Note 8 - Segments - Sales by Geographic Region (Details) - Sales Revenue, Segment [Member] - Geographic Concentration Risk [Member]	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
UNITED STATES
Percentage of sales	62.00%	58.00%	61.00%	59.00%
Europe [Member]
Percentage of sales	17.00%	21.00%	18.00%	21.00%
Other [Member]
Percentage of sales	21.00%	21.00%	21.00%	20.00%

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
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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