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, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized	$ (2,600)	$ (2,577)
Electricity Revenues [Member] | Crude Oil Price Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized	907	(295)
Electricity Revenues [Member] | Natural Gas Price Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized	(3,276)	(3,390)
Electricity Revenues [Member] | Put Option [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized		(927)
Foreign Currency Gain (Loss) [Member] | Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized	$ (231)	$ 2,035