Note 8 - Share-based Compensation - Restricted Stock Unit Activity (Details) - Restricted Stock Units (RSUs) [Member]	3 Months Ended
Mar. 31, 2019 $ / shares shares
Unvested (in shares) \| shares	1,401,674
Unvested, weighted average (in dollars per share) \| $ / shares	$ 2
Vested (in shares) \| shares	173,320
Vested, weighted average (in dollars per share) \| $ / shares	$ 2.15
Unvested (in shares) \| shares	1,228,354
Unvested, weighted average (in dollars per share) \| $ / shares	$ 1.98

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

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-Section 50
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