Annual report pursuant to Section 13 and 15(d)

Earnings Per Share ("EPS") and Earnings Per Unit (“EPU”) (Details)

v2.4.1.9
Earnings Per Share ("EPS") and Earnings Per Unit (“EPU”) (Details) (USD $)
In Thousands, except Per Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Numerator:                      
Income (loss) from continuing operations $ 5,874us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest $ 13,727us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest $ 9,248us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest $ 5,660us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest $ 14,432us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest $ 10,974us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest $ (232)us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest $ 11,662us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest $ 34,509us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest $ 36,836us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest $ 7,967us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
Gain on sales of real estate, net                 10,671us-gaap_GainLossOnSaleOfPropertiesNetOfApplicableIncomeTaxes 9,016us-gaap_GainLossOnSaleOfPropertiesNetOfApplicableIncomeTaxes 21us-gaap_GainLossOnSaleOfPropertiesNetOfApplicableIncomeTaxes
Preferred share/ unit dividends/ distributions (3,552)us-gaap_PreferredStockDividendsIncomeStatementImpact (3,553)us-gaap_PreferredStockDividendsIncomeStatementImpact (4,344)us-gaap_PreferredStockDividendsIncomeStatementImpact (4,490)us-gaap_PreferredStockDividendsIncomeStatementImpact (4,490)us-gaap_PreferredStockDividendsIncomeStatementImpact (4,490)us-gaap_PreferredStockDividendsIncomeStatementImpact (4,885)us-gaap_PreferredStockDividendsIncomeStatementImpact (6,106)us-gaap_PreferredStockDividendsIncomeStatementImpact (15,939)us-gaap_PreferredStockDividendsIncomeStatementImpact (19,971)us-gaap_PreferredStockDividendsIncomeStatementImpact (20,844)us-gaap_PreferredStockDividendsIncomeStatementImpact
Issuance costs associated with redeemed preferred shares 0us-gaap_OtherPreferredStockDividendsAndAdjustments 0us-gaap_OtherPreferredStockDividendsAndAdjustments (1,769)us-gaap_OtherPreferredStockDividendsAndAdjustments 0us-gaap_OtherPreferredStockDividendsAndAdjustments 0us-gaap_OtherPreferredStockDividendsAndAdjustments 0us-gaap_OtherPreferredStockDividendsAndAdjustments (2,904)us-gaap_OtherPreferredStockDividendsAndAdjustments 0us-gaap_OtherPreferredStockDividendsAndAdjustments (1,769)us-gaap_OtherPreferredStockDividendsAndAdjustments (2,904)us-gaap_OtherPreferredStockDividendsAndAdjustments (1,827)us-gaap_OtherPreferredStockDividendsAndAdjustments
(Income) loss from continuing operations attributable to noncontrolling interests                 (4,955)us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity (4,486)us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity 1,309us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity
Income from continuing operations attributable to restricted units                 (432)us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic (414)us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic (469)us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic
Numerator for basic and diluted EPS/EPU from continuing operations attributable to COPT/COPLP common shareholders/unitholders                 22,085ofc_NetIncomeLossfromContinuingOperationsAvailabletoCommonStockholdersBasicandDiluted 18,077ofc_NetIncomeLossfromContinuingOperationsAvailabletoCommonStockholdersBasicandDiluted (13,843)ofc_NetIncomeLossfromContinuingOperationsAvailabletoCommonStockholdersBasicandDiluted
Discontinued operations 22us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 191us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax (198)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 11us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 71,907us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax (12,974)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax (4,502)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 1,261us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 26us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 55,692us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax 12,353us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
Discontinued operations attributable to noncontrolling interests                 4us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest (3,351)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest (673)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest
Numerator for basic and diluted EPS/EPU on net income (loss)attributable to COPT/COPLP common shareholders/common unitholders                 22,115ofc_NetIncomeLossAttributabletoCommonStockholdersBasicandDiluted 70,418ofc_NetIncomeLossAttributabletoCommonStockholdersBasicandDiluted (2,163)ofc_NetIncomeLossAttributabletoCommonStockholdersBasicandDiluted
Denominator (all weighted averages):                      
Denominator for basic EPS (common shares)                 88,092us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 85,167us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 73,454us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
Dilutive effect of share-based compensation awards                 171us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements 57us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements 0us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements
Denominator for basic and diluted EPS (common shares)                 88,263us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 85,224us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 73,454us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
Basic EPS:                      
Income (loss) from continuing operations (in dollars per share/unit)                 $ 0.25us-gaap_IncomeLossFromContinuingOperationsPerBasicShare [1] $ 0.21us-gaap_IncomeLossFromContinuingOperationsPerBasicShare [1] $ (0.19)us-gaap_IncomeLossFromContinuingOperationsPerBasicShare [1]
