Annual report pursuant to Section 13 and 15(d)

Unsecured Revolving Credit Facility (Narrative) (Details)

v2.4.1.9
Unsecured Revolving Credit Facility (Narrative) (Details) (USD $)
12 Months Ended 0 Months Ended
Dec. 31, 2014
item
entity
Jul. 15, 2013
Unsecured Revolving Credit Facility [Member]    
Line of Credit Facility [Line Items]    
Number of lending institutions 17cli_LineOfCreditFacilityLendingInstitutionsNumber
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
 
Borrowing capacity under the credit facility $ 600,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
 
Expandable borrowing capacity under the credit facility 1,000,000,000cli_LineOfCreditFacilityExpandableMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
 
Credit facility maturity date Jul. 01, 2017  
Number of extension options 2cli_DebtInstrumentNumberOfExtensionOptions
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
 
Credit facility, extension period 6 months  
Line of credit facility, bid feature, current borrowing capacity 300,000,000cli_LineOfCreditFacilityBidFeatureCurrentBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
 
Terms of the unsecured facility The terms of the unsecured facility include certain restrictions and covenants which limit, among other things the incurrence of additional indebtedness, the incurrence of liens and the disposition of real estate properties (to the extent that: (i) such property dispositions cause the Company to default on any of the financial ratios of the facility described below, or (ii) the property dispositions are completed while the Company is under an event of default under the facility, unless, under certain circumstances, such disposition is being carried out to cure such default), and which require compliance with financial ratios relating to the maximum leverage ratio (60 percent), the maximum amount of secured indebtedness (40 percent), the minimum amount of fixed charge coverage (1.5 times), the maximum amount of unsecured indebtedness (60 percent), the minimum amount of unencumbered property interest coverage (2.0 times) and certain investment limitations (generally 15 percent of total capitalization).  
Terms of dividend restriction If an event of default has occurred and is continuing, the Company will not make any excess distributions except to enable the Company to continue to qualify as a REIT under the Code. The Company was in compliance with its debt covenants as of December 31, 2014.  
Unsecured Revolving Credit Facility Extension 1 [Member]    
Line of Credit Facility [Line Items]    
Credit facility extension fee, basis points 0.075%cli_LineOfCreditFacilityBasisPointFacilityFee
/ us-gaap_CreditFacilityAxis
= cli_UnsecuredRevolvingCreditFacilityExtensionOneMember
 
Unsecured Revolving Credit Facility Extension 2 [Member]    
Line of Credit Facility [Line Items]    
Credit facility extension fee, basis points 0.075%cli_LineOfCreditFacilityBasisPointFacilityFee
/ us-gaap_CreditFacilityAxis
= cli_UnsecuredRevolvingCreditFacilityExtensionTwoMember
 
Previous Unsecured Revolving Credit Facility [Member]    
Line of Credit Facility [Line Items]    
Borrowing capacity under the credit facility   $ 600,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= cli_PreviousUnsecuredRevolvingCreditFacilityMember
Credit facility extension fee, basis points   0.25%cli_LineOfCreditFacilityBasisPointFacilityFee
/ us-gaap_CreditFacilityAxis
= cli_PreviousUnsecuredRevolvingCreditFacilityMember
Property Debt, Interest Rate, Spread Over LIBOR   1.25%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= cli_PreviousUnsecuredRevolvingCreditFacilityMember
Minimum [Member] | Unsecured Revolving Credit Facility [Member]    
Line of Credit Facility [Line Items]    
Fixed charge coverage ratio 1.5cli_DebtInstrumentCovenantComplianceFixedChargeCoverage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
Unencumbered property interest coverage 2.0cli_DebtInstrumentCovenantComplianceUnencumberedPropertyInterestCoverage
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
 
Maximum [Member] | Unsecured Revolving Credit Facility [Member]    
Line of Credit Facility [Line Items]    
Leverage ratio 60.00%cli_DebtInstrumentCovenantComplianceLeverageRatio
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Secured indebtedness 40.00%cli_DebtInstrumentCovenantComplianceSecuredIndebtedness
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Unsecured indebtedness 60.00%cli_DebtInstrumentCovenantComplianceUnsecuredIndebtedness
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
 
Investment limitations as a percentage of total capitalization 15.00%cli_DebtInstrumentCovenantComplianceInvestmentLimitationsAsPercentageOfTotalCapitalization
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember