Fair Value Measurements (Details) (USD $) In Thousands	9 Months Ended
Sep. 30, 2011	Dec. 31, 2010
Liabilities:
Contingent purchase price	$ 28,204	$ 25,387
Transfer of Assets Between Level 1 and Level 2	0
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance of the Fair Value of Level 3 Inputs	25,387
Fair Value Adjustment to Unobservable Inputs Included in Net Income	2,817
Ending Balance of the Fair Value of Level 3 Inputs	28,204
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Assets:
Money market	16,540
US treasury notes	3,056
U.S. government agency notes	0
Corporate debt securities	0
Total assets at fair value	19,596
Liabilities:
Contingent purchase price	0
Total liabilities at fair value	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Assets:
Money market	0
US treasury notes	0
U.S. government agency notes	14,919
Corporate debt securities	31,764
Total assets at fair value	46,683
Liabilities:
Contingent purchase price	0
Total liabilities at fair value	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets:
Money market	0
US treasury notes	0
U.S. government agency notes	0
Corporate debt securities	0
Total assets at fair value	0
Liabilities:
Contingent purchase price	28,204
Total liabilities at fair value	28,204
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Assets:
Money market	16,540
US treasury notes	3,056
U.S. government agency notes	14,919
Corporate debt securities	31,764
Total assets at fair value	66,279
Liabilities:
Contingent purchase price	28,204
Total liabilities at fair value	$ 28,204

Noncurrent portion of the fair value, as of the balance sheet date, of potential payments under the contingent consideration arrangements.

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Corporate Debt Securities Fair Value Disclosure

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US Treasury Notes Fair Value Disclosure

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- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

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- 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 includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The amount of the transfers of assets or liabilities measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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-Name Accounting Standards Codification

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- Definition

This element represents total gains or losses for the period (realized and unrealized), arising from assets measured at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or resulted in a change in net asset value.

+ References

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- Definition

This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

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- Definition

The fair value as of the balance sheet date of firm holdings in debt obligations issued by the US government including short-term Treasury bills, medium-term Treasury notes, and long-term Treasury bonds, as well as debt issued by agencies. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

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- Definition

This element represents the aggregate of the liabilities reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

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