Schedule of Available for Sale Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 663,625	$ 178,625
Available-for-sale marketable securities, Unrealized Gain	3,862	2,581
Available-for-sale marketable securities, Unrealized (Loss)	(99)	(297)
Available-for-sale marketable securities, Fair Market Value	667,388	180,909
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	59,100	64,571
U.S. Treasury Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	311,915	14,141
Available-for-sale marketable securities, Unrealized Gain	216	39
Available-for-sale marketable securities, Unrealized (Loss)	(15)
Available-for-sale marketable securities, Fair Market Value	312,116	14,180
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	1,018
U.S. Government Agency Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	217,396	83,070
Available-for-sale marketable securities, Unrealized Gain	262	152
Available-for-sale marketable securities, Unrealized (Loss)	(3)	(25)
Available-for-sale marketable securities, Fair Market Value	217,655	83,197
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	9,018	28,510
Commercial Paper
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	70,431	22,083
Available-for-sale marketable securities, Unrealized Gain	9	2
Available-for-sale marketable securities, Unrealized (Loss)	(6)	(10)
Available-for-sale marketable securities, Fair Market Value	70,434	22,075
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	25,209	9,479
Corporate Debt Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	53,405	43,077
Available-for-sale marketable securities, Unrealized Gain	2,414	1,893
Available-for-sale marketable securities, Unrealized (Loss)	(64)	(141)
Available-for-sale marketable securities, Fair Market Value	55,755	44,829
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	23,255	17,033
Equity And Debt Mutual Funds
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	8,767	7,876
Available-for-sale marketable securities, Unrealized Gain	961	477
Available-for-sale marketable securities, Unrealized (Loss)	(11)	(116)
Available-for-sale marketable securities, Fair Market Value	9,717	8,237
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	600	3,749
Certificates Of Deposit And Time Deposits
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	1,627	8,122
Available-for-sale marketable securities, Unrealized (Loss)		(5)
Available-for-sale marketable securities, Fair Market Value	1,627	8,117
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses		5,800
Non-U.S. Government Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	84	256
Available-for-sale marketable securities, Unrealized Gain		18
Available-for-sale marketable securities, Fair Market Value	$ 84	$ 274

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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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 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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- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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