Fair Value of Financial Instruments (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Assets:
Marketable securities	$ 37,940,000us-gaap_MarketableSecuritiesCurrent	$ 49,211,000us-gaap_MarketableSecuritiesCurrent
Long term marketable securities	19,816,000us-gaap_LongTermInvestments	8,756,000us-gaap_LongTermInvestments
Liabilities:
Derivative liabilities	6,564,000us-gaap_DerivativeLiabilitiesNoncurrent	12,644,000us-gaap_DerivativeLiabilitiesNoncurrent
Quoted Prices in Active Markets (Level 1)
Assets:
Cash and cash equivalents	36,396,000	32,980,000
Total assets at fair value	36,396,000	32,980,000
Significant Other Observable Inputs (Level 2)
Assets:
Marketable securities	37,940,000	49,211,000
Long term marketable securities	19,816,000	8,756,000
Marketable securities - restricted (SERP)	305,000	305,000
Total assets at fair value	58,061,000	58,272,000
Significant Unobservable Inputs (Level 3)
Liabilities:
Derivative liabilities	6,564,000	12,644,000
Total Carrying Value
Assets:
Cash and cash equivalents	36,396,000	32,980,000
Marketable securities	37,940,000	49,211,000
Long term marketable securities	19,816,000	8,756,000
Marketable securities - restricted (SERP)	305,000	305,000
Total assets at fair value	94,457,000	91,252,000
Liabilities:
Derivative liabilities	$ 6,564,000	$ 12,644,000

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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For a classified balance sheet, the amount recognized in balance sheet as a current asset associated with the plan.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled after one year or the normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

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The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle).

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Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

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