Quarterly report pursuant to Section 13 or 15(d)

Commitments And Contingencies (Changes In Executive Officers) (Narrative) (Details)

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Commitments And Contingencies (Changes In Executive Officers) (Narrative) (Details) - USD ($)
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Commitments And Contingencies [Line Items]      
General and administrative $ 16,085,000 $ 11,592,000  
Accounts payable, accrued expenses and other liabilities 198,005,000   $ 192,716,000
Mack-Cali Realty LP [Member]      
Commitments And Contingencies [Line Items]      
General and administrative 16,085,000 $ 11,592,000  
Accounts payable, accrued expenses and other liabilities 198,005,000   $ 192,716,000
Messr Krug [Member]      
Commitments And Contingencies [Line Items]      
Severance benefits 1,312,500    
Prorated 2018 target bonus amount $ 93,750    
Messr Krug [Member] | Maximum [Member]      
Commitments And Contingencies [Line Items]      
Period for continuation of health insurance 2 years    
COBRA payment $ 42,000    
Messr DeLorenzo [Member]      
Commitments And Contingencies [Line Items]      
Severance benefits $ 500,000    
Period for continuation of health insurance 18 months    
Messr DeLorenzo [Member] | Maximum [Member]      
Commitments And Contingencies [Line Items]      
COBRA payment $ 42,000    
Messr Krug And Messr DeLorenzo [Member] | Employee Severance [Member]      
Commitments And Contingencies [Line Items]      
General and administrative 2,700,000    
Accounts payable, accrued expenses and other liabilities $ 2,100,000    
Time-Based Award [Member] | Messr Krug [Member] | Mack-Cali Realty LP [Member]      
Commitments And Contingencies [Line Items]      
Accelerated vesting shares 13,306    
Time-Based Award [Member] | Messr DeLorenzo [Member] | Mack-Cali Realty LP [Member]      
Commitments And Contingencies [Line Items]      
Partial accelerated vesting shares 9,111    
Performance Shares [Member] | Messr Krug [Member] | Mack-Cali Realty LP [Member]      
Commitments And Contingencies [Line Items]      
Accelerated vesting shares 18,665    
Performance Shares [Member] | Messr DeLorenzo [Member] | Mack-Cali Realty LP [Member]      
Commitments And Contingencies [Line Items]      
Partial accelerated vesting shares 13,982