Schedule of Available for Sale Marketable Securities (Detail) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	$ 518,988,000	$ 178,625,000
Available-for-sale marketable securities, Unrealized Gain	4,208,000	2,581,000
Available-for-sale marketable securities, Unrealized (Loss)	(65,000)	(297,000)
Available-for-sale marketable securities, Fair Market Value	523,131,000	180,909,000
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	11,430,000	64,571,000
U.S. Treasury Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	267,831,000	14,141,000
Available-for-sale marketable securities, Unrealized Gain	190,000	39,000
Available-for-sale marketable securities, Unrealized (Loss)	(1,000)
Available-for-sale marketable securities, Fair Market Value	268,020,000	14,180,000
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	175,000
U.S. Government Agency Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	146,418,000	83,070,000
Available-for-sale marketable securities, Unrealized Gain	237,000	152,000
Available-for-sale marketable securities, Unrealized (Loss)		(25,000)
Available-for-sale marketable securities, Fair Market Value	146,655,000	83,197,000
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses		28,510,000
Corporate Debt Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	44,858,000	43,077,000
Available-for-sale marketable securities, Unrealized Gain	2,689,000	1,893,000
Available-for-sale marketable securities, Unrealized (Loss)	(57,000)	(141,000)
Available-for-sale marketable securities, Fair Market Value	47,490,000	44,829,000
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	872,000	17,033,000
Commercial Paper
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	44,474,000	22,083,000
Available-for-sale marketable securities, Unrealized Gain	6,000	2,000
Available-for-sale marketable securities, Unrealized (Loss)	(4,000)	(10,000)
Available-for-sale marketable securities, Fair Market Value	44,476,000	22,075,000
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	10,235,000	9,479,000
Equity And Debt Mutual Funds
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	8,471,000	7,876,000
Available-for-sale marketable securities, Unrealized Gain	1,084,000	477,000
Available-for-sale marketable securities, Unrealized (Loss)	(3,000)	(116,000)
Available-for-sale marketable securities, Fair Market Value	9,552,000	8,237,000
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	148,000	3,749,000
Certificates Of Deposit And Time Deposits
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	6,658,000	8,122,000
Available-for-sale marketable securities, Unrealized Gain	2,000
Available-for-sale marketable securities, Unrealized (Loss)		(5,000)
Available-for-sale marketable securities, Fair Market Value	6,660,000	8,117,000
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses		5,800,000
Non-U.S. Government Securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	278,000	256,000
Available-for-sale marketable securities, Unrealized Gain		18,000
Available-for-sale marketable securities, Fair Market Value	$ 278,000	$ 274,000

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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