Note 6 - Segment Reporting (Details Textual)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Reportable Segments	2
Geographic Concentration Risk [Member] \| Sales Revenue, Net [Member] \| UNITED STATES
Concentration Risk, Percentage	74.00%	74.00%	77.00%
Geographic Concentration Risk [Member] \| Net Assets, Geographic Area [Member] \| UNITED STATES
Concentration Risk, Percentage	80.00%	85.00%
Term Loan [Member]
Debt Instrument, Interest Rate, Increase (Decrease)			0.25%
Net Debt Leverage Ratio Not Achieved			3

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
-Topic 825
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

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