Financial Assets Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Restricted Cash and Cash Equivalents Items [Line Items]
Foreign currency derivative contracts	$ 1,469	$ (351)
Total financial assets	2,658,868	2,466,833
Money Market Funds
Restricted Cash and Cash Equivalents Items [Line Items]
Cash equivalents	169,894	303,780
Government And Corporate Debentures Fixed Interest Rate
Restricted Cash and Cash Equivalents Items [Line Items]
Marketable securities	1,941,781	1,624,096
US Government-sponsored Enterprises Debt Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Marketable securities	444,879	337,471
Government And Corporate Debentures Floating Interest Rate
Restricted Cash and Cash Equivalents Items [Line Items]
Marketable securities	98,148	195,759
Auction Rate Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Marketable securities	2,697	6,078
Fair Value, Inputs, Level 1
Restricted Cash and Cash Equivalents Items [Line Items]
Total financial assets	169,894	303,780
Fair Value, Inputs, Level 1 \| Money Market Funds
Restricted Cash and Cash Equivalents Items [Line Items]
Cash equivalents	169,894	303,780
Fair Value, Inputs, Level 2
Restricted Cash and Cash Equivalents Items [Line Items]
Foreign currency derivative contracts	1,469	(351)
Total financial assets	2,486,277	2,156,975
Fair Value, Inputs, Level 2 \| Government And Corporate Debentures Fixed Interest Rate
Restricted Cash and Cash Equivalents Items [Line Items]
Marketable securities	1,941,781	1,624,096
Fair Value, Inputs, Level 2 \| US Government-sponsored Enterprises Debt Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Marketable securities	444,879	337,471
Fair Value, Inputs, Level 2 \| Government And Corporate Debentures Floating Interest Rate
Restricted Cash and Cash Equivalents Items [Line Items]
Marketable securities	98,148	195,759
Fair Value, Inputs, Level 3
Restricted Cash and Cash Equivalents Items [Line Items]
Total financial assets	2,697	6,078
Fair Value, Inputs, Level 3 \| Auction Rate Securities
Restricted Cash and Cash Equivalents Items [Line Items]
Marketable securities	$ 2,697	$ 6,078

Amount of debt securities categorized neither as held-to-maturity nor trading.

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+ Details

- 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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