Name:	opi_AggregateNetBookValueOfRealEstatePropertiesCollateralized
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The aggregate principal amount on real estate properties serving as collateral for debt as of the balance sheet date.

No definition available.

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

The option to extend the maturity date subject to certain conditions and the payment of a fee under the credit facility.

No definition available.

Name:	opi_DebtInstrumentContingentOptionToExtendMaturityDate
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Debt Instrument, Number Of Contingent Options To Extend

No definition available.

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

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

No definition available.

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Data Type:	xbrli:integerItemType
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Period Type:	instant

Represents the calculation of the average interest rate weighted by the amount of long-term debt outstanding by type or by instrument at that time.

No definition available.

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Namespace Prefix:	opi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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Data Type:	dtr-types:percentItemType
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Face (par) amount of debt instrument at time of issuance.

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

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

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Period Type:	instant

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.

No definition available.

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Namespace Prefix:	us-gaap_
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Period Type:	duration

Face (par) amount of the original debt instrument that was repurchased.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Name:	us-gaap_LineOfCredit
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Balance Type:	credit
Period Type:	instant

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

No definition available.

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

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.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

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The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	duration

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Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
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Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
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Name:	us-gaap_DebtInstrumentAxis=opi_A2650SeniorUnsecuredNotesDue2026Member
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