Represents the number of other governments that are tenants of the entity.

No definition available.

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

- Definition

Represents the number of state governments that are tenants of the entity.

+ References

No definition available.

+ Details

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

- Definition

The number of states in which real estate owned by the entity is located as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	opi_NumberOfStatesInWhichRealEstatePropertiesHeld
Namespace Prefix:	opi_
Data Type:	xbrli:integerItemType
Balance Type:	na
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_ConcentrationRiskLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-SubTopic 10
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-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592

+ Details

Name:	us-gaap_ConcentrationRiskPercentage1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- 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

- Details

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Namespace Prefix:
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- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_CustomerConcentrationRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_MajorCustomersAxis=opi_USGovernmentStateGovernmentsAndOtherGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MajorCustomersAxis=opi_USGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConcentrationRiskByTypeAxis=us-gaap_GeographicConcentrationRiskMember
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Data Type:	na
Balance Type:
Period Type:

- Details

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- Details

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Balance Type:
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
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Balance Type:
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- Details

Name:	srt_StatementGeographicalAxis=stpr_GA
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Concentration (Details)	12 Months Ended
Concentration (Details)	Dec. 31, 2021 property government_tenant state_government	Dec. 31, 2020 state_government government_tenant	Dec. 31, 2019 government_tenant state_government
Concentration Risk [Line Items]
Number of other governments \| government_tenant	4	2	2
Number of properties (in properties)	178
Number of states in which acquired properties located	33
Annualized Rental Income, Excluding Properties Classified as Discontinued Operations \| Tenant Concentration \| U S Government, State Governments, and Other Governments
Concentration Risk [Line Items]
Number of state governments \| state_government	11	11	11
Concentration risk, percentage	28.90%	35.30%	35.50%
Annualized Rental Income, Excluding Properties Classified as Discontinued Operations \| Tenant Concentration \| U.S. Government
Concentration Risk [Line Items]
Concentration risk, percentage	19.50%	25.20%	25.00%
Annualized Rental Income, Excluding Properties Classified as Discontinued Operations \| Geographic Concentration Risk \| Virginia
Concentration Risk [Line Items]
Concentration risk, percentage	12.40%
Annualized Rental Income, Excluding Properties Classified as Discontinued Operations \| Geographic Concentration Risk \| California
Concentration Risk [Line Items]
Concentration risk, percentage	10.50%
Annualized Rental Income, Excluding Properties Classified as Discontinued Operations \| Geographic Concentration Risk \| Washington, D.C.
Concentration Risk [Line Items]
Concentration risk, percentage	9.80%
Annualized Rental Income, Excluding Properties Classified as Discontinued Operations \| Geographic Concentration Risk \| Illinois
Concentration Risk [Line Items]
Concentration risk, percentage	9.20%
Annualized Rental Income, Excluding Properties Classified as Discontinued Operations \| Geographic Concentration Risk \| Georgia
Concentration Risk [Line Items]
Concentration risk, percentage	8.20%