Marketable Securities and Investments (Schedule of Contractual Maturities of Marketable Securities and Other Investment Related Assets) (Details) (Money Market Funds [Member], USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities due in 1 year or less	$ 331,967	$ 375,005
Available-for-sale securities due after 1 year through 5 years	384,654	499,275
Available-for-sale securities due after 10 years	118,775	137,256
Total Available-for-sale securities	$ 835,396	$ 1,011,536

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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