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		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized	$ 1,530	$ 1,623	$ (1,154)	$ 3,426
Electricity Revenues [Member] | Put Option [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized		(824)		(1,256)
Electricity Revenues [Member] | Crude Oil Price Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized	1,657		1,885	(294)
Electricity Revenues [Member] | Natural Gas Price Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized	2,295	477	(609)	81
Foreign Currency Gain (Loss) [Member] | Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized	$ (2,422)	$ 1,970	$ (2,430)	$ 4,895