Note 2 - New Accounting Pronouncements (Details) $ in Millions	Sep. 30, 2015 USD ($)
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Debt Issuance Costs	$ 20.3

Amount of the effect of a change in accounting principle on debt issuance costs.

No definition available.

Name:	ora_NewAccountingPronouncementOrChangeInAccountingPrincipleEffectOfChangeOnDebtIssuanceCosts
Namespace Prefix:	ora_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant