Note 12 - Long-term Debt, Credit Agreements and Finance Liability (Details Textual) $ in Thousands, ₪ in Billions															1 Months Ended		12 Months Ended
		Sep. 02, 2021 USD ($)	Jul. 15, 2021 USD ($)	Jul. 12, 2021 USD ($)	Jul. 20, 2020 USD ($)	Apr. 06, 2020 USD ($)	Jul. 03, 2019 USD ($)	May 30, 2019	Apr. 09, 2019 USD ($)	Mar. 25, 2019 USD ($)	Mar. 22, 2018 USD ($)	Dec. 21, 2016 USD ($)	Jul. 31, 2015 USD ($) MWh	Feb. 29, 2012	Oct. 31, 2018 MWh	May 31, 2013	Dec. 31, 2021 USD ($)		Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jul. 13, 2021 USD ($)	Jul. 01, 2020 USD ($)	Jul. 01, 2020 ILS (₪)	May 13, 2020 USD ($)	Apr. 30, 2020 USD ($)	Apr. 20, 2020 USD ($)	May 04, 2019 USD ($)	Apr. 29, 2019	Apr. 04, 2019 USD ($)	Jan. 04, 2019 USD ($)	Dec. 31, 2018 USD ($)	Apr. 30, 2018 USD ($)	May 31, 2017 USD ($)	Nov. 29, 2016 USD ($)	Oct. 20, 2016 USD ($)	Sep. 30, 2016 USD ($)	May 31, 2016 USD ($)	Aug. 29, 2014 USD ($)	Aug. 23, 2012 USD ($)	Oct. 31, 2011 USD ($)	Sep. 30, 2011 USD ($)	Aug. 31, 2011 USD ($)
Letters of Credit Outstanding, Amount																	$ 185,000
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																	4.02
Proceeds from Issuance of Commercial Paper							$ 50,000										$ 0		$ 0	$ 50,000
Stockholders' Equity Attributable to Parent, Ending Balance																	$ 1,854,999		1,805,985
Percentage Of Company Assets																	45.20%
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance																	$ 1,998,461		1,941,437	1,515,410											$ 1,445,038
Payments of Dividends, Total																	$ 27,000		$ 22,500	$ 22,400
Covenant Requirement Minimum [Member]
Amount Available For Dividend Distribution Percent Of Cumulative Net Income																	50
Stockholders' Equity Attributable to Parent, Ending Balance																	$ 750,000
Percentage Of Company Assets																	25.00%
London Interbank Offered Rate (LIBOR) [Member] | Commercial Paper [Member]
Debt Instrument, Basis Spread on Variable Rate							0.75%
Maximum [Member] | Covenant Requirement Minimum [Member]
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																	6
Maximum [Member] | Commercial Paper [Member]
Debt Instrument, Term (Year)							5 years
Minimum [Member] | Commercial Paper [Member]
Debt Instrument, Term (Year)							90 days
Pomona Energy Storage [Member]
Business Combination, Consideration Transferred, Total					$ 43,400
Two Contracted Geothermal Assets in Nevada [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finance Lease Liability	[1]																				$ 258,400
Hapoalim Loan Agreement [Member] | Bank Hapoalim B.M. [Member]
Debt Instrument, Face Amount				$ 125,000
Debt Instrument, Number of Semi-annual Payments				14
Debt Instrument, Periodic Payment, Total				$ 8,900
Debt Instrument, Term (Year)				7 years
Debt Instrument, Interest Rate, Stated Percentage				3.45%
Debt Instrument, Covenant, Maximum Debt to EBITDA Ratio				6
Debt Instrument, Covenant, Minimum Equity Capital, Amount				$ 750,000
Debt Instrument, Covenant, Equity Capital to Total Assets, Percent				25
HSBC Loan Agreement [Member] | HSBC Bank PLC [Member]
Debt Instrument, Face Amount			$ 50,000
Debt Instrument, Number of Semi-annual Payments			14
Debt Instrument, Periodic Payment, Total			$ 3,600
Debt Instrument, Term (Year)			7 years
Debt Instrument, Interest Rate, Stated Percentage			3.45%
Debt Instrument, Covenant, Maximum Debt to EBITDA Ratio			6
Debt Instrument, Covenant, Minimum Equity Capital, Amount			$ 750,000
Debt Instrument, Covenant, Equity Capital to Total Assets, Percent			25
Discount Loan Agreement [Member]
Debt Instrument, Face Amount																	$ 100,000
Debt Instrument, Interest Rate, Stated Percentage	[2]																2.90%
Long-term Debt, Gross																	$ 100,000
Discount Loan Agreement [Member] | Israel Discount Bank Ltd. [Member]
Debt Instrument, Face Amount		$ 100,000
Debt Instrument, Number of Semi-annual Payments		16
Debt Instrument, Periodic Payment, Total		$ 6,250
Debt Instrument, Term (Year)		8 years
Debt Instrument, Interest Rate, Stated Percentage		2.90%
Debt Instrument, Covenant, Maximum Debt to EBITDA Ratio		6
Debt Instrument, Covenant, Minimum Equity Capital, Amount		$ 750,000
Debt Instrument, Covenant, Equity Capital to Total Assets, Percent		25
Senior Unsecured Bonds, Series 4 [Member]
Debt Instrument, Face Amount																	$ 289,800					$ 289,800	₪ 1
Debt Instrument, Interest Rate, Stated Percentage	[2]																3.35%
Debt Instrument, Number of Annual Payments																						10	10
Long-term Debt, Gross																	$ 321,500
Senior Unsecured Bonds, Series 4 [Member] | Cross Currency Interest Rate Contract [Member]
Derivative, Fixed Interest Rate																						4.34%	4.34%
Senior Unsecured Bonds, Series 2 [Member]
Debt Instrument, Face Amount																																				$ 67,000
Senior Unsecured Bonds, Series 3 [Member]
Debt Instrument, Face Amount						$ 51,100											$ 218,000							$ 15,300		$ 14,500										$ 137,000
