Note 1 - Business and Significant Accounting Policies 1 (Details Textual) $ / shares in Units, $ in Thousands				2 Months Ended	3 Months Ended		12 Months Ended
	Jun. 27, 2022 USD ($)	Jun. 22, 2022 USD ($) $ / shares shares	Feb. 19, 2021 USD ($)	Feb. 28, 2023 USD ($)	Dec. 31, 2022 USD ($) $ / shares	Jun. 30, 2022 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Cash, FDIC Insured Amount					$ 10,000		$ 10,000	$ 31,000
Cash, Uninsured Amount					64,300		64,300	64,300
Accounts Receivable, after Allowance for Credit Loss, Current, Total					128,818		128,818	122,944
Interest Costs Capitalized							18,727	14,582	$ 10,409
Exploration Abandonment and Impairment Expense							828	0	0
Amortization of Debt Issuance Costs							4,200	3,200	3,500
Write off of Deferred Debt Issuance Cost							0
Impairment of Long-Lived Assets to be Disposed of							0
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax, Ending Balance					$ 3,100		3,100	1,200
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Total							$ (2,486)	$ (3,236)	$ 3,813
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares) | shares							29,200	142,400	369,700
Payments of Dividends, Total							$ 27,100	$ 27,000	$ 22,500
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share) | $ / shares							$ 0.48	$ 0.48	$ 0.44
Proceeds from Notes Payable, Total							$ 419,698	$ 0	$ 0
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares		$ 0.001			$ 0.001		$ 0.001	$ 0.001
Purchase of Capped Call Instruments							$ 24,538	$ (0)	(0)
Payments for Repurchase of Common Stock						$ 18,000	17,964	(0)	(0)
Treasury Stock, Shares, Acquired (in shares) | shares						258,667
Treasury Stock Acquired, Average Cost Per Share (in dollars per share) | $ / shares						$ 69.45
Insurance Recoveries							(0)	248	$ 20,743
Loss from Catastrophes			$ 9,100
General and Administrative Expense [Member]
Accounts Receivable, Credit Loss Expense (Reversal)								$ 3,000
Fire [Member]
Insurance Recoveries							21,800
Increase (Decrease) in Insurance Settlements Receivable							(8,000)
Gain on Business Interruption Insurance Recovery							13,800
Senior Unsecured Bonds, Series 3 [Member]
Repayments of Long-Term Debt, Total	$ 221,900
Extinguishment of Debt, Amount	218,000
Interest Paid, Including Capitalized Interest, Operating and Investing Activities, Total	2,800
Debt Instrument, Unamortized Premium, Total	1,100
Call Option [Member]
Option Indexed to Issuer's Equity, Shares (in shares) | shares		4,800,000
Option Indexed to Issuer's Equity, Strike Price (in dollars per share) | $ / shares		$ 90.27
Option Indexed to Issuer's Equity, Cap Price		107.63%
Option Indexed to Issuer's Equity, Premium Percentage		55.00%
Purchase of Capped Call Instruments						$ 24,500
Convertible Senior Notes [Member]
Amortization of Debt Issuance Costs							$ 1,100
Debt Instrument, Convertible, Conversion Price (in dollars per share) | $ / shares		$ 90.27			$ 90.27		$ 90.27
Debt Instrument, Face Amount	431,250	$ 375,000
Debt Instrument, Interest Rate, Stated Percentage		2.50%
Proceeds from Notes Payable, Total	$ 56,250
Debt Instrument, Convertible, Threshold Trading Days		20
Debt Instrument, Convertible, Threshold Consecutive Trading Days		30
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger		130.00%
Debt Instrument, Convertible, Threshold Trading Days, Measurement Period Request (Year)		5 years
Debt Instrument, Convertible, Maximum Percentage of Stock Price Trigger Per $1000		98.00%
Debt Instrument, Convertible, Conversion Shares Per $1000		11.0776
Debt Instrument, Redemption Price, Percentage		100.00%
Debt Instrument, Cumulative Sinking Fund Payments		$ 0
Debt Issuance Costs, Gross					$ 11,600		$ 11,600
Debt Instrument, Interest Rate, Effective Percentage					3.10%		3.10%
Galena 2 Power Purchase Agreement [Member]
Termination Fees							$ 0
Minimum [Member]
Finite-Lived Intangible Asset, Useful Life (Year)							6 years
Standard Product Warranty, Term (Year)							1 year
Minimum [Member] | Fleet Vehicles [Member]
Lessee, Finance Lease, Term of Contract (Year)					4 years		4 years
Minimum [Member] | Viridity Energy, Inc. [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life (Year)							6 years
Maximum [Member]
Finite-Lived Intangible Asset, Useful Life (Year)							19 years
Standard Product Warranty, Term (Year)							2 years
Maximum [Member] | Fleet Vehicles [Member]
Lessee, Finance Lease, Term of Contract (Year)					5 years		5 years
Maximum [Member] | Viridity Energy, Inc. [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life (Year)							19 years
Power Plants [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life (Year)							15 years
Power Plants [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life (Year)							30 years
North Brawley Geothermal Power Plant [Member]
Asset Impairment Charges, Total					$ 30,500
Energy Storage Projects and Customer Related Assets [Member]
Property, Plant and Equipment, Disposals							$ 2,100
Kenya Power and Lighting Co Limited [Member]
Accounts Receivable, Past Due					27,000		27,000
Kenya Power and Lighting Co Limited [Member] | Subsequent Event [Member]
Proceeds, Overdue Accounts Receivable				$ 15,200
ENEE [Member]
Accounts Receivable, Past Due					13,900		$ 13,900
ENEE [Member] | Subsequent Event [Member]
Proceeds, Overdue Accounts Receivable				$ 2,600
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Primary Customers [Member]
Concentration Risk, Percentage							60.00%	58.00%
Total Receivables [Member] | Customer Concentration Risk [Member]
Financing Receivable, after Allowance for Credit Loss, Total					89,800		$ 89,800	$ 86,400
Non-US [Member]
Accounts Receivable, after Allowance for Credit Loss, Current, Total					$ 78,900		$ 78,900	$ 77,500