CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 80,536	$ 83,708
Accounts receivable	49,042	49,311
Due from related parties	478	0
Inventories, net	70,022	68,683
Derivative financial instruments	0	752
Income tax receivable	1,516	1,601
Other prepaid and deferred charges	33,438	20,361
Other assets	802	741
Total current assets	235,834	225,157
Noncurrent assets
Property, plant and equipment, net	1,408,080	1,432,361
Goodwill	2,280	2,280
Deferred income taxes	0	0
Other assets	43,732	54,978
Total assets	1,689,926	1,714,776
Current liabilities
Accounts payable	32,925	27,678
Royalties and production taxes	57,335	63,018
Accrued expenses	31,375	35,857
Due to related parties	0	71
Other liabilities	2,552	2,567
Total current liabilities	124,187	129,191
Noncurrent liabilities
Senior notes	409,368	475,009
Asset retirement obligations, net of current portion	107,891	97,048
Accumulated postretirement medical benefit obligation, net of current portion	23,701	22,950
Royalties and production taxes	20,995	21,557
Other liabilities	15,276	17,360
Total liabilities	701,418	763,115
Commitments and Contingencies (Note 13)
Equity
Common stock ($0.01 par value; 200,000 shares authorized; 75,611 and 61,942 shares issued and 75,134 and 61,465 outstanding as of June 30, 2017 and December 31, 2016, respectively)	751	615
Treasury stock, at cost (477 shares as of both June 30, 2017 and December 31, 2016)	(6,498)	(6,498)
Additional paid-in capital	649,382	581,975
Retained earnings	326,630	353,685
Accumulated other comprehensive income (loss)	18,243	21,884
Total equity	988,508	951,661
Total liabilities and equity	$ 1,689,926	$ 1,714,776