Name:	ofc_ConstructionContractAndOtherServiceExpenses
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Income (Loss) from Equity Method Investments Allocable to Depreciation, Amortization and Interest Expense

No definition available.

Name:	ofc_IncomeLossfromEquityMethodInvestmentsAllocabletoDepreciationAmortizationandInterestExpense
Namespace Prefix:	ofc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Income (Loss) in Non-Real Estate Equity Method Investments

No definition available.

Name:	ofc_IncomeLossinNonRealEstateEquityMethodInvestments
Namespace Prefix:	ofc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the computation of NOI from service operations, which is the difference between Construction contract and other service revenues and Construction contract and other service expenses.

No definition available.

Name:	ofc_NetOperatingIncomeLossFromServiceOperations
Namespace Prefix:	ofc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Reconciliation of Operating Income from Unconsolidated Joint Ventures to Equity Method Investments [Abstract]

No definition available.

Name:	ofc_ReconciliationofOperatingIncomefromUnconsolidatedJointVenturestoEquityMethodInvestmentsAbstract
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- References

No definition available.

Name:	ofc_SegmentReportingRevenueReconcilingItemAbstract
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Unconsolidated Joint Venture Net Operating Income Allocable to Parent

No definition available.

Name:	ofc_UnconsolidatedJointVentureNetOperatingIncomeAllocabletoParent
Namespace Prefix:	ofc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of revenue earned from products sold or services provided under the terms of a contract, including, but not limited to, government contracts and construction contracts, classified as other.

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

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(12))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(10))
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(13)(f))
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Name:	us-gaap_IncomeLossFromEquityMethodInvestments
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Balance Type:	credit
Period Type:	duration

- References

No definition available.

Name:	us-gaap_OperatingIncomeLossAbstract
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Data Type:	xbrli:stringItemType
Balance Type:	na
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The aggregate revenue from real estate operations during the reporting period.

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

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).