CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 109,459	$ 107,948
Accounts receivable	62,266	50,075
Due from related parties	1,609	122
Inventories, net	69,474	72,904
Derivative financial instruments	730	0
Income tax receivable	14,727	256
Other prepaid and deferred charges	20,320	36,964
Other assets	806	1,765
Total current assets	279,391	270,034
Noncurrent assets
Property, plant and equipment, net	1,333,642	1,365,755
Goodwill	2,280	2,280
Income tax receivable	14,727	29,454
Other assets	40,356	31,178
Total assets	1,670,396	1,698,701
Current liabilities
Accounts payable	40,969	29,832
Royalties and production taxes	56,088	54,327
Accrued expenses	39,085	32,818
Current portion of federal coal lease obligations	379	0
Other liabilities	1,707	2,435
Total current liabilities	138,228	119,412
Noncurrent liabilities
Senior notes	401,914	405,266
Federal coal lease obligations, net of current portion	1,404	0
Asset retirement obligations, net of current portion	108,359	99,297
Accumulated postretirement medical benefit obligation, net of current portion	0	24,958
Royalties and production taxes	27,079	21,896
Other liabilities	6,597	20,063
Total liabilities	683,581	690,892
Commitments and Contingencies (Note 17)
Equity
Common stock ($0.01 par value; 200,000 shares authorized; 76,255 and 75,644 shares issued and 75,778 and 75,167 outstanding as of September 30, 2018 and December 31, 2017, respectively)	758	752
Treasury stock, at cost (477 shares as of both September 30, 2018 and December 31, 2017)	(6,498)	(6,498)
Additional paid-in capital	655,605	652,702
Retained earnings	322,248	347,046
Accumulated other comprehensive income (loss)	14,702	13,807
Total equity	986,815	1,007,809
Total liabilities and equity	$ 1,670,396	$ 1,698,701