This element represents the aggregate sales price excluding closing costs, of real estate properties sold by the entity.

No definition available.

+ Details

Name:	opi_RealEstateAggregateSalesPrice
Namespace Prefix:	opi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Area of a real estate property.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column A)(Footnote 2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section 30
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478150/970-360-30-2

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

+ Details

Name:	us-gaap_NumberOfRealEstateProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Name:	us-gaap_RealEstatePropertiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=us-gaap_ScenarioPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=opi_RedwoodCityCAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=opi_PhiladelphiaPAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=opi_PittsfordNYMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=opi_IndianapolisINMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=opi_RestonVAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=opi_ColumbiaMDMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=opi_BaltimoreMDMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=opi_LakewoodCOMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=opi_RichmondVAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupHeldForSaleOrDisposedOfBySaleNotDiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Real Estate Properties - Disposition Activities (Details) $ in Thousands			6 Months Ended
	Jul. 30, 2026 USD ($) ft² property	Jul. 20, 2026 USD ($) ft² property	Jun. 30, 2026 USD ($) ft² property	Apr. 22, 2026 property
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Real Estate Properties [Line Items]
Number of Properties			32
Rentable Square Feet (in square feet) \| ft²			3,690,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Scenario, Plan
Real Estate Properties [Line Items]
Number of Properties				9
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Redwood City, CA \| Subsequent Event
Real Estate Properties [Line Items]
Number of Properties		1
Rentable Square Feet (in square feet) \| ft²		63,000
Gross Sales Price \| $		$ 16,500
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Philadelphia, PA \| Subsequent Event
Real Estate Properties [Line Items]
Number of Properties	1
Rentable Square Feet (in square feet) \| ft²	441,000
Gross Sales Price \| $	$ 42,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Pittsford, NY \| Scenario, Plan
Real Estate Properties [Line Items]
Number of Properties			1
Rentable Square Feet (in square feet) \| ft²			55,000
Gross Sales Price \| $			$ 3,750
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Indianapolis, IN \| Scenario, Plan
Real Estate Properties [Line Items]
Number of Properties			2
Rentable Square Feet (in square feet) \| ft²			275,000
Gross Sales Price \| $			$ 5,500
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Reston, VA \| Scenario, Plan
Real Estate Properties [Line Items]
Number of Properties			1
Rentable Square Feet (in square feet) \| ft²			275,000
Gross Sales Price \| $			$ 18,125
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Columbia, MD \| Scenario, Plan
Real Estate Properties [Line Items]
Number of Properties			2
Rentable Square Feet (in square feet) \| ft²			87,000
Gross Sales Price \| $			$ 10,300
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Baltimore, MD \| Scenario, Plan
Real Estate Properties [Line Items]
Number of Properties			1
Rentable Square Feet (in square feet) \| ft²			85,000
Gross Sales Price \| $			$ 5,050
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Lakewood, CO \| Scenario, Plan
Real Estate Properties [Line Items]
Number of Properties			1
Rentable Square Feet (in square feet) \| ft²			167,000
Gross Sales Price \| $			$ 3,700
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Richmond, VA \| Scenario, Plan
Real Estate Properties [Line Items]
Number of Properties			1
Rentable Square Feet (in square feet) \| ft²			50,000
Gross Sales Price \| $			$ 3,250
Disposal Group, Held-for-Sale or Disposed of by Sale, Not Discontinued Operations \| Scenario, Plan
Real Estate Properties [Line Items]
Number of Properties			11
Rentable Square Feet (in square feet) \| ft²			1,498,000
Gross Sales Price \| $			$ 108,175