Note 7 - Property, Plant and Equipment and Construction-in-Process (Details) - Property, Plant and Equipment, Net (USD $)	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 2,126,553,000us-gaap_PropertyPlantAndEquipmentGross	$ 2,053,401,000us-gaap_PropertyPlantAndEquipmentGross
Less accumulated depreciation	(688,916,000)	(601,065,000)
Property, plant and equipment, net	1,437,637,000us-gaap_PropertyPlantAndEquipmentNet	1,452,336,000us-gaap_PropertyPlantAndEquipmentNet
Asset retirement cost	7,444,000	7,803,000
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	31,465,000	30,336,000
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	3,420,000	3,386,000
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	123,807,000	101,104,000
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	17,150,000	17,492,000
Automobiles [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	6,495,000	5,745,000
Geothermal and Recovered Energy Generation Power Plants [Member] \| UNITED STATES
Property, Plant and Equipment [Line Items]
Property, plant and equipment	1,463,291,000	1,439,374,000
Geothermal and Recovered Energy Generation Power Plants [Member] \| Foreign Countries [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 473,481,000	$ 448,161,000

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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-Name Accounting Standards Codification

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- Definition

The amount of asset retirement costs previously incurred and capitalized separately from the capitalized amount of the associated long-lived assets.

+ References

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-Name Accounting Standards Codification

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

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