Annual report pursuant to Section 13 and 15(d)

Investments In Unconsolidated Joint Ventures (KPG-P 100 IMW JV, LLC) (Details)

v2.4.1.9
Investments In Unconsolidated Joint Ventures (KPG-P 100 IMW JV, LLC) (Details) (USD $)
 12 Months Ended 0 Months Ended
Dec. 31, 2014
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Dec. 09, 2013
Dec. 31, 2013
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Schedule of Equity Method Investments [Line Items]      
Percentage of interest in venture    [1]    
Number of parking spaces 110cli_NumberOfParkingSpaces   850cli_NumberOfParkingSpaces
Mortgage loans, carrying amount $ 1,673,364,000us-gaap_MortgageLoansOnRealEstateCarryingAmountOfMortgages    
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 		   
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 		   
KPG-IMW Owner, LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Percentage of interest in venture   33.33%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ dei_LegalEntityAxis
= cli_KpgImwOwnerLlcMember 		 
Mortgage loans, carrying amount 61,500,000us-gaap_MortgageLoansOnRealEstateCarryingAmountOfMortgages
/ dei_LegalEntityAxis
= cli_KpgImwOwnerLlcMember 		   
Interest rate 7.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ dei_LegalEntityAxis
= cli_KpgImwOwnerLlcMember 		   
Number of extension options 2cli_DebtInstrumentNumberOfExtensionOptions
/ dei_LegalEntityAxis
= cli_KpgImwOwnerLlcMember 		   
Credit facility, extension period 1 year    
Construction reserve 25,000,000cli_LineOfCreditFacilityConstructionReserve
/ dei_LegalEntityAxis
= cli_KpgImwOwnerLlcMember 		   
Construction reserve, amount outstanding 15,800,000cli_LineOfCreditFacilityConstructionReserveAmountOutstanding
/ dei_LegalEntityAxis
= cli_KpgImwOwnerLlcMember 		   
KPG-MCG IMW, LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Percentage of interest in venture 57.7677%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ dei_LegalEntityAxis
= cli_KpgMcgImwLlcMember 		   
KPG-P [Member]      
Schedule of Equity Method Investments [Line Items]      
Holding and distribution pattern under operating agreement In general, the operating agreement of KPG-P provides that net operating cash flows are distributed first, to the members in proportion to their unreturned capital contributions, until each member's unreturned capital contributions have been reduced to zero; and, thereafter, to the members, in accordance with their percentage interests. Net cash flows from a capital event are distributed first, to the members in proportion to the members' unreturned capital contributions, until each member's unreturned capital contributions have been reduced to zero; second, to the members in proportion to the members' unreturned deferred capital contributions, until each member's deferred unreturned capital contributions have been reduced to zero; and, thereafter, to the members in accordance with their percentage interests.    
KPG-P 100 IMW JV, LLC [Member]      
Schedule of Equity Method Investments [Line Items]      
Percentage of interest in venture 33.33%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= cli_KpgPOneHundredImwJvLlcMember 		[1]    
Area of property (in square feet) 339,615us-gaap_AreaOfRealEstateProperty
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= cli_KpgPOneHundredImwJvLlcMember 		   
Business acquisition, cash paid   2,800,000us-gaap_PaymentsToAcquireBusinessesGross
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= cli_KpgPOneHundredImwJvLlcMember 		 
Mortgage loans, carrying amount 61,500,000us-gaap_MortgageLoansOnRealEstateCarryingAmountOfMortgages
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= cli_KpgPOneHundredImwJvLlcMember 		   
Mortgage loan, maturity date 09/09/16    
Number of extension options 2cli_DebtInstrumentNumberOfExtensionOptions
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= cli_KpgPOneHundredImwJvLlcMember 		   
Construction reserve 25,000,000cli_LineOfCreditFacilityConstructionReserve
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= cli_KpgPOneHundredImwJvLlcMember 		   
100 IMW Property [Member]      
Schedule of Equity Method Investments [Line Items]      
Number of stories   9cli_NumberOfStoriesInRealEstateProperty
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_OneHundredImwPropertyMember 		 
Area of property (in square feet) 55,000us-gaap_AreaOfRealEstateProperty
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_OneHundredImwPropertyMember 		400,000us-gaap_AreaOfRealEstateProperty
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_OneHundredImwPropertyMember 		 
Business acquisition, cash paid   40,500,000us-gaap_PaymentsToAcquireBusinessesGross
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_OneHundredImwPropertyMember 		 
100 IMW Property [Member] | Minimum [Member]      
Schedule of Equity Method Investments [Line Items]      
Total project costs $ 20,000,000cli_EstimatedCostOfProject
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= cli_OneHundredImwPropertyMember 		   
KPG-MCG's Interest In KPG-P [Member]      
Schedule of Equity Method Investments [Line Items]      
Investment ownership percentage 57.7024%cli_InvestmentOwnershipPercentage
/ cli_InvestmentsInUnconsolidatedJointVentuesByNameAxis
= cli_KpgMcgsInterestInKpgPMember 		   
KPG's Interest In KPG-P [Member]      
Schedule of Equity Method Investments [Line Items]      
Investment ownership percentage 17.8928%cli_InvestmentOwnershipPercentage
/ cli_InvestmentsInUnconsolidatedJointVentuesByNameAxis
= cli_KpgsInterestInKpgPMember 		   
Parkway's Interest In KPG-P [Member]      
Schedule of Equity Method Investments [Line Items]      
Investment ownership percentage 24.4048%cli_InvestmentOwnershipPercentage
/ cli_InvestmentsInUnconsolidatedJointVentuesByNameAxis
= cli_ParkwaysInterestInKpgPMember 		   
[1] Company's effective ownership % represents the Company's entitlement to residual distributions after payments of priority returns, where applicable.