Short-Term Investments (Schedule Of Summary Of Short-Term Investments) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	$ 337,639	$ 277,271
Available-for-Sale Securities, Gross Unrealized Gains	1,084	944
Unrealized Losses, Total	(294)	(73)
Available-for-Sale Securities, Estimated Fair Value	338,429	278,142
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	62,131	46,234
Available-for-Sale Securities, Gross Unrealized Gains	3	4
Unrealized Losses, Total	(5)
Available-for-Sale Securities, Estimated Fair Value	62,129	46,238
Obligations Of U.S. Government-Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	73,984	37,826
Available-for-Sale Securities, Gross Unrealized Gains	342	191
Unrealized Losses, Total	(99)	(50)
Available-for-Sale Securities, Estimated Fair Value	74,227	37,967
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	199,814	191,680
Available-for-Sale Securities, Gross Unrealized Gains	739	743
Unrealized Losses, Total	(189)	(23)
Available-for-Sale Securities, Estimated Fair Value	200,364	192,400
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale Securities, Amortized Cost	1,710	1,531
Available-for-Sale Securities, Gross Unrealized Gains		6
Unrealized Losses, Total	(1)
Available-for-Sale Securities, Estimated Fair Value	$ 1,709	$ 1,537

- 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.

+ References+ Details