Note 9 - Property, Plant and Equipment and Construction-in-process (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

Property, Plant and Equipment [Table Text Block]

	December 31,
	2016			2015
	(Dollars in thousands)
Land owned by the Company where the geothermal resource is located	$	31,904		$	31,465
Leasehold improvements		3,848			3,691
Machinery and equipment		152,821			133,457
Land, buildings and office equipment		28,634			29,247
Automobiles		11,161			7,782
Geothermal and recovered energy generation power plants, including geothermal wells and exploration and resource development costs:
United States of America, net of cash grants and impairment charges		1,658,195			1,637,081
Foreign countries		541,626			494,105
Asset retirement cost		8,669			7,961
		2,436,858			2,344,789
Less accumulated depreciation		(880,480	)		(785,454	)
Property, plant and equipment, net	$	1,556,378		$	1,559,335

Construction In Progress [Table Text Block]

	December 31,
	2016		2015
	(Dollars in thousands)
Projects under exploration and development:
Up-front bonus lease costs	$	17,385	$	26,491
Exploration and development costs		36,359		35,726
Interest capitalized		703		703
		54,447		62,920
Projects under construction:
Up-front bonus lease costs		37,713		27,473
Drilling and construction costs		202,211		150,467
Interest capitalized		12,338		7,975
		252,262		185,915
Total	$	306,709	$	248,835

Rollforward Of Construction In Process [Table Text Block]

	Projects under Exploration and Development
	Up-front Bonus Lease Costs			Exploration and Development Costs			Interest Capitalized			Total
	(Dollars in thousands)
Balance at December 31, 2013	$	30,141		$	38,220		$	1,278		$	69,639
Cost incurred during the year		—			19,231			—			19,231
Write off of unsuccessful exploration costs		(3,523	)		(11,474	)		(442	)		(15,439	)
Balance at December 31, 2014		26,618			45,977			836			73,431
Cost incurred during the year		37			10,104			869			11,010
Write off of unsuccessful exploration costs		(164	)		(1,415	)		—			(1,579	)
Transfer of projects under exploration and development to projects under construction		—			(18,940	)		(1,002	)		(19,942	)
Balance at December 31, 2015		26,491			35,726			703			62,920
Cost incurred during the year		1,514			25,165			—			26,679
Write off of unsuccessful exploration costs		(380	)		(2,637	)		—			(3,017	)
Transfer of projects under exploration and development to projects under construction		(10,240	)		(21,895	)		—			(32,135	)
Balance at December 31, 2016	$	17,385		$	36,359		$	703		$	54,447

	Projects under Construction
	Up-front Bonus Lease Costs		Drilling and Construction Costs			Interest Capitalized			Total
	(Dollars in thousands)
Balance at December 31, 2013	$	27,473	$	184,766		$	6,948		$	219,187
Cost incurred during the year		—		132,597			3,206			135,803
Transfer of completed projects to property, plant and equipment		—		(105,126	)		(970	)		(106,096	)
Sale of property, plant and equipment		—		(24,692	)		(911	)		(25,603	)
Balance at December 31, 2014		27,473		187,545			8,273			223,291
Cost incurred during the year		—		140,977			3,556			144,533
Transfer of exploration and development projects to projects under construction		—		18,940			1,002			19,942
Transfer of completed projects to property, plant and equipment		—		(196,995	)		(4,856	)		(201,851	)
Sale of property, plant and equipment		—		—			—			—
Balance at December 31, 2015		27,473		150,467			7,975			185,915
Cost incurred during the year		—		116,247			6,510			122,757
Transfer of exploration and development projects to projects under construction		10,240		21,895			—			32,135
Transafer of completed projects to property, plant and equipment		—		(86,398	)		(2,147	)		(88,545	)
Balance at December 31, 2016	$	37,713	$	202,211		$	12,338		$	252,262