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

No definition available.

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

- Definition

Represents the number of employees in the company.

+ References

No definition available.

+ Details

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

- Definition

Number Of Joint Ventures

+ References

No definition available.

+ Details

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

- Definition

Total expense amount to reimburse a related party.

+ References

No definition available.

+ Details

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

- Definition

Amount of expense for incentive rights held by the managing member or general partner, of limited liability company (LLC) or limited partnership (LP).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

+ Details

Name:	us-gaap_IncentiveFeeExpense
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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864

+ Details

Name:	us-gaap_RelatedPartyTransactionAmountsOfTransaction
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

No definition available.

+ Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=opi_ReitManagementAndResearchLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- 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:

Business and Property Management Agreements with RMR (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2023 USD ($) employee joint_venture agreement	Mar. 31, 2022 USD ($)	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
Reimbursement expense	6,347	$ 5,966
RMR LLC \| Net Business Management Fees
Related Party Transaction [Line Items]
Related party transaction amount	3,951	4,710
RMR LLC \| Net Property Management and Construction Supervision Fees
Related Party Transaction [Line Items]
Related party transaction amount	6,319	6,128
RMR LLC \| Net Property Management and Construction Supervision Fees \| Buildings and Improvements
Related Party Transaction [Line Items]
Related party transaction amount	2,586	1,902
RMR LLC \| Net Property Management and Construction Supervision Fees \| Other Operating Income (Expense)
Related Party Transaction [Line Items]
Related party transaction amount	$ 3,733	$ 4,226