Note 3 - Cash, Cash Equivalents and Investments - Cash Equivalents, Short-term and Long-term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash	$ 87,747	$ 58,217
Money market funds	24,956	31,640
Certificates of deposit		21,574
U.S. treasuries and government agency bonds	45,877	123,532
Total	273,578	240,324
Cash and cash equivalents	112,703	90,860	$ 126,266	$ 101,213
Short-term investments	155,521	144,103
Long-term investments	5,354	5,361
Corporate Debt Securities [Member]
Available-for-sale securities	109,644
Auction Rate Securities [Member]
Available-for-sale securities	$ 5,354	$ 5,361