Note 2 - Summary of Significant Accounting Policies - Concentrations (Details) - customer	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Revenue Benchmark
Concentrations
Number of Major Customers	2	3
Accounts Receivable.
Concentrations
Number of Major Customers	2
Customer Concentration Risk \| Revenue Benchmark
Concentrations
Concentration Risk, Percentage	66.00%
Customer Concentration Risk \| Revenue Benchmark \| Customer A
Concentrations
Concentration Risk, Percentage	35.00%
Customer Concentration Risk \| Revenue Benchmark \| Customer B
Concentrations
Concentration Risk, Percentage	31.00%
Customer Concentration Risk \| Accounts Receivable.
Concentrations
Concentration Risk, Percentage	65.00%	73.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13531-108611

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13537-108611

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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