Annual report pursuant to Section 13 and 15(d)

Commitments And Contingencies (Departure Of Executive Officers) (Narrative) (Details)

v2.4.1.9
Commitments And Contingencies (Departure Of Executive Officers) (Narrative) (Details) (USD $)
 12 Months Ended 6 Months Ended 0 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Sep. 30, 2014
May 11, 2015
Commitments And Contingencies [Line Items]          
Severance benefits $ 23,800,000us-gaap_SeveranceCosts1        
Restricted stock units vested 183,214us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod 149,463us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod 123,877us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod    
Accounts payable, accrued expenses and other liabilities 126,971,000us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent 121,286,000us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent      
Employee Severance [Member]          
Commitments And Contingencies [Line Items]          
Accounts payable, accrued expenses and other liabilities 11,600,000us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent
/ us-gaap_RestructuringCostAndReserveAxis
= us-gaap_EmployeeSeveranceMember 		       
Messr Lefkowitz [Member]          
Commitments And Contingencies [Line Items]          
Severance benefits 3,400,000us-gaap_SeveranceCosts1
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurLefkowitzMember 		       
Stock options vested 11,457us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurLefkowitzMember 		       
Restricted stock units vested 68,667us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurLefkowitzMember 		       
Period for continuation of health insurance 48 months        
Messr Thomas [Member]          
Commitments And Contingencies [Line Items]          
Severance benefits 3,100,000us-gaap_SeveranceCosts1
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurThomasMember 		       
Stock options vested 33,605us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurThomasMember 		       
Restricted stock units vested 41,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurThomasMember 		       
Period for continuation of health insurance 48 months        
Consulting payment       300,000us-gaap_ProfessionalFees
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurThomasMember 		 
Scenario, Forecast [Member]          
Commitments And Contingencies [Line Items]          
Restricted stock units vested         84,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
Scenario, Forecast [Member] | Messr Hersh [Member]          
Commitments And Contingencies [Line Items]          
Severance benefits         8,000,000us-gaap_SeveranceCosts1
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurHershMember
Restricted stock units vested         210,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurHershMember
Period for continuation of health insurance         48 months
Cash payment         504,000cli_EmployeeTerminationAgreementCashPayment
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurHershMember
Termination payment multiplier         210,000cli_EmployeeTerminationAgreementMultiplier
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurHershMember
Shares issued         41,811us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurHershMember
Deferred retirement compensation contribution         2,311,792cli_EmployeeTerminationAgreementDeferredRetirementCompensationContribution
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
/ us-gaap_TitleOfIndividualAxis
= cli_MessieurHershMember
Total Stockholder Return Based Awards [Member]          
Commitments And Contingencies [Line Items]          
Restricted stock units vested 357us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= cli_TotalStockholderReturnBasedAwardsMember 		       
Shares issued 45,062us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross
/ us-gaap_AwardTypeAxis
= cli_TotalStockholderReturnBasedAwardsMember 		       
Total Stockholder Return Based Awards [Member] | Scenario, Forecast [Member]          
Commitments And Contingencies [Line Items]          
Restricted stock units vested         675us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_AwardTypeAxis
= cli_TotalStockholderReturnBasedAwardsMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
Shares issued         41,811us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross
/ us-gaap_AwardTypeAxis
= cli_TotalStockholderReturnBasedAwardsMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember