Marketable Securities Classified as Available-for-Sale (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 117,861	$ 215,260
Gross Unrealized Gain	372	19
Gross Unrealized Loss	(46)	(335)
Fair Value	118,187	214,944
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	49,545	68,196
Gross Unrealized Gain	203
Gross Unrealized Loss	(4)	(209)
Fair Value	49,744	67,987
Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,431	60,602
Gross Unrealized Gain	43
Gross Unrealized Loss	(27)	(64)
Fair Value	23,447	60,538
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,079	37,130
Gross Unrealized Gain	70
Gross Unrealized Loss		(33)
Fair Value	23,149	37,097
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,064	17,448
Gross Unrealized Gain	40
Gross Unrealized Loss	(15)	(24)
Fair Value	12,089	17,424
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,200	22,266
Gross Unrealized Gain		5
Fair Value	1,200	22,271
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,273	7,200
Gross Unrealized Gain	13	14
Fair Value	6,286	7,214
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,003	2,019
Gross Unrealized Gain	1
Gross Unrealized Loss		(3)
Fair Value	1,004	2,016
Floating rate notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,266	327
Gross Unrealized Gain	2
Gross Unrealized Loss		(2)
Fair Value	1,268	325
Collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		72
Fair Value		$ 72

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 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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