SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION - Additional Information (Details) $ in Thousands	12 Months Ended
Dec. 31, 2022 USD ($)
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract]
Mortgage debt, net	$ 83
Aggregate cost for federal income tax purposes	$ 7,360,476
Useful life of buildings and improvements	40 years
Useful life of equipment	7 years

Represents the estimated economic life of buildings and improvements on which depreciation in the latest income statement was computed.

No definition available.

+ Details

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Namespace Prefix:	opi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the estimated economic life of equipment on which depreciation in the latest income statement was computed.

+ References

No definition available.

+ Details

Name:	opi_RealEstateAndAccumulatedDepreciationEquipmentLifeUsedForDepreciation
Namespace Prefix:	opi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	srt_RealEstateAndAccumulatedDepreciationDisclosureAbstract
Namespace Prefix:	srt_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Cost basis of real estate investments for federal income tax purposes for entities with a substantial portion of business acquiring and holding investment real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Footnote 6
-Subsection 28

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 970
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Footnote 6))
-URI https://asc.fasb.org/extlink&oid=120402810&loc=d3e638233-123024

+ Details

Name:	srt_RealEstateFederalIncomeTaxBasis
Namespace Prefix:	srt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G))
-URI https://asc.fasb.org/extlink&oid=120402547&loc=d3e617274-123014

+ Details

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Balance Type:	debit
Period Type:	instant