Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 16,903	$ 12,483
Restricted cash (Note 8)	4,503	3,811
Certificates of deposit	493	1,495
Marketable securities	1,888	1,907
Accounts receivable	15,938	16,762
Prepaid income taxes	1,244	2,899
Inventory	29,542	12,804
Parts and supplies	10,775	10,043
Prepaid expenses	15,885	9,433
Total current assets	97,171	71,637
Property, plan and equipment, at cost:
Land and mineral rights	130,156	129,724
Buildings and equipment	375,626	356,911
Mine development	140,030	136,762
Total property, plan and equipment, at cost	645,812	623,397
Less - accumulated DD&A	(235,889)	(203,391)
Total property, plant and equipment, net	409,923	420,006
Equity method investments (Note 4)	3,654	11,890
Other assets (Note 5)	15,288	14,660
Total assets	526,036	518,193
Current liabilities:
Current portion of bank debt, net (Note 3)	23,555	33,171
Accounts payable and accrued liabilities (Note 6)	26,671	21,115
Total current liabilities	50,226	54,286
Long-term liabilities:
Bank debt, net (Note 3)	168,462	165,773
Deferred income taxes	28,608	28,728
Asset retirement obligations (ARO)	14,171	13,506
Other	7,184	6,577
Total long-term liabilities	218,425	214,584
Total liabilities	268,651	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	100,617	97,873
Retained earnings	152,467	150,236
Accumulated other comprehensive income (AOCI)		915
Total stockholders' equity	253,385	249,323
Total liabilities, redeemable noncontrolling interests, and stockholders' equity	$ 526,036	$ 518,193