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Organization (Details 2) (Corporate Office Properties, L.P.)	12 Months Ended
	Dec. 31, 2012 Trustee	Dec. 31, 2011
Common Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership	95.00%	94.00%
Number of trustees controlling additional common units	3
Additional percentage of common units controlled by trustees (as a percent)	4.00%
Series G Preferred Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership		100.00%
Series H Preferred Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership	100.00%	100.00%
Series I Preferred Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership	0.00%	0.00%
Series J Preferred Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership	100.00%	100.00%
Series K Preferred Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership	100.00%	100.00%
Series L Preferred Units
Forms of ownership in Operating Partnership and ownership percentage by the entity
Percentage ownership in operating partnership	100.00%

X

- Definition

Additional percentage of the operating partnership's common units controlled by trustees, either directly or through ownership by other entities or family members.

+ References

No definition available.

+ Details

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Namespace Prefix:	ofc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Represents the number of trustees who control common units in addition to those owned by the entity.

+ References

No definition available.

+ Details

Name:	ofc_NumberOfTrusteesControllingAdditionalCommonUnits
Namespace Prefix:	ofc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	ofc_OwnershipInSubsidiaryPercentageLineItems
Namespace Prefix:	ofc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The number of units or percentage investment held by the managing member or general partner of the LLC or LP.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Practice Bulletin (PB)

-Number 14

-Paragraph 15

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 272

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

+ Details

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