Note 2 - Basis of Presentation and Recent Accounting Pronouncements (Details Textual) - USD ($)	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Cash Equivalents, at Carrying Value, Total	$ 15,023,000		$ 0
Impairment of Long-Lived Assets Held-for-use	$ 0	$ 0

The aggregate amount of write-downs for impairments recognized during the period for long lived assets held for use (including those held for disposal by means other than sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 958
-SubTopic 220
-Section 45
-Paragraph 11
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-URI http://asc.fasb.org/extlink&oid=114873921&loc=SL114875236-224282

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
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