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Note 11 - Derivative Instruments and Hedging Activities (Details Textual) $ in Millions | 12 Months Ended |  |
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Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2017 CAD ($) | Dec. 31, 2016 CAD ($)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net | $ 0 | $ 0 | $ 400,000 |  |
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months | 0 |  |  |  |
Canadian Forward Contract, Remaining Maturities of 15 to 17 Months [Member] |  |  |  |  |
Derivative, Notional Amount | $ 2,100,000 |  |  | $ 2.7 |
Derivative, Number of Instruments Held | 2 |  |  | 2 |
Maximum [Member] |  |  |  |  |
Maturity Period For Forward Contracts | 1 year |  |  |  |
Designated as Hedging Instrument [Member] |  |  |  |  |
Derivative, Notional Amount | $ 2,100,000 | 3,400,000 |  | $ 2.7 | $ 4.5
Not Designated as Hedging Instrument [Member] |  |  |  |  |
Derivative, Notional Amount | $ 200,000 | $ 900,000 |  | $ 0.2 | $ 1.3

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- 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 + Details
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- Definition The period of maturity for forward contracts. + References No definition available. + Details
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- 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/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959 + Details
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- Definition The number of derivative instruments of a particular group held by the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959 + Details
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- Definition The estimated net amount of unrealized gains or losses on foreign currency cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80748-113994 + Details
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