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Marketable Securities	9 Months Ended
Marketable Securities	Sep. 30, 2012
Marketable Securities [Abstract]
Marketable Securities	Marketable Securities Marketable securities consist primarily of corporate bonds 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- and nine-month periods ended September 30, 2012, the amortization of bond premiums totals $182 and $710, respectively, compared to $234 and $898, respectively, for the comparable periods in 2011. The values of these securities may fluctuate as a result of changes in equity values, market interest rates and credit risk.