Note 12 - Puna Power Plant Transactions (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2005	Dec. 31, 2018
Lease Term		31 years
Deferred Lease Income, before Accumulated Amortization		$ 83,000
Lease Payment Term		23 years
Deferred Costs, Leasing, Gross			$ 4,200
Capital Leases, Balance Sheet, Assets by Major Class, Net, Total			19,700
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation			$ 33,100
Puna Geothermal Power Plant [Member]
Operating Leases, Future Minimum Payments Due, Total	$ 0
Amended and Restated PPA [Member]
Price Per MWh Under 227,000 MWh	$ 70
Price Per MWh Over 227,000 MWh	$ 40
Long-term Contract for Purchase of Electric Power, Estimated Annual Cost	$ 19,500
Loss on Contract Termination	$ 20,500