Schedule of Reported 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
Marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	344,777,000	96,518,000
Available-for-sale marketable securities, Unrealized Gain	77,000	24,000
Available-for-sale marketable securities, Unrealized (Loss)	(4,000)	(40,000)
Available-for-sale marketable securities, Fair Market Value	344,850,000	96,502,000
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	10,235,000	35,595,000
Long-term marketable securities
Schedule of Available-for-sale Securities
Available-for-sale marketable securities, Cost	174,211,000	82,107,000
Available-for-sale marketable securities, Unrealized Gain	4,131,000	2,557,000
Available-for-sale marketable securities, Unrealized (Loss)	(61,000)	(257,000)
Available-for-sale marketable securities, Fair Market Value	178,281,000	84,407,000
Available-for-sale marketable securities, Fair Market Value of Investments with Unrealized Losses	$ 1,195,000	$ 28,976,000

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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