Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation (Details)

v2.4.1.9
Share-Based Compensation (Details) (USD $)
3 Months Ended 0 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 05, 2015
Options      
Exercised (in shares) 70,374us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised 26,614us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised  
Performance share units      
Assumptions used to value stock awards      
Weighted average grant date fair value (in dollars per share) 36.76us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
   
Baseline value per common share (in dollars per share) 29.28ofc_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsBaselineCommonShareValue
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
   
Expected volatility of common shares (as a percent) 19.90%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
   
Risk-free interest rate (as a percent) 0.99%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
   
Restricted shares      
Share-Based Compensation      
Stock awards granted (in shares or units) 177,674us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= ofc_RestrictedSharesMember
   
Aggregate grant date fair value 5,200,000ofc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodAggregateFairValue
/ us-gaap_AwardTypeAxis
= ofc_RestrictedSharesMember
   
Assumptions used to value stock awards      
Weighted average grant date fair value (in dollars per share) 29.46us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= ofc_RestrictedSharesMember
   
Other Share-based Compensation Additional Disclosures      
Shares vested (in shares) 127,444us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= ofc_RestrictedSharesMember
   
Weighted average fair value of shares vested (in dollars per share) 26.01us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= ofc_RestrictedSharesMember
   
Aggregate intrinsic value of restricted common shares, forfeiture restrictions lapsed 3,700,000ofc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= ofc_RestrictedSharesMember
   
Options      
Options      
Exercised (in shares) 70,374us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_AwardTypeAxis
= us-gaap_StockOptionMember
   
Weighted average exercise price (in dollars per share) 26.23us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_AwardTypeAxis
= us-gaap_StockOptionMember
   
Aggregate intrinsic value of options exercised (in dollars) 291,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_StockOptionMember
   
2014 PSU Grants | Performance share units      
Share-Based Compensation      
Stock awards granted (in shares or units)     45,656us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
/ us-gaap_PlanNameAxis
= ofc_A2014PSUGrantsMember
Aggregate grant date fair value     $ 1,700,000ofc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodAggregateFairValue
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
/ us-gaap_PlanNameAxis
= ofc_A2014PSUGrantsMember
Potential earned PSUs payout for defined levels of performance under awards      
Earned PSUs payout (as a percent of PSUs granted) on 75th or greater percentile rank 200.00%ofc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfEarnedPerformanceShareUnitsPayoutPercentageBasedOnPercentileRankGreaterThanOrEqualsTo75
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
/ us-gaap_PlanNameAxis
= ofc_A2014PSUGrantsMember
   
Earned PSUs payout (as a percent of PSUs granted) on 50th percentile rank 100.00%ofc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfEarnedPerformanceShareUnitsPayoutPercentageBasedOnPercentileRankEqualsTo50
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
/ us-gaap_PlanNameAxis
= ofc_A2014PSUGrantsMember
   
Earned PSUs payout (as a percent of PSUs granted) on 25th percentile rank 50.00%ofc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfEarnedPerformanceShareUnitsPayoutPercentageBasedOnPercentileRankEqualsTo25
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
/ us-gaap_PlanNameAxis
= ofc_A2014PSUGrantsMember
   
Performance share units granted on percentile rank below 25th (as a percent) 0.00%ofc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfEarnedPerformanceShareUnitsPayoutPercentageBasedOnPercentileRankLessThan25
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
/ us-gaap_PlanNameAxis
= ofc_A2014PSUGrantsMember
   
The number of percentile ranks to fall between to earn interpolated PSUs between such percentile ranks, conditioned on the percentile rank exceeding 25% 2ofc_NumberOfPercentileRanksToFallBetweenToEarnInterpolatedPsu
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
/ us-gaap_PlanNameAxis
= ofc_A2014PSUGrantsMember
   
A2012PSUGrants [Member] | Performance share units      
Assumptions used to value stock awards      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Shares issued for Awards Vested in Period     40,309ofc_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsSharesissuedforAwardsVestedinPeriod
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
/ us-gaap_PlanNameAxis
= ofc_A2012PSUGrantsMember
2013 PSU Grants [Member] | Performance share units | Former Chief Financial Officer [Member]      
Assumptions used to value stock awards      
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Shares issued for Awards Vested in Period     15,289ofc_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherthanOptionsSharesissuedforAwardsVestedinPeriod
/ us-gaap_AwardTypeAxis
= ofc_PerformanceShareUnitsMember
/ us-gaap_PlanNameAxis
= ofc_A2013PSUGrantsMember
/ us-gaap_TitleOfIndividualAxis
= ofc_FormerChiefFinancialOfficerMember