Note 5 - Derivative Instruments and Hedging Activities (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Derivative, Notional Amount	$ 12,779,952
Foreign Exchange Forward [Member]
Derivative, Notional Amount	12,800,000		$ 0
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	3,093	$ 34,425
Foreign Exchange Forward [Member] \| Designated as Hedging Instrument [Member]
Derivative, Notional Amount	$ 11,300,000

Amount of gain (loss) recognized in earnings in the period from the increase (decrease) in fair value of foreign currency derivatives not designated as hedging instruments.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

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