Real Estate Properties - Real Estate Properties Narrative (Details) $ in Thousands	12 Months Ended
Dec. 31, 2025 USD ($) ft² property lease	Dec. 31, 2024 USD ($)
Real Estate Properties [Line Items]
Real estate aggregate undepreciated carrying value	$ 3,676,695	$ 3,657,559
Number of leases entered \| lease	46
Rentable square feet (in square feet) \| ft²	974,000
Weighted average lease term	6 years 8 months 12 days
Expenditures committed on leases	$ 27,854
Operating leases committed expenditures on leases executed in period committed but unspent tenant related obligations	$ 55,076
Joint Venture Property 1
Real Estate Properties [Line Items]
Percentage of ownership interest	51.00%
Joint Venture Property 1 \| Unconsolidated Properties
Real Estate Properties [Line Items]
Number of Properties (in properties) \| property	2
Area of properties (in square feet) \| ft²	346,000
Continuing Operations
Real Estate Properties [Line Items]
Number of Properties (in properties) \| property	122
Area of properties (in square feet) \| ft²	17,113,000
Real estate aggregate undepreciated carrying value	$ 3,676,695

Represents number of leases executed during the reporting period.

No definition available.

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- Definition

Represents committed expenditures for operating leases executed during the period.

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Represents the weighted average lease term of operating leases.

+ References

No definition available.

+ Details

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Namespace Prefix:	opi_
Data Type:	xbrli:durationItemType
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- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:areaItemType
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- 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

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- Definition

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

+ References

No definition available.

+ Details

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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

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- 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

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- Details

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- Details

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