Note 6 - Fair Value Measurements (Detail) - Fair Value Measurements at Reporting Date Using (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Investment Securities	$ 408,505	$ 337,473
Money Market Funds [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Cash Equivalents [Member]
Cash Equivalents	51,210	3,689
Money Market Funds [Member] \| Fair Value, Inputs, Level 1 [Member] \| Cash Equivalents [Member]
Cash Equivalents	51,210	3,689
Commercial Paper [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Short-term Investments [Member]
Investment Securities	140,693	81,767
Commercial Paper [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Cash Equivalents [Member]
Cash Equivalents	16,997	370
Commercial Paper [Member] \| Fair Value, Inputs, Level 2 [Member] \| Short-term Investments [Member]
Investment Securities	140,693	81,767
Commercial Paper [Member] \| Fair Value, Inputs, Level 2 [Member] \| Cash Equivalents [Member]
Cash Equivalents	16,997	370
US States and Political Subdivisions Debt Securities [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Short-term Investments [Member]
Investment Securities	118,460	106,207
US States and Political Subdivisions Debt Securities [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Long-Term Investments [Member]
Investment Securities	10,476	14,022
US States and Political Subdivisions Debt Securities [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Cash Equivalents [Member]
Cash Equivalents	25,113	70,245
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Short-term Investments [Member]
Investment Securities	118,460	106,207
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Long-Term Investments [Member]
Investment Securities	10,476	14,022
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Cash Equivalents [Member]
Cash Equivalents	25,113	70,245
Corporate Debt Securities [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Short-term Investments [Member]
Investment Securities	22,542	33,297
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Short-term Investments [Member]
Investment Securities	22,542	33,297
US Government Agencies Debt Securities [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Short-term Investments [Member]
Investment Securities	3,002	12,005
US Government Agencies Debt Securities [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Long-Term Investments [Member]
Investment Securities	20,012	10,008
US Government Agencies Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Short-term Investments [Member]
Investment Securities	3,002	12,005
US Government Agencies Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Long-Term Investments [Member]
Investment Securities	20,012	10,008
Certificates of Deposit [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member] \| Short-term Investments [Member]
Investment Securities		5,863
Certificates of Deposit [Member] \| Fair Value, Inputs, Level 2 [Member] \| Short-term Investments [Member]
Investment Securities		5,863
Estimate of Fair Value, Fair Value Disclosure [Member] \| Short-term Investments [Member]
Investment Securities	284,697	239,139
Estimate of Fair Value, Fair Value Disclosure [Member] \| Long-Term Investments [Member]
Investment Securities	30,488	24,030
Estimate of Fair Value, Fair Value Disclosure [Member] \| Cash Equivalents [Member]
Cash Equivalents	93,320	74,304
Estimate of Fair Value, Fair Value Disclosure [Member]
Investment Securities	408,505	337,473
Fair Value, Inputs, Level 1 [Member] \| Cash Equivalents [Member]
Cash Equivalents	51,210	3,689
Fair Value, Inputs, Level 1 [Member]
Investment Securities	51,210	3,689
Fair Value, Inputs, Level 2 [Member] \| Short-term Investments [Member]
Investment Securities	284,697	239,139
Fair Value, Inputs, Level 2 [Member] \| Long-Term Investments [Member]
Investment Securities	30,488	24,030
Fair Value, Inputs, Level 2 [Member] \| Cash Equivalents [Member]
Cash Equivalents	42,110	70,615
Fair Value, Inputs, Level 2 [Member]
Investment Securities	$ 357,295	$ 333,784

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 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 includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

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