Summary of Significant Accounting Policies (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value of Financial Instruments
Financial assets carried at fair value, total	$ 134,098	$ 112,030
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value of Financial Instruments
Financial assets carried at fair value, total	40	1,819
Quoted Prices in Active Markets for Identical Assets (Level 1) \| Equity securities
Fair Value of Financial Instruments
Financial assets carried at fair value, total	40	1,819
Significant Other Observable Inputs (Level 2)
Fair Value of Financial Instruments
Financial assets carried at fair value, total	134,058	110,211
Significant Other Observable Inputs (Level 2) \| Money market funds
Fair Value of Financial Instruments
Financial assets carried at fair value, total	1,033	4,469
Significant Other Observable Inputs (Level 2) \| Commercial paper
Fair Value of Financial Instruments
Financial assets carried at fair value, total	36,539	31,394
Significant Other Observable Inputs (Level 2) \| Corporate notes
Fair Value of Financial Instruments
Financial assets carried at fair value, total	11,353	1,435
Significant Other Observable Inputs (Level 2) \| U.S. government and U.S government agency notes
Fair Value of Financial Instruments
Financial assets carried at fair value, total	85,133	72,913
Significant Unobservable Inputs (Level 3)
Fair Value of Financial Instruments
Financial liabilities carried at fair value, total	17,252	29,164
Significant Unobservable Inputs (Level 3) \| Warrant liability
Fair Value of Financial Instruments
Financial liabilities carried at fair value, total	276	187
Significant Unobservable Inputs (Level 3) \| Deferred acquisition consideration
Fair Value of Financial Instruments
Financial liabilities carried at fair value, total	16,976	28,977
Total
Fair Value of Financial Instruments
Financial assets carried at fair value, total	134,098	112,030
Financial liabilities carried at fair value, total	17,252	29,164
Total \| Warrant liability
Fair Value of Financial Instruments
Financial liabilities carried at fair value, total	276	187
Total \| Deferred acquisition consideration
Fair Value of Financial Instruments
Financial liabilities carried at fair value, total	16,976	28,977
Total \| Money market funds
Fair Value of Financial Instruments
Financial assets carried at fair value, total	1,033	4,469
Total \| Commercial paper
Fair Value of Financial Instruments
Financial assets carried at fair value, total	36,539	31,394
Total \| Corporate notes
Fair Value of Financial Instruments
Financial assets carried at fair value, total	11,353	1,435
Total \| U.S. government and U.S government agency notes
Fair Value of Financial Instruments
Financial assets carried at fair value, total	85,133	72,913
Total \| Equity securities
Fair Value of Financial Instruments
Financial assets carried at fair value, total	$ 40	$ 1,819

- 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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