Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments [Line Items]
Adjusted Cost	$ 189,691	$ 178,115
Unrealized Gains	64	14
Unrealized Losses	(209)	(210)
Total Fair Value	189,546	177,919
Fair Value of Investments in Unrealized Loss Position	29,004	40,451
Money Market Funds [Member]
Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments [Line Items]
Adjusted Cost	31,135	60,078
Total Fair Value	31,135	60,078
Certificates of Deposit [Member]
Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments [Line Items]
Adjusted Cost	22,008	22,778
Total Fair Value	22,008	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	130,978	89,689
Unrealized Gains	64	14
Unrealized Losses	(3)	(29)
Total Fair Value	131,039	89,674
Fair Value of Investments in Unrealized Loss Position	23,640	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	(206)	(181)
Total Fair Value	5,364	5,389
Fair Value of Investments in Unrealized Loss Position	$ 5,364	$ 5,389