Note 1 - General and Basis of Presentation (Details) (USD $)	3 Months Ended		6 Months Ended	9 Months Ended				0 Months Ended	3 Months Ended			3 Months Ended		6 Months Ended	9 Months Ended		0 Months Ended	9 Months Ended	0 Months Ended	9 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		0 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Mar. 26, 2014 Heber Solar Project [Member]	Jun. 30, 2014 Heber Solar Project [Member]	Mar. 31, 2014 Heber Solar Project [Member]	Mar. 31, 2013 Selling and Marketing Expense [Member] Southern California Edison Company [Member]	Sep. 30, 2014 Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member]	Jun. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2014 Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member]	Aug. 05, 2014 Noncontrolling Interest [Member] Crump Geyser Company [Member]	Sep. 30, 2014 Noncontrolling Interest [Member]	Aug. 05, 2014 Additional Paid-in Capital [Member] Crump Geyser Company [Member]	Sep. 30, 2014 Additional Paid-in Capital [Member]	Sep. 30, 2014 Southern California Edison Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2013 Southern California Edison Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2014 Southern California Edison Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2013 Southern California Edison Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Mar. 31, 2013 Southern California Edison Company [Member]	Sep. 30, 2014 Primary Customers [Member] Accounts Receivable [Member] Customer Concentration Risk [Member]	Dec. 31, 2013 Primary Customers [Member] Accounts Receivable [Member] Customer Concentration Risk [Member]	Sep. 30, 2014 Sierra Pacific Power Company And Nevada Power Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2013 Sierra Pacific Power Company And Nevada Power Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2014 Sierra Pacific Power Company And Nevada Power Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2013 Sierra Pacific Power Company And Nevada Power Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2014 Hawaii Electric Light Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2013 Hawaii Electric Light Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2014 Hawaii Electric Light Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2013 Hawaii Electric Light Company [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2014 Kenya Power And Lighting Co Limited [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2013 Kenya Power And Lighting Co Limited [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2014 Kenya Power And Lighting Co Limited [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Sep. 30, 2013 Kenya Power And Lighting Co Limited [Member] Sales Revenue, Net [Member] Customer Concentration Risk [Member]	Aug. 05, 2014 Crump Geyser Company [Member]	Sep. 30, 2014 Maximum [Member]	Dec. 31, 2013 Maximum [Member]	Sep. 30, 2014 UNITED STATES	Dec. 31, 2013 UNITED STATES	Sep. 30, 2014 Foreign Countries [Member]	Dec. 31, 2013 Foreign Countries [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 35,000	$ 40,000	$ 107,000		$ 124,000
Interest Expense	22,494,000	18,459,000		65,084,000	51,826,000							57,000	76,000		173,000	200,000
Income Tax Expense (Benefit)	6,444,000	5,201,000		17,731,000	15,028,000							22,000	25,000	88,000	66,000
Termination Fees											9,000,000
Contract Extension Period																									6 years
Sales Price of Disposition								35,250,000
Proceeds from Sales of Business, Affiliate and Productive Assets									20,250,000	15,000,000
Gain (Loss) on Sale of Project									7,600,000
Exploration Abandonment and Impairment Expense	8,100,000			8,107,000
Payments to Acquire Interest in Subsidiaries and Affiliates				1,490,000																																				1,500,000
Noncontrolling Interest, Ownership Percentage by Parent																																								50.00%
Noncontrolling Interest, Increase from Business Combination				(828,000)													(1,000,000)	(987,000)	200,000	159,000
Cash, FDIC Insured Amount																																									250,000	250,000
Cash, Cash Equivalents, and Short-term Investments	42,451,000	35,435,000		42,451,000	35,435,000	57,354,000	66,628,000																																				23,016,000	13,805,000	31,279,000	56,133,000
Accounts Receivable, Net, Current	75,224,000			75,224,000		95,365,000																																							42,914,000	32,231,000
Concentration Risk, Percentage																					19.80%	20.90%	15.20%	14.90%		54.10%	35.00%	14.60%	15.30%	16.60%	17.00%	7.30%	8.70%	8.80%	8.90%	15.70%	13.90%	15.60%	10.90%
Provision for Doubtful Accounts				$ 0