Number Of Properties Securing Debt

No definition available.

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Period Type:	instant

- Definition

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

+ References

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of unamortized debt discount (premium) and debt issuance costs.

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Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details

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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.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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+ Details

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

- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

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

- Details

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- Details

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Name:	us-gaap_DebtInstrumentAxis=opi_A2400SeniorUnsecuredNotesDue2027Member
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Name:	us-gaap_DebtInstrumentAxis=opi_A3450SeniorUnsecuredNotesDue2031Member
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Name:	us-gaap_DebtInstrumentAxis=opi_SeniorUnsecuredNotes6.375PercentDueIn2050Member
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Fair Value of Assets and Liabilities - Financial Instruments (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($) property
Fair Value of Financial Instruments
Senior notes		$ 2,477,730	$ 2,033,242
Mortgage notes payable		$ 98,460	169,729
4.15% Senior Unsecured Notes Due 2022
Fair Value of Financial Instruments
Interest rate (as a percent)		4.15%
4.00% Senior Unsecured Notes Due 2022
Fair Value of Financial Instruments
Interest rate (as a percent)		4.00%
4.25% Senior Unsecured Notes Due 2024
Fair Value of Financial Instruments
Interest rate (as a percent)		4.25%
4.50% Senior Unsecured Notes Due 2025
Fair Value of Financial Instruments
Interest rate (as a percent)		4.50%
2.650% Senior Unsecured Notes Due 2026
Fair Value of Financial Instruments
Interest rate (as a percent)		2.65%
2.400% Senior Unsecured Notes Due 2027
Fair Value of Financial Instruments
Interest rate (as a percent)		2.40%
3.450% Senior Unsecured Notes Due 2031
Fair Value of Financial Instruments
Interest rate (as a percent)		3.45%
5.875% Senior Unsecured Notes Due 2046
Fair Value of Financial Instruments
Interest rate (as a percent)		5.875%
6.375% Senior Unsecured Notes Due 2050
Fair Value of Financial Instruments
Interest rate (as a percent)		6.375%
Senior Notes And Mortgages
Fair Value of Financial Instruments
Unamortized debt premiums, discounts and issuance costs		$ 34,414	$ 39,871
Mortgages
Fair Value of Financial Instruments
Number of properties securing debt \| property			3
Repayments of debt	$ 71,000
Carrying Amount
Fair Value of Financial Instruments
Fair value of financial instruments		2,576,190	$ 2,202,971
Carrying Amount \| 4.15% Senior Unsecured Notes Due 2022
Fair Value of Financial Instruments
Senior notes		0	298,853
Carrying Amount \| 4.00% Senior Unsecured Notes Due 2022
Fair Value of Financial Instruments
Senior notes		299,270	298,579
Carrying Amount \| 4.25% Senior Unsecured Notes Due 2024
Fair Value of Financial Instruments
Senior notes		344,011	342,299
Carrying Amount \| 4.50% Senior Unsecured Notes Due 2025
Fair Value of Financial Instruments
Senior notes		638,507	635,921
Carrying Amount \| 2.650% Senior Unsecured Notes Due 2026
Fair Value of Financial Instruments
Senior notes		297,057	0
Carrying Amount \| 2.400% Senior Unsecured Notes Due 2027
Fair Value of Financial Instruments
Senior notes		346,713	0
Carrying Amount \| 3.450% Senior Unsecured Notes Due 2031
Fair Value of Financial Instruments
Senior notes		395,701	0
Carrying Amount \| 5.875% Senior Unsecured Notes Due 2046
Fair Value of Financial Instruments
Senior notes		0	301,264
Carrying Amount \| 6.375% Senior Unsecured Notes Due 2050
Fair Value of Financial Instruments
Senior notes		156,471	156,326
Carrying Amount \| Mortgages
Fair Value of Financial Instruments
Mortgage notes payable		98,460	169,729
Fair Value
Fair Value of Financial Instruments
Fair value of financial instruments		2,701,023	2,335,352
Fair Value \| 4.15% Senior Unsecured Notes Due 2022
Fair Value of Financial Instruments
Senior notes		0	306,192
Fair Value \| 4.00% Senior Unsecured Notes Due 2022
Fair Value of Financial Instruments
Senior notes		306,717	306,756
Fair Value \| 4.25% Senior Unsecured Notes Due 2024
Fair Value of Financial Instruments
Senior notes		371,980	365,435
Fair Value \| 4.50% Senior Unsecured Notes Due 2025
Fair Value of Financial Instruments
Senior notes		697,460	688,399
Fair Value \| 2.650% Senior Unsecured Notes Due 2026
Fair Value of Financial Instruments
Senior notes		302,846	0
Fair Value \| 2.400% Senior Unsecured Notes Due 2027
Fair Value of Financial Instruments
Senior notes		346,456	0
Fair Value \| 3.450% Senior Unsecured Notes Due 2031
Fair Value of Financial Instruments
Senior notes		393,680	0
Fair Value \| 5.875% Senior Unsecured Notes Due 2046
Fair Value of Financial Instruments
Senior notes		0	322,028
Fair Value \| 6.375% Senior Unsecured Notes Due 2050
Fair Value of Financial Instruments
Senior notes		180,533	171,590
Fair Value \| Mortgages
Fair Value of Financial Instruments
Mortgage notes payable		$ 101,351	$ 174,952