Cash And Cash Equivalents And Investments (Summary Of Investments By Category) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Total investments, cost	$ 64,159	$ 136,113
Total investments, fair value	62,931	135,750
U.S. Treasury Securities [Member]
Available-for-sale securities, cost	3,430	24,500
Available-for-sale securities, fair value	3,429	24,511
U.S. Agency Securities [Member]
Available-for-sale securities, cost	8,110	35,407
Available-for-sale securities, fair value	8,074	35,387
Commercial Paper [Member]
Available-for-sale securities, cost		14,958
Available-for-sale securities, fair value		14,984
Corporate Notes/Bonds [Member]
Available-for-sale securities, cost	50,461	51,561
Available-for-sale securities, fair value	49,270	51,181
Certificates/Term Deposits [Member]
Available-for-sale securities, cost	2,158	9,687
Available-for-sale securities, fair value	$ 2,158	$ 9,687

- 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.