Annual report pursuant to Section 13 and 15(d)

Equity - COPT and Subsidiaries (Details)

v2.4.1.9
Equity - COPT and Subsidiaries (Details) (USD $)
1 Months Ended 12 Months Ended 0 Months Ended
Nov. 30, 2014
Mar. 31, 2013
Oct. 31, 2012
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Jul. 16, 2013
Jun. 16, 2014
Apr. 22, 2013
Preferred Stock                  
Number of shares issued       7,431,667us-gaap_PreferredStockSharesIssued          
Aggregate liquidation preference       $ 199,083,000us-gaap_PreferredStockLiquidationPreferenceValue $ 249,083,000us-gaap_PreferredStockLiquidationPreferenceValue        
Stock redeemed or called during period value       50,000,000us-gaap_StockRedeemedOrCalledDuringPeriodValue 84,750,000us-gaap_StockRedeemedOrCalledDuringPeriodValue 55,000,000us-gaap_StockRedeemedOrCalledDuringPeriodValue      
Common Shares                  
Shares issued to the public 5,520,000us-gaap_StockIssuedDuringPeriodSharesNewIssues 4,485,000us-gaap_StockIssuedDuringPeriodSharesNewIssues              
Per share value of common and preferred shares issued to the public (in dollars per share) $ 27.30ofc_StockIssuedDuringPeriodPerShareValueNewIssues $ 26.34ofc_StockIssuedDuringPeriodPerShareValueNewIssues              
Net proceeds from issue of shares after underwriter discounts but before offering expenses 148,900,000us-gaap_StockIssuedDuringPeriodValueNewIssues 118,100,000us-gaap_StockIssuedDuringPeriodValueNewIssues   148,666,000us-gaap_StockIssuedDuringPeriodValueNewIssues 117,961,000us-gaap_StockIssuedDuringPeriodValueNewIssues        
At-market-stock, offering program established, aggregate value     150,000,000.0ofc_AtMarketStockOfferingProgramEstablishedAggregateValue            
Number of common shares for each converted common unit (in shares)       1ofc_OperatingPartnershipUnitConversionRateToShares          
Number of operating partnerships units converted into common shares (in units)       140,149us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits 311,343us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits 234,246us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits      
Dividends declared per common share       $ 1.1000us-gaap_CommonStockDividendsPerShareDeclared $ 1.10us-gaap_CommonStockDividendsPerShareDeclared $ 1.10us-gaap_CommonStockDividendsPerShareDeclared      
Common Stock Issued to Public Under At-the-Market Program                  
Common Shares                  
Shares issued to the public         1,500,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementEquityComponentsAxis
= ofc_CommonStockIssuedtoPublicUnderAttheMarketProgramMember
  1,500,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementEquityComponentsAxis
= ofc_CommonStockIssuedtoPublicUnderAttheMarketProgramMember
   
Net proceeds from issue of shares after underwriter discounts but before offering expenses             38,500,000us-gaap_StockIssuedDuringPeriodValueNewIssues
/ us-gaap_StatementEquityComponentsAxis
= ofc_CommonStockIssuedtoPublicUnderAttheMarketProgramMember
   
Issuance of stock, weighted average price per share             $ 26.05ofc_IssuanceofStockWeightedAveragePricePerShare
/ us-gaap_StatementEquityComponentsAxis
= ofc_CommonStockIssuedtoPublicUnderAttheMarketProgramMember
   
Payments of stock issuance costs             586,000us-gaap_PaymentsOfStockIssuanceCosts
/ us-gaap_StatementEquityComponentsAxis
= ofc_CommonStockIssuedtoPublicUnderAttheMarketProgramMember
   
At-market stock, offering program established, remaining capacity       110,900,000ofc_AtMarketStockOfferingProgramEstablishedRemainingCapacity
/ us-gaap_StatementEquityComponentsAxis
= ofc_CommonStockIssuedtoPublicUnderAttheMarketProgramMember
         
Preferred Shares                  
Preferred Stock                  
Number of preferred shares authorized       25,000,000us-gaap_PreferredStockSharesAuthorized
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredStockMember
         
Number of preferred shares of beneficial interest authorized (in dollars per share)       $ 0.01us-gaap_PreferredStockParOrStatedValuePerShare
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredStockMember
         