Discontinued operations (in dollars per share/unit)                 $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare [1] $ 0.62us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare [1] $ 0.16us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare [1]
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit) $ 0.01us-gaap_EarningsPerShareBasic $ 0.22us-gaap_EarningsPerShareBasic $ 0.02us-gaap_EarningsPerShareBasic $ 0.00us-gaap_EarningsPerShareBasic $ 0.94us-gaap_EarningsPerShareBasic $ (0.09)us-gaap_EarningsPerShareBasic $ (0.16)us-gaap_EarningsPerShareBasic $ 0.11us-gaap_EarningsPerShareBasic $ 0.25us-gaap_EarningsPerShareBasic [1] $ 0.83us-gaap_EarningsPerShareBasic [1] $ (0.03)us-gaap_EarningsPerShareBasic [1]
Diluted EPS:                      
Income (loss) from continuing operations (in dollars per share/unit)                 $ 0.25us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare [1] $ 0.21us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare [1] $ (0.19)us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare [1]
Discontinued operations (in dollars per share/unit)                 $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare [1] $ 0.62us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare [1] $ 0.16us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare [1]
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit) $ 0.01us-gaap_EarningsPerShareDiluted $ 0.22us-gaap_EarningsPerShareDiluted $ 0.02us-gaap_EarningsPerShareDiluted $ 0.00us-gaap_EarningsPerShareDiluted $ 0.94us-gaap_EarningsPerShareDiluted $ (0.09)us-gaap_EarningsPerShareDiluted $ (0.16)us-gaap_EarningsPerShareDiluted $ 0.11us-gaap_EarningsPerShareDiluted $ 0.25us-gaap_EarningsPerShareDiluted [1] $ 0.83us-gaap_EarningsPerShareDiluted [1] $ (0.03)us-gaap_EarningsPerShareDiluted [1]
Corporate Office Properties, L.P.                      
Numerator:                      
Income (loss) from continuing operations 5,874us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		13,727us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		9,248us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		5,660us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		14,432us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		10,974us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(232)us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		11,662us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		34,509us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		36,836us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		7,967us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Gain on sales of real estate, net                 10,671us-gaap_GainLossOnSaleOfPropertiesNetOfApplicableIncomeTaxes
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		9,016us-gaap_GainLossOnSaleOfPropertiesNetOfApplicableIncomeTaxes
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		21us-gaap_GainLossOnSaleOfPropertiesNetOfApplicableIncomeTaxes
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Preferred share/ unit dividends/ distributions (3,717)us-gaap_PreferredStockDividendsIncomeStatementImpact
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(3,718)us-gaap_PreferredStockDividendsIncomeStatementImpact
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(4,509)us-gaap_PreferredStockDividendsIncomeStatementImpact
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(4,655)us-gaap_PreferredStockDividendsIncomeStatementImpact
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(4,655)us-gaap_PreferredStockDividendsIncomeStatementImpact
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(4,655)us-gaap_PreferredStockDividendsIncomeStatementImpact
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(5,050)us-gaap_PreferredStockDividendsIncomeStatementImpact
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(6,271)us-gaap_PreferredStockDividendsIncomeStatementImpact
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(16,599)us-gaap_PreferredStockDividendsIncomeStatementImpact
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(20,631)us-gaap_PreferredStockDividendsIncomeStatementImpact
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(21,504)us-gaap_PreferredStockDividendsIncomeStatementImpact
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Issuance costs associated with redeemed preferred shares 0us-gaap_OtherPreferredStockDividendsAndAdjustments
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		0us-gaap_OtherPreferredStockDividendsAndAdjustments
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(1,769)us-gaap_OtherPreferredStockDividendsAndAdjustments
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		0us-gaap_OtherPreferredStockDividendsAndAdjustments
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		0us-gaap_OtherPreferredStockDividendsAndAdjustments
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		0us-gaap_OtherPreferredStockDividendsAndAdjustments
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(2,904)us-gaap_OtherPreferredStockDividendsAndAdjustments
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		0us-gaap_OtherPreferredStockDividendsAndAdjustments
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(1,769)us-gaap_OtherPreferredStockDividendsAndAdjustments
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(2,904)us-gaap_OtherPreferredStockDividendsAndAdjustments
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(1,827)us-gaap_OtherPreferredStockDividendsAndAdjustments
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
(Income) loss from continuing operations attributable to noncontrolling interests                 (3,281)us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(2,977)us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		1,206us-gaap_IncomeLossFromContinuingOperationsAttributableToNoncontrollingEntity
