Note 5 - Derivative Instruments and Hedging Activities (Details Textual) CAD in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 CAD	Sep. 30, 2016 USD ($)	Dec. 31, 2015 CAD	Dec. 31, 2015 USD ($)
Designated as Hedging Instrument [Member]
Derivative, Notional Amount					CAD 6.1	$ 4,700,000	CAD 8.7	$ 6,300,000
Maximum [Member]
Maturity Period For Forward Contracts			1 year
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 76,000	$ 200,000	$ (133,000)	$ 200,000
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months		$ 18,000		$ 18,000		$ (20,000)