Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 44,723	$ 15,821
Receivables, net	30,374	33,377
Material and supplies	6,950	8,090
Prepaid expenses	4,906	4,093
Other current assets	2,582	7,229
Total current assets	89,535	68,610
Property, plant and equipment, net	608,098	595,997
Intangible assets, net	31,452	32,728
Goodwill	12,104	12,104
Deferred income taxes, net		92,171
Other assets	2,176	2,311
Total assets	743,365	803,921
Current liabilities
Current portion of long-term debt	10,250	3,000
Accounts payable	52,899	53,506
Accrued expenses	13,326	15,293
Advance billings and customer deposits	15,165	15,013
Other current liabilities	6,407	6,327
Total current liabilities	98,047	93,139
Long-term debt	301,351	281,699
Employee benefit obligations	81,678	105,930
Other liabilities	39,039	18,239
Total liabilities	520,115	499,007
Commitments and contingencies (Note 11)
Stockholders' equity
Common stock, par value of $0.01 per share, 245,000,000 shares authorized and 11,587,963 and 11,513,279 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively	116	115
Additional paid-in capital	181,912	179,958
Accumulated other comprehensive loss	(21,239)	(35,218)
Retained earnings	62,461	160,059
Total stockholders' equity	223,250	304,914
Total liabilities and stockholders' equity	$ 743,365	$ 803,921