Quarterly report pursuant to Section 13 or 15(d)

Senior Unsecured Notes (Summary Of Senior Unsecured Notes) (Details)

v2.4.1.9
Senior Unsecured Notes (Summary Of Senior Unsecured Notes) (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Debt Instrument [Line Items]    
Senior Unsecured Notes $ 1,268,018us-gaap_UnsecuredDebt $ 1,267,744us-gaap_UnsecuredDebt
5.800% Senior Unsecured Notes, Due January 15, 2016 [Member]    
Debt Instrument [Line Items]    
Senior Unsecured Notes 200,066us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= cli_FivePointEightZeroZeroPercentSeniorUnsecuredNotesDueJanuaryFifteenTwoThousandSixteenMember 		200,086us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= cli_FivePointEightZeroZeroPercentSeniorUnsecuredNotesDueJanuaryFifteenTwoThousandSixteenMember
Effective Rate 5.806%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_LongtermDebtTypeAxis
= cli_FivePointEightZeroZeroPercentSeniorUnsecuredNotesDueJanuaryFifteenTwoThousandSixteenMember 		[1]  
Interest rate of senior unsecured notes 5.80%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= cli_FivePointEightZeroZeroPercentSeniorUnsecuredNotesDueJanuaryFifteenTwoThousandSixteenMember 		 
Maturity date of the senior unsecured notes Jan. 15, 2016  
2.500% Senior Unsecured Notes Due December 15, 2017 [Member]    
Debt Instrument [Line Items]    
Senior Unsecured Notes 249,224us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= cli_TwoPointFiveZeroZeroPercentSeniorUnsecuredNotesDueDecemberFifteenTwoThousandSeventeenMember 		249,150us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= cli_TwoPointFiveZeroZeroPercentSeniorUnsecuredNotesDueDecemberFifteenTwoThousandSeventeenMember
Effective Rate 2.803%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_LongtermDebtTypeAxis
= cli_TwoPointFiveZeroZeroPercentSeniorUnsecuredNotesDueDecemberFifteenTwoThousandSeventeenMember 		[1]  
Interest rate of senior unsecured notes 2.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= cli_TwoPointFiveZeroZeroPercentSeniorUnsecuredNotesDueDecemberFifteenTwoThousandSeventeenMember 		 
Maturity date of the senior unsecured notes Dec. 15, 2017  
7.750% Senior Unsecured Notes, Due August 15, 2019 [Member]    
Debt Instrument [Line Items]    
Senior Unsecured Notes 249,066us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= cli_SevenPointSevenFiveZeroPercentSeniorUnsecuredNotesDueAugustFifteenTwoThousandNineteenMember 		249,013us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= cli_SevenPointSevenFiveZeroPercentSeniorUnsecuredNotesDueAugustFifteenTwoThousandNineteenMember
Effective Rate 8.017%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_LongtermDebtTypeAxis
= cli_SevenPointSevenFiveZeroPercentSeniorUnsecuredNotesDueAugustFifteenTwoThousandNineteenMember 		[1]  
Interest rate of senior unsecured notes 7.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= cli_SevenPointSevenFiveZeroPercentSeniorUnsecuredNotesDueAugustFifteenTwoThousandNineteenMember 		 
Maturity date of the senior unsecured notes Aug. 15, 2019  
4.500% Senior Unsecured Notes Due April 18, 2022 [Member]    
Debt Instrument [Line Items]    
Senior Unsecured Notes 299,580us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= cli_FourPointFiveZeroZeroPercentSeniorUnsecuredNotesDueAprilEighteenTwoThousandTwentyTwoMember 		299,565us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= cli_FourPointFiveZeroZeroPercentSeniorUnsecuredNotesDueAprilEighteenTwoThousandTwentyTwoMember
Effective Rate 4.612%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_LongtermDebtTypeAxis
= cli_FourPointFiveZeroZeroPercentSeniorUnsecuredNotesDueAprilEighteenTwoThousandTwentyTwoMember 		[1]  
Interest rate of senior unsecured notes 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= cli_FourPointFiveZeroZeroPercentSeniorUnsecuredNotesDueAprilEighteenTwoThousandTwentyTwoMember 		 
Maturity date of the senior unsecured notes Apr. 18, 2022  
3.150% Senior Unsecured Note, Due May 15, 2023 [Member]    
Debt Instrument [Line Items]    
Senior Unsecured Notes $ 270,082us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= cli_ThreePointOneFiveZeroPercentSeniorUnsecuredNotesDueMayFifteenthTwoThousandTwentyThreeMember 		$ 269,930us-gaap_UnsecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= cli_ThreePointOneFiveZeroPercentSeniorUnsecuredNotesDueMayFifteenthTwoThousandTwentyThreeMember
Effective Rate 3.517%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_LongtermDebtTypeAxis
= cli_ThreePointOneFiveZeroPercentSeniorUnsecuredNotesDueMayFifteenthTwoThousandTwentyThreeMember 		[1]  
Interest rate of senior unsecured notes 3.15%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= cli_ThreePointOneFiveZeroPercentSeniorUnsecuredNotesDueMayFifteenthTwoThousandTwentyThreeMember 		 
Maturity date of the senior unsecured notes May 15, 2023  
[1] Includes the cost of terminated treasury lock agreements (if any), offering and other transaction costs and the discount/premium on the notes, as applicable.