Note 6 - Deferred Revenue (Details Textual) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Revenue, Remaining Performance Obligation, Percentage	78.00%
Revenue, Remaining Performance Obligation, Amount	$ 12.9
Deferred Revenue Costs Incurred	$ 2.2	$ 2.0

Percentage of remaining performance obligation to total remaining performance obligation not recognized as revenue.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

Name:	us-gaap_RevenueRemainingPerformanceObligationPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant