Note 3 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Note 3 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments [Line Items]
Adjusted Cost	$ 182,482	$ 178,115
Unrealized Gains	4	14
Unrealized Losses	(379)	(210)
Total Fair Value	182,107	177,919
Fair Value of Investments in Unrealized Loss Position	116,081	40,451
Money Market Funds [Member]
Note 3 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments [Line Items]
Adjusted Cost	31,640	60,078
Total Fair Value	31,640	60,078
Certificates of Deposit [Member]
Note 3 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments [Line Items]
Adjusted Cost	21,574	22,778
Total Fair Value	21,574	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	123,698	89,689
Unrealized Gains	4	14
Unrealized Losses	(170)	(29)
Total Fair Value	123,532	89,674
Fair Value of Investments in Unrealized Loss Position	110,720	35,062
Auction Rate Securities [Member]
Note 3 - Cash, Cash Equivalents and Investments (Details) - Unrealized Gains and Losses on Investments [Line Items]
Adjusted Cost	5,570	5,570
Unrealized Losses	(209)	(181)
Total Fair Value	5,361	5,389
Fair Value of Investments in Unrealized Loss Position	$ 5,361	$ 5,389