Asset Acquisition, Acquisition Related Costs

No definition available.

Name:	opi_AssetAcquisitionAcquisitionRelatedCosts
Namespace Prefix:	opi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Asset Acquisition, Consideration Transferred

+ References

No definition available.

+ Details

Name:	opi_AssetAcquisitionConsiderationTransferred
Namespace Prefix:	opi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Noncontrolling Interest, Number Of Buildings

+ References

No definition available.

+ Details

Name:	opi_NoncontrollingInterestNumberOfBuildings
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

Represents number of leases executed during the reporting period.

+ References

No definition available.

+ Details

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

- Definition

Represents committed expenditures for operating leases executed during the period.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

Name:	opi_OperatingLeasesCommittedExpendituresOnLeasesExecutedInPeriodAreaOfLeasedProperty
Namespace Prefix:	opi_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

Name:	opi_OperatingLeasesCommittedExpendituresOnLeasesExecutedInPeriodCommittedButUnspentTenantRelatedObligations
Namespace Prefix:	opi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the weighted average lease term of operating leases.

+ References

No definition available.

+ Details

Name:	opi_OperatingLeasesWeightedAverageLeaseTerm
Namespace Prefix:	opi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

- Definition

The cash outflow from the acquisition of a piece of land, anything permanently fixed to it, including buildings, structures on it and so forth; includes real estate intended to generate income for the owner; excludes real estate acquired for use by the owner.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Carrying amount as of the balance sheet date of investments in land and buildings held for sale, excluding real estate considered to be inventory of the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(f))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

Name:	us-gaap_RealEstateHeldforsale
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_RealEstatePropertiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementOperatingActivitiesSegmentAxis=us-gaap_SegmentContinuingOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstatePropertiesAxis=us-gaap_UnconsolidatedPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=opi_JointVentureProperty2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=opi_JointVentureProperty1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementGeographicalAxis=opi_BostonMAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_LandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Real Estate Properties - Additional Information (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Feb. 29, 2020 USD ($)	Mar. 31, 2020 USD ($) ft² lease property joint_venture	Mar. 31, 2019 USD ($)
Real Estate Properties [Line Items]
Real estate held for sale		$ 3,515,885
Number of joint ventures \| joint_venture		2
Number of leases entered \| lease		27
Rentable square feet (in sqft) \| ft²		600,000
Weighted average lease term		4 years 9 months 18 days
Expenditures committed on leases		$ 12,930
Committed but unspent tenant related obligations estimated		57,348
Payments to acquire real estate		$ 11,864	$ 0
Continuing operations
Real Estate Properties [Line Items]
Number of properties \| property		184
Rentable area of properties (in square feet) \| ft²		24,900,000
Unconsolidated Joint Ventures
Real Estate Properties [Line Items]
Number of properties \| property		3
Rentable area of properties (in square feet) \| ft²		443,867
Number of buildings, noncontrolling interest \| property		3
Joint Venture 2
Real Estate Properties [Line Items]
Ownership percentage		51.00%
Joint Venture 1
Real Estate Properties [Line Items]
Ownership percentage		50.00%
Boston, MA
Real Estate Properties [Line Items]
Payments to acquire real estate	$ 11,864
Acquisition related costs	364
Land \| Boston, MA
Real Estate Properties [Line Items]
Purchase price of asset acquisition	2,618
Building \| Boston, MA
Real Estate Properties [Line Items]
Purchase price of asset acquisition	$ 9,246