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Share-Based Compensation and Benefit Plans (Narrative) (Details) (USD $) | 12 Months Ended | 3 Months Ended
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Jun. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period | 375,316 us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised | 183,871 us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised | 468,839 us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised |
Total compensation cost for option and share awards | $ 16,000,000 cpt_ShareBasedCompensationArrangementByShareBasedPaymentAwardCompensationCostForPeriod | $ 14,700,000 cpt_ShareBasedCompensationArrangementByShareBasedPaymentAwardCompensationCostForPeriod | $ 13,700,000 cpt_ShareBasedCompensationArrangementByShareBasedPaymentAwardCompensationCostForPeriod |
Document Fiscal Year Focus | 2014 |  |  |
Total capitalized compensation cost for option and share awards | 2,700,000 us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount | 2,200,000 us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount | 1,400,000 us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount |
Percentage Of Market Value Per Share At Which Shares Purchased Under Employee Share Purchase Plan | 85.00%cpt_PercentageOfMarketValueatWhichSharesPurchasedUnderEmployeeSharePurchasePlan |  |  |
Employee Share Purchase Plan, Maximum Authorized Amount Per Participant | 25,000 cpt_EmployeeSharePurchasePlanMaximumAuthorizedAmountPerParticipant |  |  |
Share Awards Held In Employee Trust Shares | 1,800,000 cpt_ShareAwardsHeldInEmployeeTrustShares | 1,900,000 cpt_ShareAwardsHeldInEmployeeTrustShares |  |
Share Awards Held In Non Qualified Deferred Compensation Plan Shares | 43,700,000 cpt_TradingSecuritiesHeldInEmployeeTrustValue | 41,300,000 cpt_TradingSecuritiesHeldInEmployeeTrustValue |  |
Cash Required By Plan Participants Upon Withdrawal | 24,700,000 cpt_CashRequiredByPlanParticipantsUponWithdrawal | 25,400,000 cpt_CashRequiredByPlanParticipantsUponWithdrawal |  |
Granted, Options Outstanding | 84,452 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross |
Share Awards Held In Non Qualified Deferred Compensation Plan Shares | 1,200,000 cpt_ShareAwardsHeldInNonQualifiedDeferredCompensationPlanShares | 1,200,000 cpt_ShareAwardsHeldInNonQualifiedDeferredCompensationPlanShares |  |
Trading Securities Held In Non Qualified Deferred Compensation Plan Value | 27,700,000 cpt_TradingSecuritiesHeldInNonQualifiedDeferredCompensationPlanValue | 18,100,000 cpt_TradingSecuritiesHeldInNonQualifiedDeferredCompensationPlanValue |  |
Defined Contribution Plan, Cost Recognized | 2,200,000 us-gaap_DefinedContributionPlanCostRecognized | 2,200,000 us-gaap_DefinedContributionPlanCostRecognized | 2,200,000 us-gaap_DefinedContributionPlanCostRecognized |
Options [Member] |  |  |  |
Allocated Share-based Compensation Expense | 300,000 us-gaap_AllocatedShareBasedCompensationExpense / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period | 400,000 us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | 200,000 us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |  |
Total intrinsic value of options exercised during the period | 7,400,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | 5,300,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | 12,200,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember |
Remaining weighted average contractual life (years) outstanding options | 4 years 1 month 5 days |  |  |
Remaining weighted average contractual life (years) exercisable options | 4 years 1 month 5 days |  |  |
Share Awards and Vesting [Member] |  |  |  |
Total unrecognized compensation cost related to unvested options which is expected to be amortized | 35,700,000 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / us-gaap_AwardTypeAxis = cpt_ShareAwardsAndVestingMember |  |  |
Fair value of shares vested | $ 17,100,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = cpt_ShareAwardsAndVestingMember | $ 15,900,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = cpt_ShareAwardsAndVestingMember | $ 13,900,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodTotalFairValue / us-gaap_AwardTypeAxis = cpt_ShareAwardsAndVestingMember |
Minimum [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | 20.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |
Minimum [Member] | Options [Member] |  |  |  |
Vesting period, years | 3 years |  |  |
Minimum [Member] | Share Awards and Vesting [Member] |  |  |  |
Vesting period, years | 3 years |  |  |
Maximum [Member] |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage | 33.33%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |
Maximum [Member] | Options [Member] |  |  |  |
Vesting period, years | 5 years |  |  |
Maximum [Member] | Share Awards and Vesting [Member] |  |  |  |
Vesting period, years | 5 years |  |  |
2011 Share Incentive Plan [Member] |  |  |  |
Total fungible units to be issued | 5,500,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant / us-gaap_PlanNameAxis = cpt_TwoThousandElevenShareIncentivePlanMember |  |  | 9,100,000 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant / us-gaap_PlanNameAxis = cpt_TwoThousandElevenShareIncentivePlanMember
Units available under the 2011 Share Plan |  |  |  | 5,800,000 cpt_NumberOfFungibleUnitAuthorizedToIssueUnderShareBasedCompensationPlan / us-gaap_PlanNameAxis = cpt_TwoThousandElevenShareIncentivePlanMember
