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Lessee, Operating Lease, Number Of Renewal Options

No definition available.

Name:	opc_LesseeOperatingLeaseNumberOfRenewalOptions
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The number of finance leases.

No definition available.

Name:	opc_NumberOfFinanceLeases
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Data Type:	xbrli:integerItemType
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Period Type:	instant

Number Of Operating Leases

No definition available.

Name:	opc_NumberOfOperatingLeases
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Data Type:	xbrli:integerItemType
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Period Type:	instant

The percentage of undivided interest in property, plant and equipment.

No definition available.

Name:	opc_PercentageOfUndividedInterestPropertyPlantAndEquipment
Namespace Prefix:	opc_
Data Type:	dtr-types1:percentItemType
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Term of lessee's finance lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-3

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Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Namespace Prefix:
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