Quarterly report pursuant to Section 13 or 15(d)

Segment Reporting (Selected Results Of Operations And Asset Information) (Details)

v2.4.1.9
Segment Reporting (Selected Results Of Operations And Asset Information) (Details) (USD $)
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Segment Reporting Information [Line Items]      
Total revenues $ 153,715,000us-gaap_RealEstateRevenueNet $ 169,596,000us-gaap_RealEstateRevenueNet  
Total operating and interest expenses 112,853,000cli_OperatingAndInterestExpenses [1] 141,004,000cli_OperatingAndInterestExpenses [1]  
Equity in earnings (loss) of unconsolidated joint ventures (3,529,000)us-gaap_IncomeLossFromEquityMethodInvestments (1,235,000)us-gaap_IncomeLossFromEquityMethodInvestments  
Net operating income (loss) 37,333,000cli_SegmentReportingInformationNetOperatingIncomeLossForReportableSegment [2] 27,357,000cli_SegmentReportingInformationNetOperatingIncomeLossForReportableSegment [2]  
Total assets 4,198,854,000us-gaap_Assets   4,192,247,000us-gaap_Assets
Total long-lived assets 3,664,450,000cli_LongLivedAssets [3]   3,670,704,000cli_LongLivedAssets [3]
Investments in unconsolidated joint ventures 262,052,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures   247,468,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
Real Estate - Commercial And Other [Member]      
Segment Reporting Information [Line Items]      
Total revenues 139,759,000us-gaap_RealEstateRevenueNet
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		157,520,000us-gaap_RealEstateRevenueNet
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		 
Total operating and interest expenses 72,198,000cli_OperatingAndInterestExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		[1] 86,933,000cli_OperatingAndInterestExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		[1]  
Equity in earnings (loss) of unconsolidated joint ventures (1,368,000)us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		988,000us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		 
Net operating income (loss) 66,193,000cli_SegmentReportingInformationNetOperatingIncomeLossForReportableSegment
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		[2] 71,575,000cli_SegmentReportingInformationNetOperatingIncomeLossForReportableSegment
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		[2]  
Total assets 3,627,443,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		  3,636,126,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember
Total long-lived assets 3,336,340,000cli_LongLivedAssets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		[3]   3,344,840,000cli_LongLivedAssets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		[3]
Investments in unconsolidated joint ventures 79,094,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember 		  81,649,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateCommercialAndOtherSegmentMember
Real Estate - Multi Family [Member]      
Segment Reporting Information [Line Items]      
Total revenues 6,584,000us-gaap_RealEstateRevenueNet
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		5,801,000us-gaap_RealEstateRevenueNet
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		 
Total operating and interest expenses 3,321,000cli_OperatingAndInterestExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		[1] 2,701,000cli_OperatingAndInterestExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		[1]  
Equity in earnings (loss) of unconsolidated joint ventures (2,161,000)us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		(2,223,000)us-gaap_IncomeLossFromEquityMethodInvestments
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		 
Net operating income (loss) 1,102,000cli_SegmentReportingInformationNetOperatingIncomeLossForReportableSegment
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		[2] 877,000cli_SegmentReportingInformationNetOperatingIncomeLossForReportableSegment
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		[2]  
Total assets 515,643,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		  492,362,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember
Total long-lived assets 321,295,000cli_LongLivedAssets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		[3]   318,524,000cli_LongLivedAssets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		[3]
Investments in unconsolidated joint ventures 182,554,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember 		  164,912,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
/ us-gaap_StatementBusinessSegmentsAxis
= cli_RealEstateMultipleFamilySegmentMember
Multi Family Services [Member]      
Segment Reporting Information [Line Items]      
Total revenues 8,232,000us-gaap_RealEstateRevenueNet
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		[4] 6,948,000us-gaap_RealEstateRevenueNet
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		[5]  
Total operating and interest expenses 9,655,000cli_OperatingAndInterestExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		[1] 10,159,000cli_OperatingAndInterestExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		[1]  
Net operating income (loss) (1,423,000)cli_SegmentReportingInformationNetOperatingIncomeLossForReportableSegment
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		[2] (3,211,000)cli_SegmentReportingInformationNetOperatingIncomeLossForReportableSegment
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		[2]  
Total assets 11,154,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		  11,158,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember
Total long-lived assets 3,811,000cli_LongLivedAssets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		[3]   3,858,000cli_LongLivedAssets
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		[3]
Investments in unconsolidated joint ventures 404,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		  907,000us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember
Fee revenue 1,300,000us-gaap_PropertyManagementFeeRevenue
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		800,000us-gaap_PropertyManagementFeeRevenue
/ us-gaap_StatementBusinessSegmentsAxis
= cli_MultipleFamilyServicesSegmentMember 		 
Corporate & Other [Member]      
Segment Reporting Information [Line Items]      
Total revenues (860,000)us-gaap_RealEstateRevenueNet
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember 		[6] (673,000)us-gaap_RealEstateRevenueNet
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember 		[6]  
Total operating and interest expenses 27,679,000cli_OperatingAndInterestExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember 		[1],[6] 41,211,000cli_OperatingAndInterestExpenses
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember 		[1],[6]  
Net operating income (loss) (28,539,000)cli_SegmentReportingInformationNetOperatingIncomeLossForReportableSegment
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember 		[2],[6] (41,884,000)cli_SegmentReportingInformationNetOperatingIncomeLossForReportableSegment
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember 		[2],[6]  
Total assets 44,614,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember 		[6]   52,601,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember 		[6]
Total long-lived assets $ 3,004,000cli_LongLivedAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember 		[3],[6]   $ 3,482,000cli_LongLivedAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_CorporateAndOtherMember 		[3],[6]
[1] Total operating and interest expenses represent the sum of: real estate taxes; utilities; operating services; direct construction costs; real estate services expenses; general and administrative and interest expense (net of interest income). All interest expense, net of interest and other investment income, (including for property-level mortgages) is excluded from segment amounts and classified in Corporate & Other for all periods.
[2] Net operating income represents total revenues less total operating and interest expenses (as defined in Note “a”), plus equity in earnings (loss) of unconsolidated joint ventures, for the period.
[3] Long-lived assets are comprised of net investment in rental property, unbilled rents receivable and goodwill.
[4] Includes $1.3 million of fees earned for this period from the multi-family real estate segment, which are eliminated in consolidation.
[5] Includes $0.8 million of fees earned for this period from the multi-family real estate segment, which are eliminated in consolidation.
[6] Corporate & Other represents all corporate-level items (including interest and other investment income, interest expense, non-property general and administrative expense, construction services revenue and direct construction costs) as well as intercompany eliminations necessary to reconcile to consolidated Company totals.