Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments [Line Items]
Adjusted Cost	$ 190,405	$ 178,115
Unrealized Gains	39	14
Unrealized Losses	(214)	(210)
Total Fair Value	190,230	177,919
Fair Value of Investments in Unrealized Loss Position	51,019	40,451
Money Market Funds [Member]
Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments [Line Items]
Adjusted Cost	34,689	60,078
Total Fair Value	34,689	60,078
Certificates of Deposit [Member]
Note 9 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments [Line Items]
Adjusted Cost	23,093	22,778
Total Fair Value	23,093	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	127,053	89,689
Unrealized Gains	39	14
Unrealized Losses	(19)	(29)
Total Fair Value	127,073	89,674
Fair Value of Investments in Unrealized Loss Position	45,644	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	(195)	(181)
Total Fair Value	5,375	5,389
Fair Value of Investments in Unrealized Loss Position	$ 5,375	$ 5,389