Note 12 - Puna Power Plant Transactions	12 Months Ended
Dec. 31, 2019
Projected [Member]
Notes to Financial Statements
Leases of Lessee Disclosure [Text Block]	NOTE 12 — PUNA POWER PLANT TRANSACTIONS In 2005, the Company’s wholly owned subsidiary in Hawaii, Puna Geothermal Ventures (“PGV”), entered into lease transactions involving the original geothermal power plant of the Puna complex located on the Big Island (the “Puna Power Plant”). In December 2019, PGV and HELCO executed an amended and restated PPA for power sold from the Puna complex power plant. The new PPA extends the term until 2052 with an increased contract capacity of 46 MW and a fixed price of $70 per MWh with no escalation all energy purchased during any contract year up to 227,000 MWh and $40 per MWh above 227,000 MWh. In addition, annual capacity payments under the contract are expected to be approximately $19.5 million. The amended and restated PPA was filed with the Public Utilities Commission on December 31, 2019. In connection with the execution of the amended and restated PPA, the Company paid $20.5 million to effectively terminate the lease transactions involving the original power plant which gives the Company the ability to satisfy its obligations under the new PPA. The Company recorded this payment under deposits and other in its consolidated balance sheets as an incremental cost in obtaining the new amended and restated PPA as described above. As a result, the Company has no obligation for future minimum payments as of December 31, 2019. Prior to the amended and restated PPA, PGV leased the Puna Power Plant to an unrelated company under a 31-year head lease (the “Head Lease”) in return for prepaid lease payments in the total amount of $83.0 million (the “Deferred Lease Income”). The unrelated company (the “Lessor”) simultaneously leased back the Puna Power Plant to PGV under a 23-year lease (the “Project Lease”). PGV’s rent obligations under the Project Lease were paid solely from revenues generated by the Puna Power Plant under a PPA that PGV had with HELCO. The Head Lease and the Project Lease were non-recourse lease obligations to the Company. PGV’s rights in the geothermal resource and the related PPA were not leased to the Lessor as part of the Head Lease but are part of the Lessor’s security package. The Head Lease and the Project Lease were accounted for separately. Each was classified as an operating lease in accordance with the accounting standards for leases. The Project Lease transaction was included in the initial recognition of operating leases right of use asset and liability on the consolidated balance sheets as of January 1, 2019 as further described under Note 1 to the consolidated financial statements under the caption New Accounting Pronouncements, Leases. The Deferred Lease Income was amortized into revenue using the straight-line method, over the 31-year term of the Head Lease. Deferred transaction costs amounting to $4.2 million were amortized using the straight-line method, over the 23-year term of the Project Lease. The carrying value of the leased assets as of December 31, 2018 was $19.7 million, net of accumulated depreciation of $33.1 million.

Note 12 - Puna Power Plant Transactions

12 Months Ended

Dec. 31, 2019

Leases of Lessee Disclosure [Text Block]

NOTE 12 — PUNA POWER PLANT TRANSACTIONS

In 2005, the Company’s wholly owned subsidiary in Hawaii, Puna Geothermal Ventures (“PGV”), entered into lease transactions involving the original geothermal power plant of the Puna complex located on the Big Island (the “Puna Power Plant”).

In December 2019, PGV and HELCO executed an amended and restated PPA for power sold from the Puna complex power plant. The new PPA extends the term until 2052 with an increased contract capacity of 46 MW and a fixed price of $70 per MWh with no escalation all energy purchased during any contract year up to 227,000 MWh and $40 per MWh above 227,000 MWh. In addition, annual capacity payments under the contract are expected to be approximately $19.5 million. The amended and restated PPA was filed with the Public Utilities Commission on December 31, 2019.

In connection with the execution of the amended and restated PPA, the Company paid $20.5 million to effectively terminate the lease transactions involving the original power plant which gives the Company the ability to satisfy its obligations under the new PPA. The Company recorded this payment under deposits and other in its consolidated balance sheets as an incremental cost in obtaining the new amended and restated PPA as described above. As a result, the Company has no obligation for future minimum payments as of December 31, 2019.

Prior to the amended and restated PPA, PGV leased the Puna Power Plant to an unrelated company under a 31-year head lease (the “Head Lease”) in return for prepaid lease payments in the total amount of $83.0 million (the “Deferred Lease Income”). The unrelated company (the “Lessor”) simultaneously leased back the Puna Power Plant to PGV under a 23-year lease (the “Project Lease”). PGV’s rent obligations under the Project Lease were paid solely from revenues generated by the Puna Power Plant under a PPA that PGV had with HELCO. The Head Lease and the Project Lease were non-recourse lease obligations to the Company. PGV’s rights in the geothermal resource and the related PPA were not leased to the Lessor as part of the Head Lease but are part of the Lessor’s security package.

The Head Lease and the Project Lease were accounted for separately. Each was classified as an operating lease in accordance with the accounting standards for leases. The Project Lease transaction was included in the initial recognition of operating leases right of use asset and liability on the consolidated balance sheets as of January 1, 2019 as further described under Note 1 to the consolidated financial statements under the caption New Accounting Pronouncements, Leases. The Deferred Lease Income was amortized into revenue using the straight-line method, over the 31-year term of the Head Lease. Deferred transaction costs amounting to $4.2 million were amortized using the straight-line method, over the 23-year term of the Project Lease. The carrying value of the leased assets as of December 31, 2018 was $19.7 million, net of accumulated depreciation of $33.1 million.