Note 2 - Business Acquisitions and Others - Fair Value of Amounts of Identified Assets and Liabilities Assumed in a Business Combination (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Apr. 24, 2018	Dec. 31, 2017	Dec. 31, 2016
Goodwill (2)		$ 19,950		$ 21,037	$ 6,650
U.S. Geothermal [Member]
Cash and cash equivalents and restricted cash			$ 37,900
Property, plant and equipment and construction-in-process			77,300
Intangible assets (1)	[1]		127,000
Goodwill (2)	[2]		12,700
Deferred taxes			1,700
Total assets acquired			256,600
Other working capital			(8,200)
Long-term term debt			(98,300)
Asset retirement obligation			(9,000)
Noncontrolling interest			(34,900)
Total liabilities assumed			(150,400)
Total assets acquired, and liabilities assumed, net			$ 106,200

[1] Intangible assets are primarily related to long-term electricity power purchase agreements and depreciated over an average of 19 years.

[2] Goodwill is primarily related to the expected synergies in operations as a result of the purchase transaction. The goodwill is allocated to the Electricity segment and not deductible for tax purposes.