Condended Financial Information of Registrant Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 118,333	$ 47,772	$ 167,788	$ 89,210
Restricted cash	744	1,246
Prepaid and other current assets	17,279	53,380
Total current assets	603,544	403,108
Property and equipment
Total property and equipment	529,638	500,989
Less accumulated depreciation and depletion	(79,622)	(49,727)
Property, plant and equipment, net	450,016	451,262
Long-term assets
Other long-term assets	32,864	46,596
Total assets	1,347,407	1,145,433	892,261
Current liabilities
Accounts payable	52,543	65,190
Other accrued liabilities	27,444	35,186
Total current liabilities	470,952	382,765
Long-term liabilities
Long-term debt, net of current maturities	384,812	350,110
Common stock warrants	6,808	5,134
Long-term capital lease obligations	1,220	1,780
Total liabilities	899,688	776,524
Stockholders’ equity
Preferred stock, $0.01 par value: 3,000,000 shares authorized, none issued	0	0
Common stock, $0.01 par value; 500,000,000 shares authorized at December 31, 2017 and December 31, 2016, 45,776,087 shares and 45,533,913 shares issued at December 31, 2017 and December 31, 2016, respectively	458	455
Additional paid-in capital	593,295	587,057
Accumulated deficit	(148,178)	(220,799)
Accumulated other comprehensive income	2,144	2,196
Total stockholders’ equity	447,719	368,909
Total liabilities and stockholders’ equity	1,347,407	1,145,433
Parent Company
Current assets
Cash and cash equivalents	65,615	10,361	$ 91,023	$ 70,114
Restricted cash	744	746
Prepaid and other current assets	11,768	9,200
Due from subsidiaries	8,113	66,900
Total current assets	86,240	87,207
Property and equipment
Total property and equipment	15,773	10,259
Less accumulated depreciation and depletion	(6,226)	(3,485)
Property, plant and equipment, net	9,547	6,774
Long-term assets
Investment in subsidiaries	552,748	513,693
Other long-term assets	1,976	1,976
Total assets	650,511	609,650
Current liabilities
Accounts payable	4,510	4,529
Other accrued liabilities	12,913	8,141
Due to subsidiaries	82,524	73,529
Total current liabilities	99,947	86,199
Long-term liabilities
Long-term debt, net of current maturities	95,486	148,456
Common stock warrants	6,808	5,134
Long-term capital lease obligations	551	952
Total liabilities	202,792	240,741
Stockholders’ equity
Preferred stock, $0.01 par value: 3,000,000 shares authorized, none issued	0	0
Common stock, $0.01 par value; 500,000,000 shares authorized at December 31, 2017 and December 31, 2016, 45,776,087 shares and 45,533,913 shares issued at December 31, 2017 and December 31, 2016, respectively	458	455
Additional paid-in capital	593,295	587,057
Accumulated deficit	(148,178)	(220,799)
Accumulated other comprehensive income	2,144	2,196
Total stockholders’ equity	447,719	368,909
Total liabilities and stockholders’ equity	$ 650,511	$ 609,650

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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- Definition

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).