Note 12 - Segment Reporting - Revenue From Operations by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue:
Revenue	$ 115,932	$ 109,652	$ 229,384	$ 217,397
Operating Segments [Member]
Revenue:
Revenue	115,932	109,652	229,384	217,397
Operating Segments [Member] \| United States Segment [Member]
Revenue:
Revenue	91,149	86,354	178,960	170,521
Operating Segments [Member] \| Europe Segment [Member]
Revenue:
Revenue	20,940	20,213	42,194	40,158
Operating Segments [Member] \| Japan Segment [Member]
Revenue:
Revenue	$ 3,843	$ 3,085	$ 8,230	$ 6,718

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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration