CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 89,313	$ 168,745
Accounts receivable	43,248	86,838
Due from related parties	160	227
Inventories, net (Note 5)	76,763	79,802
Deferred income taxes (Note 18)	0	21,670
Derivative financial instruments (Note 7)	0	17,111
Income tax receivable	8,659	3
Other prepaids and deferred charges	25,945	8,828
Other assets	98	1,009
Total current assets	244,186	384,233
Noncurrent assets
Property, plant and equipment, net (Note 8)	1,488,371	1,589,138
Port access rights, net (Note 10)	0	53,780
Goodwill (Note 9)	2,280	35,634
Deferred income taxes (Note 18)	0	56,468
Other assets	67,323	31,900
Total assets	1,802,160	2,151,153
Current liabilities
Accounts payable	44,385	52,035
Royalties and production taxes	74,054	86,908
Accrued expenses	42,317	52,213
Federal coal lease obligations (Note 14)	0	63,970
Other liabilities	2,133	1,632
Total current liabilities	162,889	256,758
Noncurrent liabilities
Senior notes (Note 13)	491,160	489,715
Asset retirement obligations, net of current portion (Note 17)	151,755	216,241
Accumulated postretirement benefit obligation, net of current portion (Note 19)	60,845	50,276
Royalties and production taxes	34,680	39,304
Other liabilities	12,950	11,025
Total liabilities	$ 914,279	$ 1,063,319
Commitments and Contingencies (Note 20)
Equity
Common stock ($0.01 par value; 200,000 shares authorized; 61,647 and 61,454 shares issued and 61,170 and 61,022 outstanding at December 31, 2015 and December 31, 2014, respectively)	$ 612	$ 610
Treasury stock, at cost (477 shares and 432 shares at December 31, 2015 and December 31, 2014, respectively)	(6,498)	(6,243)
Additional paid-in capital	574,874	568,022
Retained earnings	331,844	536,744
Accumulated other comprehensive income (loss)	(12,951)	(11,299)
Total equity	887,881	1,087,834
Total liabilities and equity	$ 1,802,160	$ 2,151,153