Debt Instrument, Interest Rate, Stated Percentage						4.45%											4.45%	[2]
Proceeds from Issuance of Long-term Debt, Total						$ 50,000
Long-term Debt, Gross																	$ 218,000
Senior Unsecured Loan (Migdal) [Member]
Debt Instrument, Face Amount											$ 100,000						$ 100,000
Debt Instrument, Periodic Payment, Total											4,200
Debt Instrument, Interest Rate, Stated Percentage	[3]																4.80%
Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid											$ 37,000
Debt Instrument Increase in Stated Interest Rate if Rating is Downgraded to ILA Negative											0.50%
Debt Instrument Increase in Stated Interest Rate Each Additional Downgrade											0.25%
Debt Instrument Decrease in Stated Interest Rate for Each Rating Upgrade											0.25%
Debt to EBITDA Ratio Threshold for Rate Increase											4.5
Debt Instrument Increase in Stated Interest Rate if Debt to EBITDA Ratio Exceeds Threshold											0.50%
Debt to EBITDA Ratio Requirement											6
Stockholders Equity, Debt Covenant, Minimum Threshold											$ 750,000
Stockholders Equity to Total Assets, Ratio											25.00%
Stockholders Equity, Debt Covenant, Minimum Threshold to Pay Dividends											$ 800,000
Dividends to Net Income, Ratio											50.00%
Long-term Debt, Gross																	$ 95,800
Senior Unsecured Loan (Migdal) [Member] | Maximum [Member]
Debt Instrument, Increase in Stated Interest Rate											1.00%
Senior Unsecured Loan (Migdal) [Member] | Minimum [Member]
Debt Instrument, Interest Rate, Stated Percentage											4.80%
Additional Migdal Loan [Member]
Debt Instrument, Face Amount										$ 50,000							$ 50,000
Debt Instrument, Number of Semi-annual Payments										15
Debt Instrument, Periodic Payment, Total										$ 2,100
Debt Instrument, Interest Rate, Stated Percentage	[3]																4.60%
Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid										$ 18,500
Long-term Debt, Gross																	$ 47,900
Second Addendum Migdal Loan [Member]
Debt Instrument, Face Amount																	$ 50,000								$ 50,000
Debt Instrument, Number of Semi-annual Payments																									15
Debt Instrument, Interest Rate, Stated Percentage	[3]																5.44%
Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid																									$ 18,500
Debt Instrument, Principal to Be Repaid in Installments																									$ 31,500
Long-term Debt, Gross																	$ 47,900
DEG 2 Facility Agreement [Member]
Debt Instrument, Interest Rate, Stated Percentage												6.28%
Line of Credit Facility, Maximum Borrowing Capacity																																			$ 50,000
Proceeds from Lines of Credit, Total												$ 50,000
DEG 3 Loan Agreement [Member]
Debt Instrument, Number of Semi-annual Payments																														19
Debt Instrument, Interest Rate, Stated Percentage																														6.04%
DEG 3 Loan Agreement [Member] | OrPower 4, Inc [Member]
Debt Instrument, Face Amount																														$ 41,500
Loan Agreement With OPIC the Olkaria III Power Plant [Member]
Debt Instrument, Face Amount																	310,000																						$ 310,000
Long-term Debt, Gross																	156,700
Platanares Finance Agreement [Member]
Debt Instrument, Face Amount																	$ 114,700
Debt Instrument, Interest Rate, Stated Percentage	[4]																7.02%
Long-term Debt, Gross																	$ 88,100
Platanares Finance Agreement [Member] | OPIC [Member]
Debt Instrument, Face Amount																																$ 114,700
Current Power Generation (Megawatt-Hour) | MWh															35
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited1 [Member]
Debt Instrument, Face Amount													$ 42,000				42,000
Debt Instrument, Term (Year)													12 years
Power Utilization (Megawatt-Hour) | MWh													20
Debt Instrument Number of Quarterly Payments													48
Long-term Debt, Gross																	$ 19,300
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited1 [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	[4]																4.35%
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited1 [Member] | London Interbank Offered Rate (LIBOR) [Member] | Guaranteed [Member]
Debt Instrument, Basis Spread on Variable Rate													4.35%
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited1 [Member] | London Interbank Offered Rate (LIBOR) [Member] | Not Guaranteed [Member]
Debt Instrument, Basis Spread on Variable Rate													4.75%
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited1 [Member] | Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate													1.25%
Plumstriker Loan Agreement [Member]
Debt Instrument, Face Amount																	$ 23,500
Long-term Debt, Gross																	$ 14,700
Plumstriker Loan Agreement [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	[4]																3.50%
Plumstriker Loan Agreement [Member] | Plumstriker and its Two Subsidiaries [Member]
