v3.8.0.1

Note 2 - Investments and Fair Value Measurement - Summary of Cash, Cash Equivalents and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Amortized Cost	$ 60,469	$ 80,307
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	60,469	80,310
Cash and cash equivalents:
Amortized Cost	60,469	80,307
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	60,469	80,310
Cash and Cash Equivalents [Member]
Amortized Cost	52,902	80,307
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	52,902	80,310
Cash and cash equivalents:
Amortized Cost	52,902	80,307
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	52,902	80,310
Cash and Cash Equivalents [Member] | Cash [Member]
Amortized Cost	29,765	49,833
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	29,765	49,833
Cash and cash equivalents:
Amortized Cost	29,765	49,833
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	29,765	49,833
Cash and Cash Equivalents [Member] | U.S. Government Agency Securities [Member]
Amortized Cost	23,137	30,474
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	23,137	30,477
Cash and cash equivalents:
Amortized Cost	23,137	30,474
Gross Unrealized Gains		3
Gross Unrealized Losses
Fair Value	23,137	$ 30,477
Marketable Securities [Member]
Amortized Cost	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	7,567
Cash and cash equivalents:
Amortized Cost	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	7,567
Marketable Securities [Member] | U.S. Government Agency Securities [Member]
Amortized Cost	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	7,567
Cash and cash equivalents:
Amortized Cost	7,567
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	$ 7,567

X

- Definition

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

+ References

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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X

- Definition

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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X

- Definition

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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X

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ 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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- References

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