Note 8 - Unrealized Gains and Losses on Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Money Market Funds [Member]
Adjusted Cost	$ 47,261	$ 31,640
Total Fair Value	47,261	31,640
Certificates of Deposit [Member]
Adjusted Cost	7,495	21,574
Total Fair Value	7,495	21,574
Corporate Debt Securities [Member]
Adjusted Cost	20,703
Total Fair Value	20,665
Unrealized Gains	4
Unrealized Losses	(42)
Fair Value of Investments in Unrealized Loss Position	17,894
US Government Agencies Short-term Debt Securities [Member]
Adjusted Cost	121,383	123,698
Total Fair Value	121,424	123,532
Unrealized Gains	48	4
Unrealized Losses	(7)	(170)
Fair Value of Investments in Unrealized Loss Position	26,037	110,720
Auction Rate Securities [Member]
Adjusted Cost	5,570	5,570
Total Fair Value	5,382	5,361
Unrealized Losses	(188)	(209)
Fair Value of Investments in Unrealized Loss Position	5,382	5,361
Adjusted Cost	202,412	182,482
Total Fair Value	202,227	182,107
Unrealized Gains	52	4
Unrealized Losses	(237)	(379)
Fair Value of Investments in Unrealized Loss Position	$ 49,313	$ 116,081

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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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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-Publisher FASB
-Name Accounting Standards Codification
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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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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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