Note 7 - Fair Value Measurements - Reconciliation of Level 3 Activity (Details) - Warrant Liabilities [Member] - Fair Value, Inputs, Level 3 [Member] $ in Thousands	9 Months Ended
Sep. 30, 2019 USD ($)
Balance	$ 865
Reclassification of warrant liability to additional paid-in capital upon adoption of ASU 2017-11	(865)
Balance

Amount of increase (decrease) of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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 (c)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration