CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 120,942	$ 83,708
Accounts receivable	53,702	49,311
Due from related parties	1,169	0
Inventories, net	69,780	68,683
Derivative financial instruments	0	752
Income tax receivable	1,145	1,601
Other prepaid and deferred charges	31,978	20,361
Other assets	1,762	741
Total current assets	280,478	225,157
Noncurrent assets
Property, plant and equipment, net	1,394,056	1,432,361
Goodwill	2,280	2,280
Other assets	37,307	54,978
Total assets	1,714,121	1,714,776
Current liabilities
Accounts payable	29,288	27,678
Royalties and production taxes	59,251	63,018
Accrued expenses	39,892	35,857
Due to related parties	0	71
Other liabilities	2,555	2,567
Total current liabilities	130,986	129,191
Noncurrent liabilities
Senior notes	410,374	475,009
Asset retirement obligations, net of current portion	111,211	97,048
Accumulated postretirement medical benefit obligation, net of current portion	24,101	22,950
Royalties and production taxes	29,650	21,557
Other liabilities	16,839	17,360
Total liabilities	723,161	763,115
Commitments and Contingencies (Note 13)
Equity
Common stock ($0.01 par value; 200,000 shares authorized; 75,619 and 61,942 shares issued and 75,142 and 61,465 outstanding as of September 30, 2017 and December 31, 2016, respectively)	751	615
Treasury stock, at cost (477 shares as of both September 30, 2017 and December 31, 2016)	(6,498)	(6,498)
Additional paid-in capital	651,078	581,975
Retained earnings	329,207	353,685
Accumulated other comprehensive income (loss)	16,422	21,884
Total equity	990,960	951,661
Total liabilities and equity	$ 1,714,121	$ 1,714,776