Represents the number of agreements with RMR LLC to provide management services to the company.

No definition available.

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Namespace Prefix:	opi_
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Balance Type:	na
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- Definition

Represents the number of employees in the company.

+ References

No definition available.

+ Details

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Namespace Prefix:	opi_
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Balance Type:	na
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- Definition

Number Of Joint Ventures

+ References

No definition available.

+ Details

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

- Definition

Amount of expense for incentive fee based on performance under arrangement to manage operations, including, but not limited to, investment.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(b))
-Publisher FASB
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-Topic 850
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-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of transactions with related party during the financial reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

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-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-3

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c)(2)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

+ Details

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Data Type:	xbrli:stringItemType
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- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=opi_ReitManagementAndResearchLLCMember
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- Details

Name:	us-gaap_RelatedPartyTransactionAxis=opi_NetBusinessManagementFeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=opi_NetPropertyManagementandConstructionSupervisionFeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=opi_BuildingsAndImprovementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_OtherOperatingIncomeExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=opi_PropertyOperatingExpensesMember
Namespace Prefix:
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Business and Property Management Agreements with RMR (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) joint_venture agreement employee	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Related Party Transaction [Line Items]
Number of joint ventures \| joint_venture			2
RMR LLC
Related Party Transaction [Line Items]
Number of employees \| employee			0
Number of agreements \| agreement			2
Incentive fee	$ 0		$ 0		$ 0
RMR LLC \| Net Business Management Fees
Related Party Transaction [Line Items]
Related party transaction amount	3,637	$ 4,260	11,180	$ 13,462
RMR LLC \| Net Property Management and Construction Supervision Fees
Related Party Transaction [Line Items]
Related party transaction amount	5,465	6,502	17,947	19,024
RMR LLC \| Net Property Management and Construction Supervision Fees \| Buildings and Improvements
Related Party Transaction [Line Items]
Related party transaction amount	1,747	2,506	6,695	6,787
RMR LLC \| Net Property Management and Construction Supervision Fees \| Other Operating Income (Expense)
Related Party Transaction [Line Items]
Related party transaction amount	3,718	3,996	11,252	12,237
RMR LLC \| Property Operating Expenses
Related Party Transaction [Line Items]
Related party transaction amount	$ 6,331	$ 6,268	$ 19,295	$ 18,281