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Income from continuing operations attributable to restricted units                 (432)us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(414)us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(469)us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Numerator for basic and diluted EPS/EPU from continuing operations attributable to COPT/COPLP common shareholders/unitholders                 23,099ofc_NetIncomeLossfromContinuingOperationsAvailabletoCommonStockholdersBasicandDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		18,926ofc_NetIncomeLossfromContinuingOperationsAvailabletoCommonStockholdersBasicandDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(14,606)ofc_NetIncomeLossfromContinuingOperationsAvailabletoCommonStockholdersBasicandDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Discontinued operations 22us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		191us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(198)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		11us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		71,907us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(12,974)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(4,502)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		1,261us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		26us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		55,692us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		12,353us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Discontinued operations attributable to noncontrolling interests                 5us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(930)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		(699)us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxAttributableToNoncontrollingInterest
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Numerator for basic and diluted EPS/EPU on net income (loss)attributable to COPT/COPLP common shareholders/common unitholders                 $ 23,130ofc_NetIncomeLossAttributabletoCommonStockholdersBasicandDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 73,688ofc_NetIncomeLossAttributabletoCommonStockholdersBasicandDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ (2,952)ofc_NetIncomeLossAttributabletoCommonStockholdersBasicandDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Denominator (all weighted averages):                      
Denominator for basic EPS (common shares)                 91,989us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		89,036us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		77,689us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Dilutive effect of share-based compensation awards                 171us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		57us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		0us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Denominator for basic and diluted EPS (common shares)                 92,160us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		89,093us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		77,689us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
Basic EPS:                      
Income (loss) from continuing operations (in dollars per share/unit)                 $ 0.25us-gaap_IncomeLossFromContinuingOperationsPerBasicShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ 0.21us-gaap_IncomeLossFromContinuingOperationsPerBasicShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ (0.19)us-gaap_IncomeLossFromContinuingOperationsPerBasicShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2]
Discontinued operations (in dollars per share/unit)                 $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ 0.62us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ 0.15us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2]
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit) $ 0.01us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.22us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.02us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.00us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.94us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ (0.09)us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ (0.16)us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.11us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.25us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ 0.83us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ (0.04)us-gaap_EarningsPerShareBasic
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2]
Diluted EPS:                      
Income (loss) from continuing operations (in dollars per share/unit)                 $ 0.25us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ 0.21us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ (0.19)us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2]
Discontinued operations (in dollars per share/unit)                 $ 0.00us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ 0.62us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ 0.15us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2]
Net income (loss) attributable to COPT common shareholders (in dollars per share/unit) $ 0.01us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.22us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.02us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.00us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.94us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ (0.09)us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ (0.16)us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.11us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		$ 0.25us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ 0.83us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2] $ (0.04)us-gaap_EarningsPerShareDiluted
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember 		[2]
[1] Basic and diluted earnings per common share are calculated based on amounts attributable to common shareholders of Corporate Office Properties Trust.
[2] Basic and diluted earnings per common unit are calculated based on amounts attributable to common unitholders of Corporate Office Properties, L.P.