Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies (Narrative) (Details)

v2.4.1.9
Significant Accounting Policies (Narrative) (Details) (USD $)
 0 Months Ended 3 Months Ended
Mar. 10, 2015
Dec. 09, 2014
Mar. 31, 2015
Mar. 31, 2014
Mar. 10, 2015
Dec. 31, 2014
Dec. 09, 2014
Significant Accounting Policies [Line Items]              
Capitalized development and construction salaries and other related costs     $ 1,300,000cli_CapitalizedDevelopmentConstructionSalariesAndOtherRelatedExpenses $ 900,000cli_CapitalizedDevelopmentConstructionSalariesAndOtherRelatedExpenses      
Construction, tenant improvement, and development in-progress     67,900,000us-gaap_ConstructionInProgressGross     62,800,000us-gaap_ConstructionInProgressGross  
Maximum period after cessation of major construction activity that projects are considered complete     1 year        
Threshold of investment value for discontinuation of equity method accounting     0cli_ThresholdOfInvestmentValueForDiscontinuationOfEquityMethodAccounting        
Amortization of deferred financing costs     953,000us-gaap_AmortizationOfFinancingCosts 769,000us-gaap_AmortizationOfFinancingCosts      
Write off of unamortized deferred financing costs     0us-gaap_WriteOffOfDeferredDebtIssuanceCost 0us-gaap_WriteOffOfDeferredDebtIssuanceCost      
Deferred leasing costs     970,000us-gaap_AmortizationOfDeferredLeasingFees 1,031,000us-gaap_AmortizationOfDeferredLeasingFees      
Deferred tax asset     15,200,000us-gaap_DeferredTaxAssetsValuationAllowance        
Income taxes, material adjustment amount     0cli_MaterialAdjustmentAmount        
Common stock, shares outstanding 88,918,291us-gaap_CommonStockSharesOutstanding 88,866,652us-gaap_CommonStockSharesOutstanding 89,127,942us-gaap_CommonStockSharesOutstanding   88,918,291us-gaap_CommonStockSharesOutstanding 89,076,578us-gaap_CommonStockSharesOutstanding 88,866,652us-gaap_CommonStockSharesOutstanding
Common units outstanding 11,036,898cli_CommonUnitsOutstanding 11,083,876cli_CommonUnitsOutstanding 11,036,898cli_CommonUnitsOutstanding   11,036,898cli_CommonUnitsOutstanding 11,083,876cli_CommonUnitsOutstanding 11,083,876cli_CommonUnitsOutstanding
Distributions payable, record date Apr. 06, 2015 Jan. 06, 2015          
Common stock dividends and common unit distributions per share $ 0.15cli_CommonStockDividendsAndCommonUnitDistributionsPerShare $ 0.15cli_CommonStockDividendsAndCommonUnitDistributionsPerShare          
Restricted stock expense     313,000us-gaap_RestrictedStockExpense 3,387,000us-gaap_RestrictedStockExpense      
Common stock dividends and common unit distributions payable, date Apr. 14, 2015 Jan. 14, 2015          
Difference between other comprehensive income and net income     0cli_DifferenceBetweenOtherComprehensiveIncomeAndNetIncomeLoss 0cli_DifferenceBetweenOtherComprehensiveIncomeAndNetIncomeLoss      
Accumulated other comprehensive income     0us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax     0us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax  
Executive Officer [Member]              
Significant Accounting Policies [Line Items]              
Restricted stock expense       $ 3,203,000us-gaap_RestrictedStockExpense
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= us-gaap_ExecutiveOfficerMember