Note 9 - Financial Assets and Liabilities, Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	$ 27,864	$ 31,640
Money Market Funds [Member]
Total Fair Value	27,864	31,640
Certificates of Deposit [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	7,525	21,574
Certificates of Deposit [Member]
Total Fair Value	7,525	21,574
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	7,581
Corporate Debt Securities [Member]
Total Fair Value	7,581
US Government Agencies Short-term Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Total Fair Value	146,712	123,532
US Government Agencies Short-term Debt Securities [Member]
Total Fair Value	146,712	123,532
Auction Rate Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Total Fair Value	5,294	5,361
Auction Rate Securities [Member]
Total Fair Value	5,294	5,361
Mutual Fund [Member] | Fair Value, Inputs, Level 1 [Member]
Total Fair Value	10,162	8,279
Mutual Fund [Member]
Total Fair Value	10,162	8,279
Fair Value, Inputs, Level 1 [Member]
Total Fair Value	38,026	39,919
Fair Value, Inputs, Level 2 [Member]
Total Fair Value	161,818	145,106
Fair Value, Inputs, Level 3 [Member]
Total Fair Value	5,294	5,361
Total Fair Value	194,976	182,107
Total Fair Value	$ 205,138	$ 190,386