Note 3 - Revenue (Details Textual) $ in Thousands	6 Months Ended
Jun. 30, 2018 USD ($)
Accounting Standards Update 2014-09 [Member]
Cumulative Effect on Retained Earnings, Net of Tax, Total	$ 0

Amount of the cumulative effect on retained earnings net of related income tax effect.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22663-107794

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