Note 1 - Business and Significant Accounting Policies (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011	Dec. 31, 2010
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Valuation Allowances and Reserves, Adjustments	$ 3,100,000				$ 32,700,000
Dividends, Common Stock, Cash			3,636,000		3,636,000		5,924,000
Common Stock, Dividends, Per Share, Declared (in Dollars per share)			$ 0.08				$ 0.13
Cash, Cash Equivalents, and Short-term Investments		57,354,000	57,354,000	66,628,000	66,628,000	99,886,000	99,886,000	82,815,000
Accounts Receivable, Net, Current		95,365,000	95,365,000
Percentage of Total Accounts Receivables		35.00%	35.00%	45.00%	45.00%
Interest Costs Capitalized			7,598,000		11,964,000		11,709,000
Grants Received From United States Government To Offset Costs Incurred Related To Exploration And Development Costs			1,665,000		1,368,000		6,194,000
Accumulated Amortization, Deferred Finance Costs		25,371,000	25,371,000	20,209,000	20,209,000
Amortization of Financing Costs		6,009,000		3,676,000		3,567,000
Deferred Costs, Leasing, Gross		4,200,000	4,200,000
LeasePaymentTerm			23 years		23 years
Other Comprehensive Income (Loss), Net of Tax			(164,000)		56,000		(449,000)
Other Comprehensive Income (Loss), before Tax			265,000		61,000		579,000
Other Comprehensive Income (Loss), Tax			101,000		117,000		130,000
Research and Development Arrangement with Federal Government, Customer Funding to Offset Costs Incurred			1,616,000		660,000		1,143,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in Shares)			5,139,339		5,479,852		4,337,475
Southern California Edison Company [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Termination Fees		9,000,000	9,000,000
NV Energy [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Termination Fees		2,600,000	2,600,000
Power Plants [Member] | Minimum [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Property, Plant and Equipment, Useful Life			25 years
Power Plants [Member] | Maximum [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Property, Plant and Equipment, Useful Life			30 years
Domestic Tax Authority [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Cash, Cash Equivalents, and Short-term Investments		13,805,000	13,805,000	41,231,000	41,231,000
Deposit Insurance Per Depositor (in Dollars per Item)		250,000	250,000
Foreign Tax Authority [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Cash, Cash Equivalents, and Short-term Investments		56,133,000	56,133,000	33,215,000	33,215,000
Accounts Receivable, Net, Current		32,231,000	32,231,000	17,606,000	17,606,000
Reclassification out of Accumulated Other Comprehensive Income [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Dividends, Common Stock, Cash							5,900,000
Common Stock, Dividends, Per Share, Declared (in Dollars per share)					$ 0.08		$ 0.13
Puna Geothermal Ventures [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Deferred Costs, Leasing, Gross		4,172,000	4,172,000
LeasePaymentTerm			23 years
Deferred Costs, Leasing, Accumulated Amortization		1,589,000	1,589,000	1,405,000	1,405,000
Amortization of Deferred Leasing Fees			184,000
Written-Off as a Result of Extinguishment of Debt [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Amortization of Financing Costs			254,000
Deferred Income Tax Charge [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Valuation Allowances and Reserves, Adjustments	3,100,000				6,600,000
Property, Plant and Equipment [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Valuation Allowances and Reserves, Adjustments					$ 26,100,000
Minimum [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Finite-Lived Intangible Asset, Useful Life			13 years
Maximum [Member]
Note 1 - Business and Significant Accounting Policies (Details) [Line Items]
Finite-Lived Intangible Asset, Useful Life			25 years