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Cash, Cash Equivalents and Short-Term Investments (Details 2) (Fair Value, Recurring [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair value assets measurements on a recurring basis
Asset measured at fair value	$ 106,622	$ 105,002
Cash [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	24,877	25,359
U.S. Treasury securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value		3,267
Corporate debt securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	21,060	27,208
Municipal securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	6,570	4,315
Government-sponsored enterprise securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	22,899	19,050
Money market funds [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	29,717	22,753
Bank certificates of deposit [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	1,499	3,050
Level 1 [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	24,877	28,626
Level 1 [Member] \| Cash [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	24,877	25,359
Level 1 [Member] \| U.S. Treasury securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value		3,267
Level 2 [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	81,745	76,376
Level 2 [Member] \| Corporate debt securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	21,060	27,208
Level 2 [Member] \| Municipal securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	6,570	4,315
Level 2 [Member] \| Government-sponsored enterprise securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	22,899	19,050
Level 2 [Member] \| Money market funds [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	29,717	22,753
Level 2 [Member] \| Bank certificates of deposit [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value	1,499	3,050
Level 3 [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value
Level 3 [Member] \| Cash [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value
Level 3 [Member] \| U.S. Treasury securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value
Level 3 [Member] \| Corporate debt securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value
Level 3 [Member] \| Municipal securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value
Level 3 [Member] \| Government-sponsored enterprise securities [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value
Level 3 [Member] \| Money market funds [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value
Level 3 [Member] \| Bank certificates of deposit [Member]
Fair value assets measurements on a recurring basis
Asset measured at fair value

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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