Debt (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Summary of long-term debt
Revolving credit agreement	$ 10,000us-gaap_LongTermLineOfCredit	$ 15,000us-gaap_LongTermLineOfCredit
Fixed rate industrial development revenue bonds payable in annual installments through 2021	5,961	6,575
Variable rate industrial development revenue bonds payable in 2016	8,305	8,305
Total outstanding	24,266us-gaap_LongTermDebt	29,880us-gaap_LongTermDebt
Current portion of long-term debt	(653)us-gaap_LongTermDebtCurrent	(613)us-gaap_LongTermDebtCurrent
Total	$ 23,613us-gaap_LongTermDebtNoncurrent	$ 29,267us-gaap_LongTermDebtNoncurrent

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The carrying value as of the balance sheet date of the noncurrent portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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