Note 6 - Marketable Securities (Detail) - Portfolio of marketable securities: (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2013	Dec. 31, 2012
Available-for-sale securities:
Available-for-sale securities cost	$ 242,505	$ 250,088
Available-for-sale securities gross unrealized gains	6,718	3,184
Available-for-sale securities gross unrealized losses	(1,158)	(2,257)
Available-for-sale securities estimated fair value	248,065	251,015
Cash equivalents cost	(61,727)	(51,887)
Cash equivalents estimated fair value	(61,727)	(51,887)
Marketable securities cost	180,778	198,201
Marketable securities unrealized gains	6,718	3,184
Marketable securities unrealized losses	(1,158)	(2,257)
Marketable securities estimated fair value	186,338	199,128
Short-term Deposits [Member]
Available-for-sale securities:
Available-for-sale securities cost	47,490	48,596
Available-for-sale securities estimated fair value	47,490	48,596
Mutual Funds [Member]
Available-for-sale securities:
Available-for-sale securities cost	10,368	10,368
Available-for-sale securities gross unrealized gains	2,724	1,452
Available-for-sale securities estimated fair value	13,092	11,820
US Treasury Securities [Member]
Available-for-sale securities:
Available-for-sale securities cost	78,346	99,299
Available-for-sale securities gross unrealized gains	131	178
Available-for-sale securities estimated fair value	78,477	99,477
Corporate Securities [Member]
Available-for-sale securities:
Available-for-sale securities cost	30,387	20,842
Available-for-sale securities gross unrealized gains	2,829	1,255
Available-for-sale securities gross unrealized losses	(686)	(1,980)
Available-for-sale securities estimated fair value	32,530	20,117
Corporate Obligations [Member]
Available-for-sale securities:
Available-for-sale securities cost	54,373	48,708
Available-for-sale securities gross unrealized gains	1,029	283
Available-for-sale securities gross unrealized losses	(472)	(277)
Available-for-sale securities estimated fair value	54,930	48,714
Commercial Paper [Member]
Available-for-sale securities:
Available-for-sale securities cost	21,541	22,275
Available-for-sale securities gross unrealized gains	5	16
Available-for-sale securities estimated fair value	$ 21,546	$ 22,291

Estimated fair value of marketable securities.

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- Definition

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.

+ References

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-SubTopic 10

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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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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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Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Total debt and equity financial instruments including: (1) securities held-to-maturity, (2) trading securities, and (3) securities available-for-sale.

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The increase (decrease), resulting in a gain, in the difference between the fair value and the carrying value, or in the comparative fair values, of securities held at each balance sheet date, that was included in earnings for the period.

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