Note 8 - Cash, Cash Equivalents and Investments - Unrealized Gains and Losses on Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Adjusted Cost	$ 216,252	$ 186,854
Total Fair Value	215,431	185,831
Unrealized Gains	78	65
Unrealized Losses	(899)	(1,088)
Fair Value of Investments in Unrealized Loss Position	155,528	136,567
Money Market Funds [Member]
Adjusted Cost	8,274	24,956
Total Fair Value	8,274	24,956
Certificates of Deposit [Member]
Adjusted Cost	7,256
Total Fair Value	7,256
Corporate Debt Securities [Member]
Adjusted Cost	170,959	110,429
Total Fair Value	170,389	109,644
Unrealized Gains	75	65
Unrealized Losses	(645)	(850)
Fair Value of Investments in Unrealized Loss Position	129,006	91,938
US Government Agencies Short-term Debt Securities [Member]
Adjusted Cost	24,193	45,899
Total Fair Value	24,170	45,877
Unrealized Gains	3
Unrealized Losses	(26)	(22)
Fair Value of Investments in Unrealized Loss Position	21,180	39,275
Auction Rate Securities [Member]
Adjusted Cost	5,570	5,570
Total Fair Value	5,342	5,354
Unrealized Losses	(228)	(216)
Fair Value of Investments in Unrealized Loss Position	$ 5,342	$ 5,354

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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