Debt Instrument, Face Amount																											$ 23,500
Debt Instrument, Equal Quarterly Principal Installments, Percentage of Loan								1.25%
Plumstriker Loan Agreement [Member] | Plumstriker and its Two Subsidiaries [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate								3.50%
Don A. Cambell Senior Secured Notes [Member]
Debt Instrument, Face Amount																																		$ 92,500
OFC Two Senior Secured Notes [Member]
Debt Instrument, Face Amount																																								$ 151,700	$ 350,000
Government Guarantee Percent																																									80.00%
OFC Two Senior Secured Notes [Member] | Wholly Owned Subsidiaries With Project Debt [Member]
Debt Instrument, Face Amount																																						$ 140,000
Prudential Capital Group Agreement [Member]
Debt Instrument, Face Amount																																					$ 20,000
DOE Loan Guarantee [Member]
Line of Credit Facility, Maximum Borrowing Capacity																																										$ 96,800
Loan Agreement with Bpifrance [Member] | Guadeloupe 1 [Member]
Debt Instrument, Face Amount																													$ 8,900
Debt Instrument, Interest Rate, Stated Percentage																												1.93%
Long-term Debt, Gross																	$ 7,700
Loan Agreement with Société Général [Member] | Guadeloupe 1 [Member]
Debt Instrument, Face Amount									$ 8,900
Debt Instrument, Interest Rate, Stated Percentage									1.52%
Debt Instrument Number of Quarterly Payments									28
Long-term Debt, Gross																	5,900
Credit Agreements With Eight Commercial Banks [Member]
Line of Credit Facility, Maximum Borrowing Capacity																	623,000
Long-term Line of Credit, Total																	0
Letters of Credit Outstanding, Amount																	78,300
Credit Agreements With Eight Commercial Banks [Member] | Extensions of Credit in The Form of Loans and/or Letters of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity																	408,000
Credit Agreements With Eight Commercial Banks [Member] | Letter of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity																	120,000
Credit Agreements With Eight Commercial Banks [Member] | Union Bank, N.A. [Member]
Line of Credit Facility, Maximum Borrowing Capacity																	60,000
Credit Agreements With Eight Commercial Banks [Member] | HSBC Bank USA, N.A. [Member]
Line of Credit Facility, Maximum Borrowing Capacity																	35,000
Union Bank, N.A. [Member]
Line of Credit Facility, Maximum Borrowing Capacity																	60,000
Long-term Line of Credit, Total																	$ 59,100
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																	2.4
Debt Services, Coverage Ratio																	4.8
Amount Available For Dividend Distribution Percent Of Cumulative Net Income														2.0			0.66
Union Bank, N.A. [Member] | Maximum [Member]
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio														4.5
Union Bank, N.A. [Member] | Minimum [Member]
Debt Services, Coverage Ratio														1.35
HSBC Bank USA, N.A. [Member]
Line of Credit Facility, Maximum Borrowing Capacity																	$ 35,000
Long-term Line of Credit, Total																	$ 35,000
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																	2.4
Debt Services, Coverage Ratio																	4.8
Amount Available For Dividend Distribution Percent Of Cumulative Net Income																	0.66
Uncommitted Line of Credit Facility, Maximum Borrowing Capacity																	$ 20,000
Uncommitted Long-term Line of Credit																	2,500
HSBC Bank USA, N.A. [Member] | Maximum [Member]
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																4.5
Amount Available For Dividend Distribution Percent Of Cumulative Net Income																2.0
HSBC Bank USA, N.A. [Member] | Minimum [Member]
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																1.35
Surety Agreement [Member] | Chubb [Member]
Surety Bonds Available																																	$ 200,000
Surety Bonds Outstanding																	$ 182,600

[1] Financing liability is related to a sale and leaseback transaction entered into by the Seller in September 2015 under which it sold and leased back the undivided interests in the Dixie Valley power plant asset through June 2038. The lease transaction was accounted for by the Seller as a finance lease due to the Seller's continued involvement and management of the power plant and the existence of an early buy-out option in September 2024, which continues to be applicable to the Company. As per the accounting guidance, the Company retained the Seller's accounting of a "failed" sale and leaseback transaction and accordingly accounted for the liability as a financing liability. This financing liability, as well as the related power plant asset, were measured at their acquisition-date fair value.

[2] payable semi-annually

[3] payable semi-annually in arrears.

[4] payable quarterly