Fungible units transferred from the 2002 Share Plan to the 2011 Share Plan |  |  |  | 3,300,000 cpt_NumberOfFungibleUnitAuthorizedToIssueUnderShareBasedCompensationPlans / us-gaap_PlanNameAxis = cpt_TwoThousandElevenShareIncentivePlanMember
Fungible Units To Full Value Award Conversion Ratio |  |  |  | 3.45 cpt_FungibleUnitsToFullValueAwardConversionRatio / us-gaap_PlanNameAxis = cpt_TwoThousandElevenShareIncentivePlanMember
Full Value award in the fungible unit conversion ratio |  |  |  | 1.0 cpt_FullValueawardinthefungibleunitconversionratio / us-gaap_PlanNameAxis = cpt_TwoThousandElevenShareIncentivePlanMember
Expiration value of option right or other award |  |  |  | 0.83 cpt_ExpirationValueOfOptionRightOrOtherAward / us-gaap_PlanNameAxis = cpt_TwoThousandElevenShareIncentivePlanMember
Common shares which could be granted pursuant to full value awards | 1,600,000 cpt_CommonSharesWhichCouldBeGrantedPursuantToFullValueAwards / us-gaap_PlanNameAxis = cpt_TwoThousandElevenShareIncentivePlanMember |  |  |

X
- Definition Cash required to be paid to us by plan participants upon the withdrawal of any assets from the trust and is included in accounts receivable - affiliates in our consolidated financial statements. + References No definition available. + Details
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- Definition Common shares which could be granted pursuant to full value awards based on the 3.45 to 1.0 fungible unit-to-full value award conversion ratio. + References No definition available. + Details
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- Definition Maximum authorized purchase amount of shares during any plan year per participant for our employee share purchase plan. + References No definition available. + Details
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- Definition An option, right, or other award which does not deliver the full value at date of grant and expires five years or less from the date of grant counts against the Fungible Pool Limit as this portion of a fungible pool unit + References No definition available. + Details
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- Definition The full value award in the fungible unit to full value award conversion ratio regarding the shares from the 2002 share incentive plan transferred into the 2011 share incentive plan. + References No definition available. + Details
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- Definition The award conversion ratio regarding the shares from the 2002 share incentive plan transferred into the 2011 share incentive plan. + References No definition available. + Details
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- Definition Shares reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable, specifically for the 2011 Share Plan, which superseded the 2002 Share Plan. + References No definition available. + Details
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- Definition Shares reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable, specifically from the 2002 Share Plan, which has been superseded by the 2011 Share Plan. + References No definition available. + Details
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- Definition The percentage of market value per share at which shares may be purchased under our employee share purchase plan. + References No definition available. + Details
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- Definition The total amount of share awards held in a Rabbi Trust. + References No definition available. + Details
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- Definition The total amount of share awards held in a non-qualified deferred compensation plan. + References No definition available. + Details
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- Definition Equity-based compensation cost during the period with respect to the award, which was recognized in income. + References No definition available. + Details
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- Definition Market value of trading securities held in a rabbi trust. + References No definition available. + Details
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- Definition Market value of trading securities held in a non-qualified deferred compensation plan. + References No definition available. + Details
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- Definition This is focus fiscal year of the document report in CCYY format. For a 2006 annual report, which may also provide financial information from prior periods, fiscal 2006 should be given as the fiscal year focus. Example: 2006. + References No definition available. + Details
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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F + Details
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- Definition The amount of the cost recognized during the period for defined contribution plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942 + Details
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- Definition Represents the compensation cost capitalized during the period arising from equity-based compensation arrangements (for example, shares of stock, units, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Percentage of vesting of share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Gross number of share options (or share units) granted during the period. + References No definition available. + Details
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- Definition Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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