Note 7 - Property, Plant and Equipment and Construction-In-Process (Details) - Property, Plant and Equipment, Net (USD $)	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property, plant and equipment gross	$ 2,053,401,000		$ 1,797,543,000
Less accumulated depreciation	(601,065,000)		(544,670,000)
Property, plant and equipment, net	1,452,336,000	1,233,525,000	1,252,873,000
Asset retirement cost	7,803,000		7,214,000
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment gross	30,336,000		32,396,000
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment gross	3,386,000		1,339,000
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment gross	101,104,000		100,499,000
Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment gross	17,492,000		15,218,000
Automobiles [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment gross	5,745,000		5,816,000
Geothermal and Recovered Energy Generation Power Plants [Member] | UNITED STATES
Property, Plant and Equipment [Line Items]
Property, plant and equipment gross	1,439,374,000		1,322,649,000
Geothermal and Recovered Energy Generation Power Plants [Member] | Foreign Countries [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment gross	$ 448,161,000		$ 312,412,000