Quarterly report pursuant to Section 13 or 15(d)

Investments In Unconsolidated Joint Ventures (Narrative) (Details)

v2.4.1.9
Investments In Unconsolidated Joint Ventures (Narrative) (Details) (USD $)
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]      
Investments in unconsolidated joint ventures $ 262,052,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures   $ 247,468,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
Amount outstanding 42,000,000us-gaap_LineOfCredit   0us-gaap_LineOfCredit
Management, leasing, development and other services fees 1,600,000cli_ManagementLeasingDevelopmentAndOtherServicesFees 504,000cli_ManagementLeasingDevelopmentAndOtherServicesFees  
Accounts receivable due from unconsolidated joint ventures 1,200,000us-gaap_DueFromJointVentures   1,000,000us-gaap_DueFromJointVentures
Maximum exposure to loss 206,400,000us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount    
Estimated future funding commitments 76,600,000cli_VariableInterestEntityEntityEstimatedFutureFundingCommitments    
Unconsolidated Joint Venture Office Buildings [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of properties 36us-gaap_NumberOfRealEstateProperties
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVentureOfficeBuildingsMember 		   
Unconsolidated Joint Venture Office And Retail Buildings [Member]      
Schedule of Equity Method Investments [Line Items]      
Area of property (in square feet) 5,700,000us-gaap_AreaOfRealEstateProperty
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVentureOfficeAndRetailBuildingsMember 		   
Unconsolidated Joint Venture Retail Buildings [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of properties 2us-gaap_NumberOfRealEstateProperties
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVentureRetailBuildingsMember 		   
Unconsolidated Joint Venture Multi-Family Properties [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of properties 14us-gaap_NumberOfRealEstateProperties
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVentureMultipleFamilyPropertiesMember 		   
Number of units 4,560us-gaap_NumberOfUnitsInRealEstateProperty
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVentureMultipleFamilyPropertiesMember 		   
Unconsolidated Joint Venture Hotel [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of units 350us-gaap_NumberOfUnitsInRealEstateProperty
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVentureHotelMember 		   
Unconsolidated Joint Venture Development Projects [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of units 1,354us-gaap_NumberOfUnitsInRealEstateProperty
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVentureDevelopmentProjectsMember 		   
Unconsolidated Joint Venture Land Parcels [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of units 2,853us-gaap_NumberOfUnitsInRealEstateProperty
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVentureLandParcelsMember 		   
Unconsolidated Joint Ventures [Member] | Guarantee of Indebtedness of Others [Member]      
Schedule of Equity Method Investments [Line Items]      
Maximum borrowing capacity 477,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_LossContingenciesByNatureOfContingencyAxis
= us-gaap_GuaranteeOfIndebtednessOfOthersMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVenturesMember 		   
Amount outstanding 250,700,000us-gaap_LineOfCredit
/ us-gaap_LossContingenciesByNatureOfContingencyAxis
= us-gaap_GuaranteeOfIndebtednessOfOthersMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVenturesMember 		   
Unconsolidated Joint Ventures [Member] | Parent Company [Member] | Guarantee of Indebtedness of Others [Member]      
Schedule of Equity Method Investments [Line Items]      
Maximum borrowing capacity 82,800,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
/ us-gaap_LossContingenciesByNatureOfContingencyAxis
= us-gaap_GuaranteeOfIndebtednessOfOthersMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVenturesMember 		   
Amount outstanding 51,900,000us-gaap_LineOfCredit
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
/ us-gaap_LossContingenciesByNatureOfContingencyAxis
= us-gaap_GuaranteeOfIndebtednessOfOthersMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVenturesMember 		   
Minimum [Member]      
Schedule of Equity Method Investments [Line Items]      
Percentage of interest in venture 7.50%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_RangeAxis
= us-gaap_MinimumMember 		   
Maximum [Member]      
Schedule of Equity Method Investments [Line Items]      
Percentage of interest in venture 85.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_RangeAxis
= us-gaap_MaximumMember 		   
Variable Interest Entity [Member]      
Schedule of Equity Method Investments [Line Items]      
Investments in unconsolidated joint ventures 129,800,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
/ us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis
= us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember 		   
Number of VIEs 9cli_NumberOfVariableInterestEntities
/ us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis
= us-gaap_VariableInterestEntityNotPrimaryBeneficiaryMember 		   
Office [Member] | Unconsolidated Joint Venture Land Parcels [Member]      
Schedule of Equity Method Investments [Line Items]      
Area of property (in square feet) 1,400,000us-gaap_AreaOfRealEstateProperty
/ us-gaap_MajorPropertyClassAxis
= us-gaap_OfficeBuildingMember
/ us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis
= cli_UnconsolidatedJointVentureLandParcelsMember 		   
South Pier At Harborside [Member]      
Schedule of Equity Method Investments [Line Items]      
Investments in unconsolidated joint ventures    [1]    
Number of units 350us-gaap_NumberOfUnitsInRealEstateProperty
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= cli_SouthPierAtHarborsideMember 		   
Percentage of interest in venture 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= cli_SouthPierAtHarborsideMember 		[2]    
Letter of credit $ 4,100,000cli_LineOfCreditFacilityInSupportOfDebtInstrumentFairValueOfAmountOutstanding
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= cli_SouthPierAtHarborsideMember 		   
[1] The negative carrying amount for this venture of $1,937 and $1,854 as of March 31, 2015 and December 31, 2014, respectively, were included in accounts payable, accrued expenses and other liabilities.
[2] Company's effective ownership % represents the Company's entitlement to residual distributions after payments of priority returns, where applicable.