Note 1 - Business and Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Schedule of Cash and Cash Equivalents [Table Text Block]

	December 31,
	2019		2018		2017
	(Dollars in thousands)
Cash and cash equivalents	$	71,173	$	98,802	$	47,818
Restricted cash and cash equivalents		81,937		78,693		48,825
Total cash and cash equivalents and restricted cash and cash equivalents	$	153,110	$	177,495	$	96,643

Schedule Of Estimated Useful Lives [Table Text Block]

Buildings (in years)		25
Leasehold improvements (in years)	15	-	20
Machinery and equipment — manufacturing and drilling (in years)		10
Machinery and equipment — computers (in years)	3	-	5
Office equipment — furniture and fixtures (in years)	5	-	15
Office equipment — other (in years)	5	-	10
Vehicles (in years)	5	-	7

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

	December 31,			December 31,
	2019			2018
	(Dollars in thousands)
Contract assets (*)	$	38,365		$	42,130
Contract liabilities (*)		(2,755	)		(18,402	)
Contract assets, net	$	35,610		$	23,728

	Years Ended December 31,
	2019						2018
	Contract assets			Contract liabilities			Contract assets			Contract liabilities
	(Dollars in thousands)
Recognition of contract liabilities as revenue as a result of performance obligations satisfied	$	—		$	12,675		$	—		$	33,349
Cash received in advance for which revenues have not yet recognized, net of expenditures made		—			(3,323	)		—			(38,162	)
Reduction of contract assets as a result of rights to consideration becoming unconditional		(130,918	)		—			(128,659	)		—
Contract assets recognized, net of recognized receivables		133,448			—			136,496			—
Net change in contract assets and contract liabilities	$	2,530		$	9,352		$	7,837		$	(4,813	)

Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]

	Year Ended December 31,
	2019		2018
	(Dollars in thousands)
Electricity Revenues accounted under lease accounting	$	479,059	$	481,619
Electricity, Product and Energy Storage and Management Services revenues accounted under ASC 606		266,985		237,648
Total consolidated revenues	$	746,044	$	719,267

	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,
	2019		2018		2017
	(In thousands)
Weighted average number of shares used in computation of basic earnings per share		50,867		50,643		50,110
Add:
Additional shares from the assumed exercise of employee stock options		360		326		659
Weighted average number of shares used in computation of diluted earnings per share		51,227		50,969		50,769

Redeemable Noncontrolling Interest [Table Text Block]

	2019			2018
	(Dollars in thousands)
Redeemable noncontrolling interest as of January 1,	$	8,603		$	6,416
Redeemable noncontrolling interest in results of operation of a consolidated subsidiary		1,132			990
Cash paid to noncontrolling interest		(252	)		—
Increase in share of redeemable noncontrolling interest		—			1,528
Currency translation adjustments		(233	)		(331	)
Redeemable noncontrolling interest as of December 31,	$	9,250		$	8,603

ROA Asset [Member]

Notes Tables

Schedule Of Estimated Useful Lives [Table Text Block]

	(in years)
Land		1	-	35
Vehicles			5
Building			15