Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 10,185	$ 12,483
Restricted cash (Note 8)	4,234	3,811
Certificates of deposit	735	1,495
Marketable securities	1,791	1,907
Accounts receivable	11,627	16,762
Prepaid income taxes	2,540	2,899
Coal inventory	34,373	12,804
Parts and supply inventory	11,487	10,043
Prepaid expenses	15,633	9,433
Total current assets	92,605	71,637
Property, plan and equipment, at cost:
Land and mineral rights	130,860	129,724
Buildings and equipment	368,220	356,911
Mine development	138,467	136,762
Total property, plan and equipment, at cost	637,547	623,397
Less - accumulated DD&A	(225,231)	(203,391)
Total property, plant and equipment, net	412,316	420,006
Equity method investments (Note 4)	3,697	11,890
Other assets (Note 5)	14,798	14,660
Total assets	523,416	518,193
Current liabilities:
Current portion of bank debt, net (Note 3)	21,749	33,171
Accounts payable and accrued liabilities (Note 6)	25,785	21,115
Total current liabilities	47,534	54,286
Long-term liabilities:
Bank debt, net (Note 3)	170,362	165,773
Deferred income taxes	28,993	28,728
Asset retirement obligations (ARO)	14,077	13,506
Other	7,132	6,577
Total long-term liabilities	220,564	214,584
Total liabilities	268,098	268,870
Redeemable noncontrolling interests (Note 13)	4,000
Stockholders' equity:
Preferred stock, $.10 par value, 10,000 shares authorized; none issued
Common stock, $.01 par value, 100,000 shares authorized; 30,177 and 29,955 shares outstanding, respectively	301	299
Additional paid-in capital	100,228	97,873
Retained earnings	150,789	150,236
Accumulated other comprehensive income (AOCI)		915
Total stockholders' equity	251,318	249,323
Total liabilities, redeemable noncontrolling interests, and stockholders' equity	$ 523,416	$ 518,193