Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments [Line Items]
Adjusted Cost	$ 190,310	$ 178,115
Unrealized Gains	36	14
Unrealized Losses	(196)	(210)
Total Fair Value	190,150us-gaap_AvailableForSaleSecurities	177,919us-gaap_AvailableForSaleSecurities
Fair Value of Investments in Unrealized Loss Position	39,426	40,451
Money Market Funds [Member]
Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments [Line Items]
Adjusted Cost	46,965	60,078
Total Fair Value	46,965	60,078
Certificates of Deposit [Member]
Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments [Line Items]
Adjusted Cost	23,050	22,778
Total Fair Value	23,050	22,778
US Government Agencies Short-term Debt Securities [Member]
Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments [Line Items]
Adjusted Cost	114,725	89,689
Unrealized Gains	36	14
Unrealized Losses	(20)	(29)
Total Fair Value	114,741	89,674
Fair Value of Investments in Unrealized Loss Position	34,032	35,062
Auction Rate Securities [Member]
Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains And Losses On Investments [Line Items]
Adjusted Cost	5,570	5,570
Unrealized Losses	(176)	(181)
Total Fair Value	5,394	5,389
Fair Value of Investments in Unrealized Loss Position	$ 5,394	$ 5,389

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

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