Note 7 - Concentration of Revenue - Concentration of Revenue (Details) - Customer Concentration Risk [Member] - Sales Revenue, Net [Member]	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Customer A [Member]
Concentration risk	11.10%	11.60%
Customer B [Member]
Concentration risk	5.50%	13.60%
Customer C [Member]
Concentration risk	7.50%	15.20%
Customer D [Member]
Concentration risk	20.30%	14.50%
Customer E [Member]
Concentration risk	27.30%

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
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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