Note 1 - General - Cash, Cash Equivalents and Short-term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Member]
Amortized cost	$ 53,478	$ 48,315
Gross unrealized gains
Gross unrealized losses
Fair value	53,478	48,315
Cash and Cash Equivalents [Member] \| Cash [Member]
Amortized cost	46,796	42,175
Gross unrealized gains
Gross unrealized losses
Fair value	46,796	42,175
Cash and Cash Equivalents [Member] \| Money Market Funds [Member]
Amortized cost	6,682	6,140
Gross unrealized gains
Gross unrealized losses
Fair value	6,682	6,140
Cash and Cash Equivalents [Member] \| US Treasury Securities Included in Cash and Cash Equivalents [Member]
Amortized cost	39,830
Gross unrealized gains	2
Gross unrealized losses	(5)
Fair value	39,827
Short-term Investments [Member]
Amortized cost	74,966	65,493
Gross unrealized gains	2
Gross unrealized losses	(5)
Fair value	74,963	65,493
Short-term Investments [Member] \| Term Bank Deposits [Member]
Amortized cost	35,136	65,493
Gross unrealized gains
Gross unrealized losses
Fair value	$ 35,136	$ 65,493

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
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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

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