Note 8 - Unrealized Gains and Losses on Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Money Market Funds [Member]
Adjusted Cost	$ 27,864	$ 31,640
Total Fair Value	27,864	31,640
Certificates of Deposit [Member]
Adjusted Cost	7,525	21,574
Total Fair Value	7,525	21,574
Corporate Debt Securities [Member]
Adjusted Cost	7,570
Total Fair Value	7,581
Unrealized Gains	11
US Government Agencies Short-term Debt Securities [Member]
Adjusted Cost	146,619	123,698
Total Fair Value	146,712	123,532
Unrealized Gains	97	4
Unrealized Losses	(4)	(170)
Fair Value of Investments in Unrealized Loss Position	16,002	110,720
Auction Rate Securities [Member]
Adjusted Cost	5,570	5,570
Total Fair Value	5,294	5,361
Unrealized Losses	(276)	(209)
Fair Value of Investments in Unrealized Loss Position	5,294	5,361
Adjusted Cost	195,148	182,482
Total Fair Value	194,976	182,107
Unrealized Gains	108	4
Unrealized Losses	(280)	(379)
Fair Value of Investments in Unrealized Loss Position	$ 21,296	$ 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
-SubTopic 10
-Section 25
-Paragraph 1
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-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 2
-Subparagraph (b)
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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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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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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