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Organization (Details) - Dec. 31, 2018 ft² in Millions | a | MW | ft² | Property
--- | --- | --- | --- | ---
Operating properties [Member] |  |  |  |
Investments in real estate |  |  |  |
Number of real estate properties |  |  |  | 163
Area of real estate property (in sqft or acres) | ft² |  |  | 18.1 |
Operating properties [Member] | Office Properties [Member] |  |  |  |
Investments in real estate |  |  |  |
Number of real estate properties |  |  |  | 145
Area of real estate property (in sqft or acres) | ft² |  |  | 15.1 |
Operating properties [Member] | Single-tenant data centers [Member] |  |  |  |
Investments in real estate |  |  |  |
Number of real estate properties |  |  |  | 18
Area of real estate property (in sqft or acres) | ft² |  |  | 3.0 |
Operating wholesale data centers [Member] |  |  |  |
Investments in real estate |  |  |  |
Critical load (in megawatts) | MW |  | 19.25 |  |
Properties under, or contractually committed for, construction or approved for redevelopment [Member] |  |  |  |
Investments in real estate |  |  |  |
Number of real estate properties |  |  |  | 10
Area of real estate property (in sqft or acres) | ft² |  |  | 1.3 |
Properties under, or contractually committed for, construction or approved for redevelopment [Member] | Office Properties [Member] |  |  |  |
Investments in real estate |  |  |  |
Number of real estate properties |  |  |  | 6
Properties under, or contractually committed for, construction or approved for redevelopment [Member] | Single-tenant data centers [Member] |  |  |  |
Investments in real estate |  |  |  |
Number of real estate properties |  |  |  | 4
Properties under, or contractually committed for, construction or approved for redevelopment [Member] | Partially operational properties [Member] |  |  |  |
Investments in real estate |  |  |  |
Number of real estate properties |  |  |  | 2
Land controlled for future development [Member] |  |  |  |
Investments in real estate |  |  |  |
Area of real estate property (in sqft or acres) | 900 |  | 11.7 |
Other land [Member] |  |  |  |
Investments in real estate |  |  |  |
Area of real estate property (in sqft or acres) | a | 150 |  |  |
GI-COPT [Member] | Operating properties [Member] | Single-tenant data centers [Member] |  |  |  |
Investments in real estate |  |  |  |
Number of real estate properties |  |  |  | 6

X
- Definition Represents the amount of the critical load of the property. Critical load is the amount of megawatts of power made available for the exclusive use tenants in the property. + References No definition available. + Details
Name: | ofc_CriticalLoad
Namespace Prefix: | ofc_
Data Type: | num:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Area of a real estate property. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | num:areaItemType
Balance Type: | na
Period Type: | instant

X
- Definition The number of real estate properties owned as of the balance sheet date. + References No definition available. + Details
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Balance Type: | na
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- 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
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Namespace Prefix: | us-gaap_
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Period Type: | duration

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- Details
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Namespace Prefix: |
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Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
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- Details
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- Details
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Namespace Prefix: |
Data Type: | na
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- Details
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Namespace Prefix: |
Data Type: | na
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- Details
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Namespace Prefix: |
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- Details
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Data Type: | na
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Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |