Note 5 - Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Money Market Funds [Member] \| Fair Value, Inputs, Level 2 [Member]
Cash equivalents	$ 67,001	$ 61,385
Money Market Funds [Member]
Cash equivalents	67,001	61,385
Certificates of Deposit [Member] \| Fair Value, Inputs, Level 2 [Member]
Cash equivalents		250
Investments	22,500	25,750
Certificates of Deposit [Member]
Cash equivalents		250
Investments	22,500	25,750
Corporate Debt Securities [Member]
Investments		2,001
Fair Value, Inputs, Level 2 [Member]
Cash equivalents		61,635
Cash equivalents		61,635
Investments	$ 22,500	$ 27,751

Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26626-111562

Reference 3: 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)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant