Note 10 - Commitments and Contingencies (Details Textual) $ in Millions		4 Months Ended
Mar. 29, 2016 USD ($)	Sep. 30, 2018
Loss Contingency, New Claims Filed, Number		4
Former Local Sales Representative vs. Ormat [Member] \| Pending Litigation [Member]
Loss Contingency, Damages Sought, Value	$ 4.6
Loss Contingency, Additional Damages Sought for Ormat Geothermal Products Sales in Chile, Percent	3.75%
Loss Contingency, Damages Sought, Ormat Geothermal Products Sales in Chile, Period	10 years

The percentage of the Ormat geothermal products sales in Chile award the plaintiff seeks in the legal matter.

No definition available.

Name:	ora_LossContingencyAdditionalDamagesSoughtForOrmatGeothermalProductsSalesInChilePercent
Namespace Prefix:	ora_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the loss contingency period of the Ormat geothermal product sales in Chile award in the legal matter.

+ References

No definition available.

+ Details

Name:	ora_LossContingencyDamagesSoughtOrmatGeothermalProductsSalesInChilePeriod
Namespace Prefix:	ora_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

+ Details

Name:	us-gaap_LossContingencyDamagesSoughtValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The total number of new claims filed pertaining to a loss contingency during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

+ Details

Name:	us-gaap_LossContingencyNewClaimsFiledNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	srt_LitigationCaseAxis=ora_FormerLocalSalesRepresentativeVsOrmatMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LitigationStatusAxis=us-gaap_PendingLitigationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: