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Marketable Securities
3 Months Ended
Mar. 31, 2013
Marketable Securities [Abstract]  
Marketable Securities
Marketable Securities
Marketable securities consist primarily of corporate bonds and certificates of deposit with maturities greater than three months and up to ten years at the time of purchase as well as marketable equity securities. These securities, which are classified as available-for-sale, are carried at fair value, with unrealized gains and losses, net of any tax effect, reported in stockholders’ equity as accumulated other comprehensive income (loss). These securities are classified as current and non-current marketable securities based upon their maturities. Amortization of premiums and discounts is included in interest income. For the three months ended March 31, 2013 and 2012, the amortization of bond premiums totals $187 and $250 respectively. The values of these securities may fluctuate as a result of changes in equity values, market interest rates and credit risk.