Note 3 - Revenue From Contracts With Customers (Details Textual) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Number of Categories in Product Offerings	2
Contract with Customer, Liability, Revenue Recognized	$ 0.9
Transferred at Point in Time [Member]
Percentage of Revenue From Goods and Services	82.00%

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

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