CONDENSED CONSOLIDATED BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 60,469	$ 58,332
Trade receivables, net	16,028us-gaap_AccountsReceivableNetCurrent	17,444us-gaap_AccountsReceivableNetCurrent
Inventories	13,886us-gaap_InventoryNet	13,436us-gaap_InventoryNet
Prepaid expenses and other current assets	1,757	2,550
Total current assets	92,140us-gaap_AssetsCurrent	91,762us-gaap_AssetsCurrent
Property, plant and equipment	265,022us-gaap_PropertyPlantAndEquipmentGross	262,462us-gaap_PropertyPlantAndEquipmentGross
Less accumulated depreciation and depletion	(157,146)	(153,949)
Property, plant and equipment, net	107,876us-gaap_PropertyPlantAndEquipmentNet	108,513us-gaap_PropertyPlantAndEquipmentNet
Other assets, net	134us-gaap_OtherAssetsNoncurrent	145us-gaap_OtherAssetsNoncurrent
Total assets	200,150us-gaap_Assets	200,420us-gaap_Assets
Current liabilities:
Current installments of debt	15,417us-gaap_LongTermDebtCurrent	16,667us-gaap_LongTermDebtCurrent
Accounts payable	4,656us-gaap_AccountsPayableCurrent	5,166us-gaap_AccountsPayableCurrent
Accrued expenses	2,547us-gaap_AccruedLiabilitiesCurrent	3,132us-gaap_AccruedLiabilitiesCurrent
Total current liabilities	22,620us-gaap_LiabilitiesCurrent	24,965us-gaap_LiabilitiesCurrent
Deferred tax liabilities, net	19,331	19,259
Other liabilities	1,539us-gaap_OtherLiabilitiesNoncurrent	1,505us-gaap_OtherLiabilitiesNoncurrent
Total liabilities	43,490us-gaap_Liabilities	45,729us-gaap_Liabilities
Stockholders' equity:
Common stock	653us-gaap_CommonStockValue	652us-gaap_CommonStockValue
Additional paid-in capital	20,686	20,418
Accumulated other comprehensive loss	(911)	(1,024)
Retained earnings	186,375	184,710
Less treasury stock, at cost	(50,143)us-gaap_TreasuryStockValue	(50,065)us-gaap_TreasuryStockValue
Total stockholders' equity	156,660us-gaap_StockholdersEquity	154,691us-gaap_StockholdersEquity
Total liabilities and stockholders' equity	$ 200,150	$ 200,420

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19

-Subparagraph a

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682