The number of properties serving as collateral for debt as of the balance sheet date.

No definition available.

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

- Definition

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

+ References

No definition available.

+ Details

Name:	opi_RealEstateAndAccumulatedDepreciationBuildingsAndImprovementsLifeUsedForDepreciation
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

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 28
-Paragraph Column A
-Footnote 2
-Publisher SEC

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 28
-Paragraph Column I
-Publisher SEC

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 28
-Paragraph Column H
-Publisher SEC

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 28
-Paragraph Column G
-Publisher SEC

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 28
-Paragraph Column F
-Publisher SEC

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

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 28
-Paragraph Column D
-Publisher SEC

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 28
-Paragraph Column C
-Publisher SEC

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 28
-Paragraph Column B
-Publisher SEC

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column F))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column E))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column D))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column C))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column I))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-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 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column G))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column H))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

+ Details

Name:	srt_RealEstateAndAccumulatedDepreciationLineItems
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
-Name Regulation S-X (SX)
-Number 210
-Section 12
-Subsection 28
-Paragraph Column E
-Footnote 6
-Publisher SEC

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column E)(Footnote 6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482949/835-30-55-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69B

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69C

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482900/835-30-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(a)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G)(Footnote 3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478322/948-310-S50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

+ Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_MortgagesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=opi_A7671MortgageNotesPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=opi_A9.000SeniorSecuredNotesPayableDueInSeptember2029Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=opi_A9.000SeniorSecuredNotesPayableDueInMarch2029Member
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:	us-gaap_DebtInstrumentAxis=opi_A3.250SeniorSecuredNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=opi_A12.000DebtorInPossessionTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

SCHEDULE III REAL ESTATE AND ACCUMULATED DEPRECIATION - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($) property	Apr. 22, 2026	Feb. 04, 2026 USD ($)	Nov. 05, 2025 USD ($)	Oct. 30, 2025	Jan. 01, 2025 USD ($)
Real estate and accumulated depreciation
Mortgage debt, net	$ 3,480
Aggregate cost for federal income tax purposes	$ 7,069,942
Useful life of buildings and improvements	40 years
Useful life of equipment	7 years
Mortgage notes payable
Real estate and accumulated depreciation
Number of properties used to secured mortgage note \| property	7
Line of Credit
Real estate and accumulated depreciation
Maximum borrowing capacity on revolving credit facility	$ 425,000					$ 100,000
Line of Credit \| Revolving credit facility
Real estate and accumulated depreciation
Number of properties used to secured mortgage note \| property	19
Maximum borrowing capacity on revolving credit facility	$ 325,000
Line of Credit \| Secured Debt
Real estate and accumulated depreciation
Number of properties used to secured mortgage note \| property	19
Mortgage note payable, 7.671% interest rate, due in 2028 \| Mortgage notes payable
Real estate and accumulated depreciation
Number of properties used to secured mortgage note \| property	2
Principal balance	$ 54,300
Interest rate (as a percent)	7.671%
Senior secured notes, 9.000% interest rate, due in September 2029
Real estate and accumulated depreciation
Interest rate (as a percent)	9.00%
Senior secured notes, 9.000% interest rate, due in September 2029 \| Senior Notes
Real estate and accumulated depreciation
Number of properties used to secured mortgage note \| property	19
Principal balance	$ 610,000
Interest rate (as a percent)	9.00%				9.00%
Senior secured notes, 9.000% interest rate, due in March 2029
Real estate and accumulated depreciation
Interest rate (as a percent)	9.00%
Senior secured notes, 9.000% interest rate, due in March 2029 \| Senior Notes
Real estate and accumulated depreciation
Number of properties used to secured mortgage note \| property	17
Principal balance	$ 300,000
Interest rate (as a percent)	9.00%
Senior secured notes, 9.000% interest rate, due in March 2029 \| Senior Notes \| Subsequent Event
Real estate and accumulated depreciation
Interest rate (as a percent)		9.00%
Senior secured notes, 3.250% interest rate, due in 2027
Real estate and accumulated depreciation
Interest rate (as a percent)	3.25%
Senior secured notes, 3.250% interest rate, due in 2027 \| Senior Notes
Real estate and accumulated depreciation
Number of properties used to secured mortgage note \| property	35
Principal balance	$ 445,000
Interest rate (as a percent)	3.25%
Senior secured notes, 3.250% interest rate, due in 2027 \| Senior Notes \| Subsequent Event
Real estate and accumulated depreciation
Interest rate (as a percent)		3.25%
Debtor-in-possession term loan, 12.000% interest rate, due in 2026 \| Secured Debt
Real estate and accumulated depreciation
Principal balance				$ 125,000
Interest rate (as a percent)	12.00%
Debtor-in-possession term loan, 12.000% interest rate, due in 2026 \| Secured Debt \| Subsequent Event
Real estate and accumulated depreciation
Principal balance			$ 125,000
Interest rate (as a percent)			12.00%