000)
Depreciation, depletion and amortization				40,623,000
Deferred taxes				(15,601,000)
Correction
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss		$ (363,000)		(865,000)
Depreciation, depletion and amortization				1,380,000
Deferred taxes				$ (515,000)