Restatement of Previously Issued Financial Statements - Condensed Consolidated Statement of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Depreciation, depletion and amortization	$ 20,737	$ 13,498	$ 36,162	$ 25,472
Total expenses	35,290	51,662	62,442	70,442
Income (loss) from operations	12,562	(33,527)	22,102	(34,691)
Loss before income taxes	(24,696)	(36,316)	(44,341)	(31,496)
Income tax benefit	3,103	12,601	6,211	10,898
Net loss attributable to common stockholders	$ (23,525)	$ (24,011)	$ (41,951)	$ (20,894)
Net loss per common share
Basic (in dollars per share)	$ (0.96)	$ (1.10)	$ (1.71)	$ (0.96)
Diluted (in dollars per share)	$ (0.96)	$ (1.10)	$ (1.71)	$ (0.96)
As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Depreciation, depletion and amortization	$ 19,464	$ 12,551	$ 35,027	$ 24,693
Total expenses	34,017	50,715	61,307	69,663
Income (loss) from operations	13,835	(32,580)	23,237	(33,912)
Loss before income taxes	(23,423)	(35,369)	(43,206)	(30,717)
Income tax benefit	4,648	12,208	7,778	10,621
Net loss attributable to common stockholders	$ (20,707)	$ (23,457)	$ (39,249)	$ (20,392)
Net loss per common share
Basic (in dollars per share)	$ (0.84)	$ (1.07)	$ (1.60)	$ (0.93)
Diluted (in dollars per share)	$ (0.84)	$ (1.07)	$ (1.60)	$ (0.93)
Correction
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Depreciation, depletion and amortization	$ 1,273	$ 947	$ 1,135	$ 779
Total expenses	1,273	947	1,135	779
Income (loss) from operations	(1,273)	(947)	(1,135)	(779)
Loss before income taxes	(1,273)	(947)	(1,135)	(779)
Income tax benefit	(1,545)	393	(1,567)	277
Net loss attributable to common stockholders	$ (2,818)	$ (554)	$ (2,702)	$ (502)
Net loss per common share
Basic (in dollars per share)	$ 0	$ 0	$ 0	$ 0
Diluted (in dollars per share)	$ 0	$ 0	$ 0	$ 0