Note 5 - Fair Value of Financial Instruments (Details) - Amounts of Gain (Loss) Recognized in Condensed Consolidated Statements on Derivative Instruments not Designated as Hedges - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized	$ 1,238	$ 1,530	$ (582)	$ (1,154)
Electricity Revenues [Member] | Crude Oil Price Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized		1,657		1,885
Electricity Revenues [Member] | Natural Gas Price Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized	369	2,295	767	(609)
Foreign Currency Gain (Loss) [Member] | Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized	$ 869	$ (2,422)	$ (1,349)	$ (2,430)