Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	$ 523,131	$ 180,909
Total	1,008,823	754,645
Contingent consideration	16,513	68,892
Derivatives, Liabilities	106	314
Liabilities	16,619	69,206
Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and Cash equivalents	194,724	161,243
Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and Cash equivalents	290,968	412,493
U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	268,020	14,180
U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	146,655	83,197
Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	47,490	44,829
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	44,476	22,075
Equity And Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	9,552	8,237
Certificates Of Deposit And Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	6,660	8,117
Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	278	274
Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	748,120	580,263
Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and Cash equivalents	194,724	161,243
Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and Cash equivalents	275,546	396,329
Quoted Prices in Active Markets for Identical Instruments (Level 1) \| U.S. Treasury Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	268,020	14,180
Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Equity And Debt Mutual Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	9,552	8,237
Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Non-U.S. Government Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	278	274
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	260,703	174,382
Derivatives, Liabilities	106	314
Liabilities	106	314
Significant Other Observable Inputs (Level 2) \| Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash and Cash equivalents	15,422	16,164
Significant Other Observable Inputs (Level 2) \| U.S. Government Agency Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	146,655	83,197
Significant Other Observable Inputs (Level 2) \| Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	47,490	44,829
Significant Other Observable Inputs (Level 2) \| Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	44,476	22,075
Significant Other Observable Inputs (Level 2) \| Certificates Of Deposit And Time Deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Available for sale securities	6,660	8,117
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Contingent consideration	16,513	68,892
Liabilities	$ 16,513	$ 68,892

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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Fair value, as of the acquisition date, of potential payments under the contingent consideration arrangement including cash and shares.

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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.

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- Definition

Fair values as of the balance sheet date of all liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

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