Note 12 - Segment Reporting - Revenue From Operations by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue	$ 117,455	$ 115,430	$ 346,839	$ 332,827
Operating Segments [Member]
Revenue	117,455	115,430	346,839	332,827
Operating Segments [Member] \| United States Segment [Member]
Revenue	92,916	90,732	271,877	261,253
Operating Segments [Member] \| Europe Segment [Member]
Revenue	20,721	21,273	62,915	61,431
Operating Segments [Member] \| Japan Segment [Member]
Revenue	$ 3,818	$ 3,425	$ 12,047	$ 10,143

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration