Annual report pursuant to Section 13 and 15(d)

Commitments And Contingencies (Tax Abatement Agreements) (Narrative) (Details)

v2.4.1.9
Commitments And Contingencies (Tax Abatement Agreements) (Narrative) (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Harborside Financial Center Plaza 4-A [Member]      
Commitments And Contingencies [Line Items]      
Project period 20 years    
Percentage of PILOT on project costs 2.00%cli_PaymentsInLieuOfPropertyTaxAsPercentageOfTotalProjectCost
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_HarborsideFinancialCenterPlazaFouraMember 		   
Total project costs $ 49,500,000cli_EstimatedCostOfProject
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_HarborsideFinancialCenterPlazaFouraMember 		   
Payments in lieu of property taxes (PILOT) 990,000cli_PaymentsInLieuOfPropertyTaxes
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_HarborsideFinancialCenterPlazaFouraMember 		   
Harborside Financial Center Plaza 5 [Member]      
Commitments And Contingencies [Line Items]      
Project period 20 years    
Percentage of PILOT on project costs 2.00%cli_PaymentsInLieuOfPropertyTaxAsPercentageOfTotalProjectCost
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_HarborsideFinancialCenterPlazaFiveMember 		   
Total project costs 170,900,000cli_EstimatedCostOfProject
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_HarborsideFinancialCenterPlazaFiveMember 		   
Payments in lieu of property taxes (PILOT) $ 3,400,000cli_PaymentsInLieuOfPropertyTaxes
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_HarborsideFinancialCenterPlazaFiveMember 		$ 3,400,000cli_PaymentsInLieuOfPropertyTaxes
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_HarborsideFinancialCenterPlazaFiveMember 		$ 3,400,000cli_PaymentsInLieuOfPropertyTaxes
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_HarborsideFinancialCenterPlazaFiveMember
Port Imperial 4/5 Garage [Member]      
Commitments And Contingencies [Line Items]      
Project period 5 years    
Period of real estate taxes phase in 5 years    
Park Square [Member]      
Commitments And Contingencies [Line Items]      
Period of partial abatement of real estate taxes 4 years