Number Of Joint Ventures

No definition available.

Name:	opi_NumberOfJointVentures
Namespace Prefix:	opi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents number of leases executed during the reporting period.

+ References

No definition available.

+ Details

Name:	opi_NumberOfOperatingLeaseExecuted
Namespace Prefix:	opi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents committed expenditures for operating leases executed during the period.

+ References

No definition available.

+ Details

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

- Definition

Represents the area of leased property related to operating leases executed during the period.

+ References

No definition available.

+ Details

Name:	opi_OperatingLeasesCommittedExpendituresOnLeasesExecutedInPeriodAreaOfLeasedProperty
Namespace Prefix:	opi_
Data Type:	dtr-types:areaItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents committed but unspent tenant related obligations based on executed operating leases as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	opi_OperatingLeasesCommittedExpendituresOnLeasesExecutedInPeriodCommittedButUnspentTenantRelatedObligations
Namespace Prefix:	opi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the weighted average lease term of operating leases.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

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

No definition available.

+ Details

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

- Definition

Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

+ Details

Name:	us-gaap_EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(d))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

Name:	us-gaap_RealEstateInvestmentPropertyAtCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

No definition available.

+ Details

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

- Details

Name:	us-gaap_RealEstatePropertiesAxis=us-gaap_UnconsolidatedPropertiesMember
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:

- Details

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

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=opi_JointVentureProperty1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementOperatingActivitiesSegmentAxis=us-gaap_SegmentContinuingOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Real Estate Properties - Narrative (Details) $ in Thousands		3 Months Ended
Real Estate Properties - Narrative (Details) $ in Thousands	May 18, 2026 USD ($) ft² property	Mar. 31, 2026 USD ($) ft² joint_venture property lease	Dec. 31, 2025 USD ($)
Real Estate Properties [Line Items]
Real estate aggregate undepreciated carrying value		$ 3,681,681	$ 3,676,695
Number of leases entered \| lease		13
Rentable square feet (in square feet) \| ft²		212,000
Weighted average lease term		4 years 6 months
Expenditures committed on leases		$ 4,516
Committed but unspent tenant related obligations estimated		$ 54,390
Number of joint ventures \| joint_venture		1
Unconsolidated Joint Ventures
Real Estate Properties [Line Items]
Unamortized basis difference		$ 638
Disposal Group, Held-for-Sale or Disposed of by Sale, Not Discontinued Operations \| Subsequent Event
Real Estate Properties [Line Items]
Number of properties \| property	1
Rentable square feet (in square feet) \| ft²	275,000
Gross sales price	$ 18,125
Joint Venture
Real Estate Properties [Line Items]
Ownership interest		51.00%
Joint Venture \| Unconsolidated Joint Ventures
Real Estate Properties [Line Items]
Number of properties \| property		2
Rentable square feet (in square feet) \| ft²		346,000
Continuing operations
Real Estate Properties [Line Items]
Number of properties \| property		122
Rentable square feet (in square feet) \| ft²		17,113,000
Real estate aggregate undepreciated carrying value		$ 3,681,681