v3.19.2

Note 2 - Investments and Fair Value Measurement - Fair Value of Financial Assets and Liabilities by Level Within Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Assets, fair value	$ 88,528	$ 103,678
Liabilities, fair value	657	121
Contingent Put Option Liability [Member]
Liabilities, fair value	657	121
Fair Value, Inputs, Level 1 [Member]
Assets, fair value	286	1,436
Liabilities, fair value
Fair Value, Inputs, Level 1 [Member] | Contingent Put Option Liability [Member]
Liabilities, fair value
Fair Value, Inputs, Level 2 [Member]
Assets, fair value	88,242	102,242
Liabilities, fair value
Fair Value, Inputs, Level 2 [Member] | Contingent Put Option Liability [Member]
Liabilities, fair value
Fair Value, Inputs, Level 3 [Member]
Assets, fair value
Liabilities, fair value	657	121
Fair Value, Inputs, Level 3 [Member] | Contingent Put Option Liability [Member]
Liabilities, fair value	657	121
Money Market Funds [Member]
Assets, fair value	286	1,436
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, fair value	286	1,436
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, fair value
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, fair value
Commercial Paper [Member]
Assets, fair value	88,242	90,564
Commercial Paper [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, fair value
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, fair value	88,242	90,564
Commercial Paper [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, fair value
U.S. Government Agency Obligations [Member]
Assets, fair value		11,678
U.S. Government Agency Obligations [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, fair value
U.S. Government Agency Obligations [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, fair value		11,678
U.S. Government Agency Obligations [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, fair value

X

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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X

- Definition

Fair value of financial and nonfinancial obligations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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