Note 8 - Property, Plant and Equipment and Construction-in-process (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Property, Plant and Equipment [Table Text Block]

	December 31,
	2019			2018
	(Dollars in thousands)
Land owned by the Company where the geothermal resource is located	$	38,049		$	38,060
Leasehold improvements		7,757			5,718
Machinery and equipment		230,465			208,646
Land, buildings and office equipment		39,099			35,708
Vehicles		8,021			22,074
Geothermal and recovered energy generation power plants, including geothermal wells and exploration and resource development costs:
United States of America, net of cash grants		2,160,910			2,065,377
Foreign countries		721,824			710,775
Asset retirement cost		19,824			11,448
		3,225,949			3,097,806
Less accumulated depreciation		(1,254,534	)		(1,138,228	)
Property, plant and equipment, net	$	1,971,415		$	1,959,578

Construction In Progress [Table Text Block]

	December 31,
	2019		2018
	(Dollars in thousands)
Projects under exploration and development:
Up-front bonus costs	$	17,018	$	17,018
Exploration and development costs		66,916		53,237
Interest capitalized		703		703
		84,637		70,958
Projects under construction:
Up-front bonus costs		27,473		27,473
Drilling and construction costs		258,484		160,398
Interest capitalized		5,961		2,861
		291,918		190,732
Total	$	376,555	$	261,690

Rollforward Of Construction In Process [Table Text Block]

	Projects under exploration and development
	Up-front Bonus Costs			Exploration and Development Costs			Interest Capitalized		Total
	(Dollars in thousands)
Balance at December 31, 2016	$	17,385		$	36,359		$	703	$	54,447
Cost incurred during the year		—			11,224			—		11,224
Write off of unsuccessful exploration costs		(367	)		(1,429	)		—		(1,796	)
Balance at December 31, 2017		17,018			46,154			703		63,875
Cost incurred during the year		—			7,209			—		7,209
Write off of unsuccessful exploration costs		—			(126	)		—		(126	)
Balance at December 31, 2018		17,018			53,237			703		70,958
Cost incurred during the year		—			17,215			—		17,215
Transfer of projects under exploration and development to projects under construction		—			(3,536	)		—		(3,536	)
Balance at December 31, 2019	$	17,018		$	66,916		$	703	$	84,637

	Projects under construction
	Up-front Bonus Costs			Drilling and Construction Costs			Interest Capitalized			Total
	(Dollars in thousands)
Balance at December 31, 2016	$	37,713		$	202,211		$	12,338		$	252,262
Cost incurred during the year		—			231,926			7,300			239,226
Transfer of completed projects to property, plant and equipment		(10,240	)		(235,194	)		(16,387	)		(261,821	)
Balance at December 31, 2017		27,473			198,943			3,251			229,667
Cost incurred during the year		—			219,610			—			219,610
Cost write off		—			(1,380	)		—			(1,380	)
Fair value of projects under construction acquired in a business combination		—			4,668			—			4,668
Transfer of completed projects to property, plant and equipment		—			(261,443	)		(390	)		(261,833	)
Balance at December 31, 2018		27,473			160,398			2,861			190,732
Cost incurred during the year		—			264,137			3,100			267,237
Transfer of projects under exploration and development to projects under construction		—			3,536			—			3,536
Insurance recoveries		—			(35,435	)		—			(35,435	)
Transfer of completed projects to property, plant and equipment		—			(134,152	)		—			(134,152	)
Balance at December 31, 2019	$	27,473		$	258,484		$	5,961		$	291,918