Common Shares                  
Net proceeds from issue of shares after underwriter discounts but before offering expenses           165,652,000us-gaap_StockIssuedDuringPeriodValueNewIssues
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredStockMember
     
Series H                  
Preferred Stock                  
Annual dividend yield               7.50%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesHPreferredStockMember
 
Preferred stock, redemption price per share               $ 25.00us-gaap_PreferredStockRedemptionPricePerShare
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesHPreferredStockMember
 
Stock redeemed or called during period value               50,000,000us-gaap_StockRedeemedOrCalledDuringPeriodValue
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesHPreferredStockMember
 
Issuance costs associated with redeemed preferred shares               1,800,000us-gaap_PreferredStockRedemptionPremium
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesHPreferredStockMember
 
Series K                  
Preferred Stock                  
Number of shares issued       531,667us-gaap_PreferredStockSharesIssued
/ us-gaap_StatementClassOfStockAxis
= us-gaap_RedeemableConvertiblePreferredStockMember
         
Aggregate liquidation preference       26,583,000us-gaap_PreferredStockLiquidationPreferenceValue
/ us-gaap_StatementClassOfStockAxis
= us-gaap_RedeemableConvertiblePreferredStockMember
         
Annual dividend yield       5.60%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= us-gaap_RedeemableConvertiblePreferredStockMember
         
Annual dividend per share (in dollars per share)       $ 2.80000us-gaap_PreferredStockDividendRatePerDollarAmount
/ us-gaap_StatementClassOfStockAxis
= us-gaap_RedeemableConvertiblePreferredStockMember
         
Number of common shares to be issued on conversion of each preferred share       0.8163us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion
/ us-gaap_StatementClassOfStockAxis
= us-gaap_RedeemableConvertiblePreferredStockMember
         
Series L Cumulative Preferred Stock                  
Preferred Stock                  
Number of shares issued       6,900,000us-gaap_PreferredStockSharesIssued
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesLCumulativePreferredStockMember
         
Aggregate liquidation preference       172,500,000us-gaap_PreferredStockLiquidationPreferenceValue
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesLCumulativePreferredStockMember
         
Annual dividend yield       7.375%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesLCumulativePreferredStockMember
         
Annual dividend per share (in dollars per share)       $ 1.84375us-gaap_PreferredStockDividendRatePerDollarAmount
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesLCumulativePreferredStockMember
         
Series J                  
Preferred Stock                  
Annual dividend yield                 7.625%us-gaap_PreferredStockDividendRatePercentage
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesJPreferredStockMember
Preferred stock, redemption price per share                 $ 25.00us-gaap_PreferredStockRedemptionPricePerShare
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesJPreferredStockMember
Stock redeemed or called during period value                 84,800,000us-gaap_StockRedeemedOrCalledDuringPeriodValue
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesJPreferredStockMember
Issuance costs associated with redeemed preferred shares                 2,900,000us-gaap_PreferredStockRedemptionPremium
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesJPreferredStockMember
Corporate Office Properties, L.P.                  
Preferred Stock                  
Number of shares issued       7,431,667us-gaap_PreferredStockSharesIssued
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
         
Aggregate liquidation preference       199,083,000us-gaap_PreferredStockLiquidationPreferenceValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
         
Stock redeemed or called during period value       50,000,000us-gaap_StockRedeemedOrCalledDuringPeriodValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
84,750,000us-gaap_StockRedeemedOrCalledDuringPeriodValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
55,000,000us-gaap_StockRedeemedOrCalledDuringPeriodValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Common Shares                  
Net proceeds from issue of shares after underwriter discounts but before offering expenses       148,666,000us-gaap_StockIssuedDuringPeriodValueNewIssues
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
117,961,000us-gaap_StockIssuedDuringPeriodValueNewIssues
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
       
Number of common shares for each converted common unit (in shares)       1ofc_OperatingPartnershipUnitConversionRateToShares
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
         
Number of operating partnerships units converted into common shares (in units)       140,149.000us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
311,343.000us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
       
Dividends declared per common share       $ 1.1us-gaap_CommonStockDividendsPerShareDeclared
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
$ 1.10us-gaap_CommonStockDividendsPerShareDeclared
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
$ 1.10us-gaap_CommonStockDividendsPerShareDeclared
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
     
