CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 107,948	$ 83,708
Accounts receivable	50,075	49,311
Due from related parties	122	0
Inventories, net (Note 4)	72,904	68,683
Derivative financial instruments (Note 6)	0	752
Income tax receivable	256	1,601
Other prepaid and deferred charges	36,964	20,361
Other assets	1,765	741
Total current assets	270,034	225,157
Noncurrent assets
Property, plant and equipment, net (Note 7)	1,365,755	1,432,361
Goodwill (Note 8)	2,280	2,280
Income tax receivable	29,454	0
Other assets	31,178	54,978
Total assets	1,698,701	1,714,776
Current liabilities
Accounts payable	29,832	27,678
Royalties and production taxes	54,327	63,018
Accrued expenses	32,818	35,857
Due to related parties	0	71
Other liabilities	2,435	2,567
Total current liabilities	119,412	129,191
Noncurrent liabilities
Senior notes (Note 11)	405,266	475,009
Asset retirement obligations, net of current portion (Note 14)	99,297	97,048
Accumulated postretirement benefit obligation, net of current portion (Note 16)	24,958	22,950
Royalties and production taxes	21,896	21,557
Other liabilities	20,063	17,360
Total liabilities	690,892	763,115
Commitments and Contingencies (Note 17)
Equity
Common stock ($0.01 par value; 200,000 shares authorized; 75,644 and 61,942 shares issued and 75,167 and 61,465 outstanding as of December 31, 2017 and December 31, 2016, respectively)	752	615
Treasury stock, at cost (477 shares as of both December 31, 2017 and December 31, 2016, respectively)	(6,498)	(6,498)
Additional paid-in capital	652,702	581,975
Retained earnings	347,046	353,685
Accumulated other comprehensive income (loss)	13,807	21,884
Total equity	1,007,809	951,661
Total liabilities and equity	$ 1,698,701	$ 1,714,776