Consolidated Statement of Stockholders' Equity (Deficit) (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
The September 2019 Offering [Member]
Offering costs from issuance of common stock and warrants		$ 1,579
The April 2019 Offering [Member]
Offering costs from issuance of common stock and warrants		1,459
The March 2020 Offering [Member]
Offering costs from issuance of common stock and warrants	$ 1,278
The July 2020 Offering [Member]
Offering costs	2,966
The December 2020 Offering [Member]
Offering costs	$ 563
Offering costs		$ 560

Amount of decrease in additional paid in capital (APIC) resulting from direct costs associated with issuing stock. Includes, but is not limited to, legal and accounting fees and direct costs associated with stock issues under a shelf registration.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

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