Note 3 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Note 3 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments [Line Items]
Adjusted Cost	$ 178,115	$ 173,931
Unrealized Gains	14	26
Unrealized Losses	(210)	(383)
Total Fair Value	177,919us-gaap_AvailableForSaleSecurities	173,574us-gaap_AvailableForSaleSecurities
Fair Value of Investments in Unrealized Loss Position	40,451	52,740
Money Market Funds [Member]
Note 3 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments [Line Items]
Adjusted Cost	60,078	35,588
Total Fair Value	60,078	35,588
Certificates of Deposit [Member]
Note 3 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments [Line Items]
Adjusted Cost	22,778
Total Fair Value	22,778
US Government Agencies Short-term Debt Securities [Member]
Note 3 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments [Line Items]
Adjusted Cost	89,689	128,123
Unrealized Gains	14	26
Unrealized Losses	(29)	(23)
Total Fair Value	89,674	128,126
Fair Value of Investments in Unrealized Loss Position	35,062	42,880
Auction Rate Securities [Member]
Note 3 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments [Line Items]
Adjusted Cost	5,570	10,220
Unrealized Losses	(181)	(360)
Total Fair Value	5,389	9,860
Fair Value of Investments in Unrealized Loss Position	$ 5,389	$ 9,860

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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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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Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

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Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities.

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