Note 13 - Puna Power Plant Lease Transactions (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2005	Dec. 31, 2015
Lease Term		31 years
Deferred Revenue, Leases, Gross		$ 83,000,000
Capital Leases, Balance Sheet, Assets by Major Class, Net	$ 28,000,000		$ 30,700,000
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	$ 32,900,000		30,200,000
Lease Payment Term	23 years
Deferred Costs, Leasing, Gross	$ 4,200,000
Restricted Cash and Cash Equivalents	2,900,000		2,100,000
Cash	$ 0		$ 0