Annual report pursuant to Section 13 and 15(d)

Real Estate Transactions (Schedule Of Properties Which Commenced Initial Operations) (Details)

v2.4.1.9
Real Estate Transactions (Schedule Of Properties Which Commenced Initial Operations) (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2013
item
sqft
Dec. 31, 2014
item
Real Estate Properties [Line Items]    
Number of Buildings 2cli_NumberOfBuildingsOnPropertiesCommencingInitialOperations  
Rentable Square Feet 220,242cli_AreaOfRealEstatePropertyCommencingInitialOperations  
Garage Parking Spaces 850cli_NumberOfParkingSpaces 110cli_NumberOfParkingSpaces
Development Costs Incurred by Company $ 102,267cli_RealEstateDevelopmentCostsIncurred  
14 Sylvan Way [Member]    
Real Estate Properties [Line Items]    
Number of Buildings 1cli_NumberOfBuildingsOnPropertiesCommencingInitialOperations
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_FourteenSylvanWayMember 		 
Rentable Square Feet 203,506cli_AreaOfRealEstatePropertyCommencingInitialOperations
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_FourteenSylvanWayMember 		 
Development Costs Incurred by Company 51,611cli_RealEstateDevelopmentCostsIncurred
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_FourteenSylvanWayMember 		[1]  
Development Costs Per Square Foot 254cli_DevelopmentCostsPerSquareFoot
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_FourteenSylvanWayMember 		 
14 Sylvan Way [Member] | Leases [Member]    
Real Estate Properties [Line Items]    
Development Costs Incurred by Company 4,300cli_RealEstateDevelopmentCostsIncurred
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_LeaseAgreementsMember
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_FourteenSylvanWayMember 		 
Port Imperial South 4/5 [Member]    
Real Estate Properties [Line Items]    
Number of Buildings 1cli_NumberOfBuildingsOnPropertiesCommencingInitialOperations
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_PortImperialSouthFourAndFiveMember 		 
Rentable Square Feet 16,736cli_AreaOfRealEstatePropertyCommencingInitialOperations
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_PortImperialSouthFourAndFiveMember 		 
Garage Parking Spaces 850cli_NumberOfParkingSpaces
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_PortImperialSouthFourAndFiveMember 		 
Development Costs Incurred by Company 50,656cli_RealEstateDevelopmentCostsIncurred
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_PortImperialSouthFourAndFiveMember 		[2]  
Land [Member] | 14 Sylvan Way [Member]    
Real Estate Properties [Line Items]    
Development Costs Incurred by Company 13,000cli_RealEstateDevelopmentCostsIncurred
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_LandMember
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_FourteenSylvanWayMember 		 
Land [Member] | Port Imperial South 4/5 [Member]    
Real Estate Properties [Line Items]    
Development Costs Incurred by Company $ 13,100cli_RealEstateDevelopmentCostsIncurred
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_LandMember
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_PortImperialSouthFourAndFiveMember 		 
[1] Development costs included approximately $13.0 million in land costs and $4.3 million in leasing costs. Amounts are as of December 31, 2013.
[2] Development costs included approximately $13.1 million in land costs. Amounts are as of December 31, 2013.