Note 13 - Discontinued Operations (Details) - Summary of Financial Information Related to Discontinued Operations (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues - electricity	$ 87,713	$ 81,882	$ 156,011	$ 161,225
Income from discontinued operations, net of taxes	4,480	1,613	5,311	2,693
Momotombo Power Plant [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues - electricity	2,062	3,129	4,866	6,033
Income from discontinued operations before income taxes	4,480	1,613	5,311	2,693
Income tax provision	(363)	(425)	(614)	(706)
Income from discontinued operations, net of taxes	$ 4,117	$ 1,188	$ 4,697	$ 1,987

Overall income (loss) from a disposal group that is classified as a component of the entity, before income tax, reported as a separate component of income before extraordinary items. Includes the following (before income tax): income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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Tax effect allocated to a disposal group that is classified as a component of the entity reported as a separate component of income before extraordinary items. Includes the tax effects of the following: income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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