Corporate Office Properties, L.P. | Common Stock Issued to Public Under At-the-Market Program                  
Common Shares                  
Shares issued to the public             1,500,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementEquityComponentsAxis
= ofc_CommonStockIssuedtoPublicUnderAttheMarketProgramMember
   
Net proceeds from issue of shares after underwriter discounts but before offering expenses             38,500,000us-gaap_StockIssuedDuringPeriodValueNewIssues
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementEquityComponentsAxis
= ofc_CommonStockIssuedtoPublicUnderAttheMarketProgramMember
   
Issuance of stock, weighted average price per share             $ 26.05ofc_IssuanceofStockWeightedAveragePricePerShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementEquityComponentsAxis
= ofc_CommonStockIssuedtoPublicUnderAttheMarketProgramMember
   
Payments of stock issuance costs             586,000us-gaap_PaymentsOfStockIssuanceCosts
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementEquityComponentsAxis
= ofc_CommonStockIssuedtoPublicUnderAttheMarketProgramMember
   
Corporate Office Properties, L.P. | Preferred Shares                  
Common Shares                  
Net proceeds from issue of shares after underwriter discounts but before offering expenses           165,652,000us-gaap_StockIssuedDuringPeriodValueNewIssues
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_PreferredStockMember
     
Corporate Office Properties, L.P. | Series H                  
Preferred Stock                  
Annual dividend yield               7.50%us-gaap_PreferredStockDividendRatePercentage
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesHPreferredStockMember
 
Preferred stock, redemption price per share               $ 25.00us-gaap_PreferredStockRedemptionPricePerShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesHPreferredStockMember
 
Stock redeemed or called during period value               50,000,000us-gaap_StockRedeemedOrCalledDuringPeriodValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesHPreferredStockMember
 
Issuance costs associated with redeemed preferred shares               1,800,000us-gaap_PreferredStockRedemptionPremium
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_SeriesHPreferredStockMember
 
Corporate Office Properties, L.P. | Series K                  
Preferred Stock                  
Number of shares issued       531,667us-gaap_PreferredStockSharesIssued
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_RedeemableConvertiblePreferredStockMember
         
Aggregate liquidation preference       26,583,000us-gaap_PreferredStockLiquidationPreferenceValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_RedeemableConvertiblePreferredStockMember
         
Annual dividend yield       5.60%us-gaap_PreferredStockDividendRatePercentage
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_RedeemableConvertiblePreferredStockMember
         
Annual dividend per share (in dollars per share)       $ 2.80000us-gaap_PreferredStockDividendRatePerDollarAmount
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_RedeemableConvertiblePreferredStockMember
         
Number of common shares to be issued on conversion of each preferred share       0.8163us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_RedeemableConvertiblePreferredStockMember
         
Corporate Office Properties, L.P. | Series L Cumulative Preferred Stock                  
Preferred Stock                  
Number of shares issued       6,900,000us-gaap_PreferredStockSharesIssued
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesLCumulativePreferredStockMember
         
Aggregate liquidation preference       172,500,000us-gaap_PreferredStockLiquidationPreferenceValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesLCumulativePreferredStockMember
         
Annual dividend yield       7.375%us-gaap_PreferredStockDividendRatePercentage
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesLCumulativePreferredStockMember
         
Annual dividend per share (in dollars per share)       $ 1.84375us-gaap_PreferredStockDividendRatePerDollarAmount
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesLCumulativePreferredStockMember
         
Corporate Office Properties, L.P. | Series J                  
Preferred Stock                  
Annual dividend yield                 7.625%us-gaap_PreferredStockDividendRatePercentage
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesJPreferredStockMember
Preferred stock, redemption price per share                 $ 25.00us-gaap_PreferredStockRedemptionPricePerShare
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesJPreferredStockMember
Stock redeemed or called during period value                 84,800,000us-gaap_StockRedeemedOrCalledDuringPeriodValue
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesJPreferredStockMember
Issuance costs associated with redeemed preferred shares                 $ 2,900,000us-gaap_PreferredStockRedemptionPremium
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ us-gaap_StatementClassOfStockAxis
= ofc_SeriesJPreferredStockMember