Quarterly report pursuant to Section 13 or 15(d)

Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Details 2)

v2.4.1.9
Earnings Per Share ("EPS") and Earnings Per Unit ("EPU") (Details 2)
In Thousands, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Conversion of common units    
Antidilutive securities    
Antidilutive securities excluded from computation of diluted earnings per share (in shares) 3,732us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= ofc_ExchangeableCommonUnitsMember 		3,958us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= ofc_ExchangeableCommonUnitsMember
Conversion of Series I Preferred Units    
Antidilutive securities    
Antidilutive securities excluded from computation of diluted earnings per share (in shares) 176us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= ofc_WeightedAverageConvertiblePreferredUnitMember 		176us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= ofc_WeightedAverageConvertiblePreferredUnitMember
Conversion of Series K Preferred Shares    
Antidilutive securities    
Antidilutive securities excluded from computation of diluted earnings per share (in shares) 434us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= ofc_WeightedAverageConvertiblePreferredStockMember 		434us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= ofc_WeightedAverageConvertiblePreferredStockMember
Weighted average restricted shares    
Antidilutive securities    
Antidilutive securities excluded from computation of diluted earnings per share (in shares) 400us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_RestrictedStockMember 		390us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_RestrictedStockMember
Weighted average options    
Antidilutive securities    
Antidilutive securities excluded from computation of diluted earnings per share (in shares) 474us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EmployeeStockOptionMember 		588us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EmployeeStockOptionMember
Corporate Office Properties, L.P. | Weighted average restricted shares    
Antidilutive securities    
Antidilutive securities excluded from computation of diluted earnings per share (in shares) 400us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		390us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_RestrictedStockMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Corporate Office Properties, L.P. | Weighted average options    
Antidilutive securities    
Antidilutive securities excluded from computation of diluted earnings per share (in shares) 474us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EmployeeStockOptionMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		588us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_EmployeeStockOptionMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Corporate Office Properties, L.P. | Conversion of Series I preferred units    
Antidilutive securities    
Antidilutive securities excluded from computation of diluted earnings per share (in shares) 176us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= ofc_SeriesIPreferredUnitsMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		176us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= ofc_SeriesIPreferredUnitsMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Corporate Office Properties, L.P. | Conversion of Series K preferred units    
Antidilutive securities    
Antidilutive securities excluded from computation of diluted earnings per share (in shares) 434us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= ofc_SeriesKPreferredUnitsMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		434us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= ofc_SeriesKPreferredUnitsMember
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember