Commitments And Contingencies (Changes In Executive Officers) (Narrative) (Details) - USD ($)
 1 Months Ended 12 Months Ended
Jun. 05, 2018
Jun. 30, 2018
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Commitments And Contingencies [Line Items]          
Payment to former executive officers     $ 1,200,000    
General and administrative     53,988,000 $ 50,949,000 $ 51,979,000
Accounts payable, accrued expenses and other liabilities     168,115,000 $ 192,716,000  
Restructuring costs related to stock compensation     $ 1,000,000    
Shares granted     40,185 59,985 74,622
Common stock trading days     30 days    
Mack-Cali Realty LP [Member]          
Commitments And Contingencies [Line Items]          
General and administrative     $ 53,988,000 $ 50,949,000 $ 51,979,000
Accounts payable, accrued expenses and other liabilities     $ 168,115,000 $ 192,716,000  
Messr Rudin [Member]          
Commitments And Contingencies [Line Items]          
Severance benefits   $ 2,558,082      
Period for continuation of health insurance     18 months    
Payment of unreimbursed expenses   50,000      
COBRA payment   $ 34,047      
Accounts payable, accrued expenses and other liabilities     $ 23,000    
Restructuring costs related to stock compensation     1,600,000    
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    
Messr DeLorenzo [Member] | Mack-Cali Realty LP [Member]          
Commitments And Contingencies [Line Items]          
Partial accelerated vesting shares     9,111    
Messr DeLorenzo [Member] | Maximum [Member]          
Commitments And Contingencies [Line Items]          
Period for continuation of health insurance     18 months    
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     43,000    
Robert Andrew Marshall [Member]          
Commitments And Contingencies [Line Items]          
Consulting payment     22,500    
Payment to former executive officers     100,000    
COBRA payment     7,533    
Accounts payable, accrued expenses and other liabilities     1,000,000    
Restructuring costs related to stock compensation     $ 300,000    
Time-Based Award [Member] | Messr Rudin [Member] | Mack-Cali Realty LP [Member]          
Commitments And Contingencies [Line Items]          
Shares granted 32,311        
Time-Based Award [Member] | Messr Krug [Member] | Mack-Cali Realty LP [Member]          
Commitments And Contingencies [Line Items]          
Accelerated vesting shares     13,306    
Performance Shares [Member] | Messr Rudin [Member] | Mack-Cali Realty LP [Member]          
Commitments And Contingencies [Line Items]          
Shares granted 175,127        
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    
Vested 2016 Time-Based LTIP Awards [Member] | Robert Andrew Marshall [Member]          
Commitments And Contingencies [Line Items]          
Shares granted     22,120    
Vested 2016 Performance-Based LTIP Awards [Member] | Robert Andrew Marshall [Member]          
Commitments And Contingencies [Line Items]          
Shares granted     28,880    
Vested 2016 LTIP Awards [Member] | Robert Andrew Marshall [Member]          
Commitments And Contingencies [Line Items]          
Shares granted     35,697    
Shares to repurchase     51,000    
Common stock trading days     5 days    
Performance-Based LTIP Award Issued March 2016 [Member] | Robert Andrew Marshall [Member]          
Commitments And Contingencies [Line Items]          
Shares expired, forfeited or cancelled     6,817    
Time-Based LTIP Award Issued April 2017 [Member] | Robert Andrew Marshall [Member]          
Commitments And Contingencies [Line Items]          
Shares expired, forfeited or cancelled     4,449    
Performance-Based LTIP Award Issued April 2017 [Member] | Robert Andrew Marshall [Member]          
Commitments And Contingencies [Line Items]          
Shares expired, forfeited or cancelled     13,473    
Time-Based LTIP Award Issued April 2018 [Member] | Robert Andrew Marshall [Member]          
Commitments And Contingencies [Line Items]          
Shares expired, forfeited or cancelled     11,799    
Performance-Based LTIP Award Issued April 2018 [Member] | Robert Andrew Marshall [Member]          
Commitments And Contingencies [Line Items]          
Shares expired, forfeited or cancelled     22,676