Mack-Cali Realty Corporation Stockholders' Equity (Stock Compensation) (Details) (USD $)
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Jan. 05, 2012
Jan. 05, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Restricted Stock Award vesting period, minimum (years) 1        
Restricted Stock Award vesting period, maximum (years) 7        
Common stock, shares outstanding 87,799,479 79,605,474   87,800,047 79,605,542
Shares, Outstanding, beginning balance 239,759 323,088 375,006    
Shares, Granted 81,736 [1] 111,127 [2] 83,337 [3]    
Shares, Vested (134,048) (170,978) (132,255)    
Shares, Forfeited   (23,478) (3,000)    
Shares, Outstanding ending balance 187,447 239,759 323,088    
Weighted-Average Grant-Date fair value, Outstanding beginning balance $ 35.90 $ 36.58 $ 34.46    
Weighted-Average Grant-Date fair value, Granted $ 25.38 [1] $ 32.10 [2] $ 32.27 [3]    
Weighted-Average Grant-Date fair value, Vested $ 32.39 $ 34.74 $ 27.55    
Weighted-Average Grant-Date fair value, Forfeited   $ 35.70 $ 49.61    
Weighted-Average Grant-Date fair value, Outstanding ending balance $ 33.82 $ 35.90 $ 36.58    
Restricted Stock [Member]
          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares, Outstanding ending balance 187,447 239,759 323,088    
Contingently Issuable Shares [Member]
          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Restricted stock awards unvested shares outstanding performance contingent 98,524        
Five Executive Officers [Member] | Restricted Stock [Member]
          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares, Granted     61,667    
Four Executive Officers [Member] | Restricted Stock [Member]
          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Shares, Granted 51,970 51,970      
[1] Included in the 81,736 Restricted Stock Awards granted in 2011 were 51,970 awards granted to the Company's four executive officers, Mitchell E. Hersh, Barry Lefkowitz, Roger W. Thomas and Michael Grossman.
[2] Included in the 111,127 Restricted Stock Awards granted in 2010 were 51,970 awards granted to the Company's four executive officers, Mitchell E. Hersh, Barry Lefkowitz, Roger W. Thomas and Michael Grossman.
[3] Included in the 83,337 Restricted Stock Awards granted in 2009 were 61,667 awards granted to the Company's five executive officers, Mitchell E. Hersh, Barry Lefkowitz, Roger W. Thomas, Michael Grossman and Mark Yeager.