Note 1 - Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

Schedule of Cash and Cash Equivalents [Table Text Block]

	December 31,
	2020		2019		2018
	(Dollars in thousands)
Cash and cash equivalents	$	448,252	$	71,173	$	98,802
Restricted cash and cash equivalents		88,526		81,937		78,693
Total cash and cash equivalents and restricted cash and cash equivalents	$	536,778	$	153,110	$	177,495

Schedule Of Estimated Useful Lives [Table Text Block]

	Years
Buildings		25
Leasehold improvements	15	-	30
Machinery and equipment — manufacturing and drilling		10
Machinery and equipment — computers	3	-	5
Energy storage equipment		15
Office equipment — furniture and fixtures	5	-	15
Office equipment — other	5	-	10
Vehicles	5	-	7

Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block]

	December 31,			December 31,
	2020			2019
	(Dollars in thousands)
Contract assets (*)	$	24,544		$	38,365
Contract liabilities (*)	$	(11,179	)	$	(2,755	)

	Years Ended December 31,
	2020						2019
	Contract assets			Contract liabilities			Contract assets			Contract liabilities
	(Dollars in thousands)
Recognition of contract liabilities as revenue as a result of performance obligations satisfied	$	—		$	5,336		$	—		$	12,675
Cash received in advance for which revenues have not yet recognized, net of expenditures made		—			(11,177	)		—			(3,323	)
Reduction of contract assets as a result of rights to consideration becoming unconditional		(145,548	)		—			(130,918	)		—
Contract assets recognized, net of recognized receivables		129,144			—			133,448			—
Net change in contract assets and contract liabilities	$	(16,404	)	$	(5,841	)	$	2,530		$	9,352

Accounting Standards Update and Change in Accounting Principle [Table Text Block]

	Year Ended December 31,
	2020		2019
	(Dollars in thousands)
Electricity revenues accounted under lease accounting	$	473,260	$	479,059
Electricity, Product and Energy Storage revenues accounted under ASC 606		232,082		266,985
Total consolidated revenues	$	705,342	$	746,044

	According to the previous accounting policy		The change			As presented according to Topic 842
	(Dollars in thousands)
As of January 1, 2019:
Prepaid expenses and other	$	51,441	$	(35,385	)	$	16,056
Deferred financing and lease costs, net		3,242		(1,659	)		1,583
Property, plant and equipment, net		1,959,578		(12,855	)		1,946,723
Operating leases right of use		—		62,244			62,244
Finance leases right of use		—		13,476			13,476
Accounts payable and accrued expenses		116,362		(2,860	)		113,502
Current maturity of operating lease liabilities		—		7,532			7,532
Current maturity of finance lease liabilities		—		2,841			2,841
Other long-term liabilities		16,087		(9,970	)		6,117
Long term portion of operating lease liabilities		—		17,668			17,668
Long term portion of finance lease liabilities		—		10,668			10,668
Retained earnings		422,222		(58	)		422,164

Schedule of Weighted Average Number of Shares [Table Text Block]

	Year Ended December 31,
	2020		2019		2018
	(In thousands)
Weighted average number of shares used in computation of basic earnings per share		51,567		50,867		50,643
Add:
Additional shares from the assumed exercise of employee stock options		370		360		326
Weighted average number of shares used in computation of diluted earnings per share		51,937		51,227		50,969

Redeemable Noncontrolling Interest [Table Text Block]

	2020			2019
	(Dollars in thousands)
Redeemable noncontrolling interest as of January 1,	$	9,250		$	8,603
Redeemable noncontrolling interest in results of operation of a consolidated subsidiary		1,330			1,132
Cash paid to noncontrolling interest		(1,779	)		(252	)
Currency translation adjustments		1,029			(233	)
Redeemable noncontrolling interest as of December 31,	$	9,830		$	9,250

Accounts Receivable, Allowance for Credit Loss [Table Text Block]

	Year Ended December 31,
	2020
	(Dollars in thousands)
Beginning balance of the allowance for expected credit losses	$	755
Change in the provision for expected credit losses for the period		(158	)
Ending balance of the allowance for expected credit losses	$	597

ROA Asset [Member]

Notes Tables

Schedule Of Estimated Useful Lives [Table Text Block]

	(in years)
Vehicles	5
Building	15