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Note 7 - Derivative Instruments and Hedging Activities (Details Textual) - Foreign Exchange Forward [Member] $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 CAD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2017 CAD ($)
Unrealized Gain on Foreign Currency Derivatives, before Tax			$ 0
Maximum [Member]
Maturity Period For Forward Contracts			1 year
Designated as Hedging Instrument [Member]
Derivative, Notional Amount	$ 2,000,000		$ 2,000,000		$ 2.6	$ 2,100,000	$ 2.7
Not Designated as Hedging Instrument [Member]
Derivative, Notional Amount						$ 200,000	$ 0.2
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net, Total	$ 0	$ 0	$ 100,000	$ 0

X

- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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X

- Definition

The period of maturity for forward contracts.

+ References

No definition available.

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X

- Definition

Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4CC
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109998890-113959

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

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- Definition

Amount of unrealized gain related to the increase in fair value of foreign currency exchange rate derivatives designated as cash flow hedging instruments. Recorded in accumulated other comprehensive income to the extent that the cash flow hedge is determined to be effective.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

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